TREND 2010 Agenda & Abstracts
Tuesday, June 15, NCAR/UCAR Center Green Campus| 8:00–9:00 | Registration, Continental Breakfast–(Lobby) |
| MORNING SESSION I (Chairman: S.C. Solomon) | |
| 9:00–9:30 |
Welcome talks by LOC, NCAR, J. Lastovicka (IAGA/ICMA WG), D. Marsh (CAWSES-II TG-2) Technical information/arrangements/logistic by LOC Special issue information by J. Emmert |
| Information on International Bodies: | |
| 9:30–9:45 | J. Lastovicka: IAGA/ICMA working group "Long-Term Trends in the Mesosphere, Thermosphere and Ionosphere" (invited) |
| 9:45–10:00 | D. Marsh, J. Lastovicka, G. Beig, U. Berger, S. Eckermann, J. Emmert, E. Manzini, C. Jacobi, J. Richter, K. Sato, G. Thomas, L. Qian: CAWSES-II - Task Group 2: How Will Geospace Respond to a Changing Climate? (invited) |
| 10:00–10:15 | M. Bittner, P. Espy, J. French, K. Hoeppner, J. Scheer, M.J. Taylor: The Network for the Detection of Mesopause Change (NDMC) (invited) |
| Solar and Geomagnetic Activity: | |
| 10:15–10:30 | V.K. Verma: On solar halo CMEs and its relation to solar activity phenomena and coronal holes observed during 1996-2007 |
| 10:30–11:00 | Morning Break |
| MORNING SESSION II (Chairman: A. Elias) | |
| 11:00–11:30 | J.L. Lean, J.T. Emmert: Solar spectral irradiance for studies of upper atmospheric climate change (invited) |
| 11:30–12:00 | K. Mursula: Long-term variability in geomagnetic activity and storminess: Implications for solar and heliospheric structure and development (invited) |
12:00–1:00 |
LUNCH BREAK |
| AFTERNOON SESSION I (Chairman: S. Yoden) | |
| 1:00–1:15 | V.K. Verma: On the long-term North-South Asymmetry of Solar Active Region Phenomena during Solar Cycles 6 to 24 |
| Overviews: | |
| 1:15–1:55 | J. Lastovicka: Progress in long-term trend investigations in the upper atmosphere and ionosphere (invited) |
| 1:55–2:35 | G.P. Brasseur: Anthropogenic versus Solar Forcing on the Chemical Composition of the Atmosphere: A Review (invited) |
| 2:35–3:05 | Afternoon Break |
| AFTERNOON SESSION II (Chairman: D. Marsh) | |
| 3:05–3:45 | L. Qian, S.C. Solomon, R.G. Roble: Modeling Efforts to Explain Observed Trends in the Upper Atmosphere and Ionosphere (invited) |
| Stratosphere: | |
| 3:45–4:15 | M. Baldwin: Trends and Stratosphere-Troposphere Coupling in a Changing Climate (invited) |
| 4:15–4:45 | J. Austin, J. Scinocca: Simulations of stratospheric ozone from 1960 to 2100 (invited) |
| 4:45–5:00 | G. Bodeker, Birgit Hassler: Global trends in total column ozone from natural and anthropogenic forcings: 1979 to 2009 |
5:00–6:30 |
RECEPTION |
There will be no scheduled poster sessions for the workshop. However, there will be poster boards in the lobby of NCAR/UCAR Center Green Campus through the entire workshop. You are welcome and encouraged to display posters there if you have one and would like to share with others.
TREND 2010 Abstracts
J. LastovickaTitle: LONG-TERM TRENDS IN THE MESOSPHERE, THERMOSPHERE AND IONOSPHERE
Abstract: The IAGA/ICMA (International Association of Geomagnetism and Aeronomy/International Commission on the Middle Atmosphere) working group (WG) "Long-Term Trends in the Mesosphere, Thermosphere and Ionosphere" has officially been established at the IUGG Assembly in Birmingham in 1999, even though preparation of the WG began at IAGA Assembly in Uppsala in 1997 as initiated by Gufran Beig. The purpose of the WG is to coordinate international activities in the area of long-term trends in the upper atmosphere and ionosphere via organizing specialized workshops, sessions at IAGA Assemblies, and organization of non-official task groups targeted to specific problems. Sessions at IAGA Assemblies have been held regularly once per two years since 1999. Special workshops were held in 1999 in Pune, India, in 2001 in Prague, Czech Republic, in 2004 in Sozopol, Bulgaria, in 2006 in Sodankyla, Finland, and in 2008 in St. Petersburg, Russia. The Boulder workshop is therefore the 6th workshop. The 7th workshop will be held in Argentina, Tucuman or Buenos Aires. Already four task groups have been establish and activity of each resulted in important publication(s): (1) Trends in mesospheric temperatures, (2) Comparison of various methods of calculating trends in F2-region parameters, (3) Creating scenario of long-term trends in the upper atmosphere and ionosphere, (4) Solar cycle effect on mesospheric temperatures. The paper will present more detailed information about all these activities.
D. Marsh
Title: CAWSES-II - TASK GROUP 2: HOW WILL GEOSPACE RESPOND TO A CHANGING CLIMATE?
Abstract: Climate and Weather of the Sun-Earth System (CAWSES-II) aims to coordinate efforts on "grand challenge" questions that can only be addressed through interdisciplinary research and international collaboration. The focus of Task Group 2, one of six Task Groups under CAWSES-II, will be to investigate the response of geospace to a changing climate. There is little doubt that the upper atmosphere is responding to rising greenhouse gas concentrations. Already patterns of cooling and contraction of the upper atmosphere are emerging from model studies and observations. Long-term satellite observations show significant trends in the distributions of NLC related to temperature trends and increasing methane concentrations. Additionally, it is likely that changes in the radiative, chemical, and dynamical forcing from below contribute to long-term upper atmosphere variability. In particular, if tropospheric gravity or planetary wave sources are affected by climate change, or if their filtering is modified as they propagate through a changing stratosphere, it is reasonable to expect the upper atmosphere will be modified in some way. This talk will introduce the projects under Task Group 2 that will focus on studying these changes and their underlying drivers. The projects will aim to answer the following questions over the next 4 years: (1). How do changes in tropospheric wave generation and their propagation through a changing atmosphere affect the dynamics of the MLT? (2). By how much is the anthropogenic effect on the ionosphere/thermosphere enhanced during a quiet sun period? (3). Are NLC characteristics trending?
M. Bittner
Title: THE NETWORK FOR THE DETECTION OF MESOPAUSE CHANGE (NDMC)
Abstract: The Network for the Detection of Mesopause Change (NDMC) is a global program with the mission to promote international cooperation among research groups investigating the mesopause region (80-100 km) with the goal of early identification of changing climate signals. This program involves the coordinated study of atmospheric variability at all time scales, the exchange of existing know-how, and the coordinated development of improved observation, analysis techniques and modeling. The initial emphasis is on mesopause region airglow techniques utilizing the existing ground-based and satellite measurement capabilities.
Participation or association of researchers using other techniques in the same altitude region will be actively developed. NDMC is concerned with coupling processes and will interface with related activities throughout the atmosphere. It is affiliated with the Global Atmosphere Watch program of the World Meteorological Organization and with the Network for the Detection of Atmospheric Composition Change.
V.K. Verma
Title: ON SOLAR HALO CMES AND ITS RELATION SOLAR ACTIVITY PHENOMENA AND CORONAL HOLES OBSERVED DURING 1996-2007
Abstract: In the present paper we have studied the reconnection of chromospheric active regions events and uni-polar regions (Coronal Holes/CH) leading to the production of solar coronal mass ejections (H-CMEs). To carry out this study we have used H-CMEs data for the period April 1996 and December 2007 observed by LASCO/ SOHO and the daily solar 10830 image observed at KPNO for the same period. We also used solar activity events data recorded by EIT instruments aboard SOHO, X-ray images of Sun recorded by Yohkoh mission, solar activity events recorded in H- Alpha emission from various ground based-based observatories and solar CH maps in 10830 A emissions recorded by KPNO, USA. To understand the role of CH maps in 10830 A and Chromospheric solar active region events we first matched time of onset of H-CMEs with time of solar events in H-alpha or EIT data. Secondly we looked for the spatial location of solar activity phenomena and CH maps on the solar disk. From this study we find that 45% H-CMEs were observed when there were CHs within 10 degree of flares locations, 25% H-CMEs were observed when there were CHs within 20 degree of flares locations, and 18% H-CMEs were observed when there were CHs within >20 and < 40 degree of flares locations. The flares locations are identified from H-alpha flares data or EIT activity phenomena. . We are of the view that the H-CMEs are perhaps have been produced by some mechanism, in which the mass ejected by some solar flares or active prominences, gets connected with the open magnetic lines of CHs (source of high speed solar wind streams) and moves along them to appear as suggested earlier by Verma and Pande (1989) and Verma(1998). In the present papers we will show reconnection between chromospheric flares or EIT activity phenomena and solar coronal holes area on the Sun.
J.L. Lean
Title: SOLAR SPECTRAL IRRADIANCE FOR STUDIES OF UPPER ATMOSPHERIC CLIMATE CHANGE
Abstract: Solar photons are Earth’s primary energy source. In the upper atmosphere, middle UV, far UV, and extreme UV irradiance are respectively the most important bands for the stratosphere, mesosphere/lower thermosphere, and upper thermosphere/ionosphere. Reliable, long-term estimates of solar spectral UV irradiance are therefore essential for studies of upper atmospheric climate change. Solar irradiance measurements must be made from space, and require instruments that are both accurate and precise. Because current measurement uncertainties are significantly larger than true solar irradiance variations a reliable database requires overlapping observations for cross-calibration. Furthermore, because the UV measurement record is temporally very limited, proxies are necessary to fill in gaps and extend the time series. In this presentation, we review current and future measurements, proxies, and models of spectral UV irradiance, and we assess their suitability for upper atmospheric trend studies. It is likely that F10.7 will remain the index of choice for most trend applications for many years, but the MgII index is emerging as another well calibrated index. We also demonstrate, with measurements of Earth’s atmosphere and ionosphere, the impact on trend studies of uncertainties in the long-term repeatability of solar irradiance measurements.
K. Mursula
Title: LONG-TERM VARIABILITY IN GEOMAGNETIC ACTIVITY AND STORMINESS: IMPLICATIONS FOR SOLAR AND HELIOSPHERIC STRUCTURE AND DEVELOPMENT
Abstract: Geomagnetic activity forms one of the most reliable and versatile ways to study the long-term change in the Sun and heliosphere. Continuous measurements of geomagnetic activity exist since the mid-19th century, covering nearly 170 years. In addition to the long-term trend, geomagnetic activity depicts persistent patterns and periodicities, the most dominant of which are the solar cycle variation and the semiannual variation. Other significant periodicities include the annual variation, 1.3-1.8-year variation and the 22-year variation. All these variations reflect fundamental properties of the Sun and the Sun-Earth connection. Interestingly, although some of these patterns are known for nearly 150 years, they are properly appreciated and understood only since recently. In this contribution I review the present status of the traditional and new indices of geomagnetic activity, discuss the present understanding of the systematic patterns reflected in geomagnetic activity, including the centennial change of geomagnetic activity and their implications on the long-term change of the Sun.
J. Lastovicka
Title: PROGRESS IN LONG-TERM TREND INVESTIGATIONS IN THE UPPER ATMOSPHERE AND IONOSPHERE
Abstract: The first scenario of observed long-term trends and/or global change in the upper atmosphere (mesosphere and thermosphere) and ionosphere has been constructed in 2006. The scenario consists of mutually consistent trends in mesospheric temperatures, thermospheric densities, upper ionosphere ion temperatures, and electron densities and heights of F1, E and D ionospheric layers. It demonstrates that anthropogenic emissions of greenhouse gases influence the atmosphere at nearly all altitudes between ground and space. Now we know that the greenhouse gases are the main driver of trends but other factors, namely stratospheric ozone depletion, middle atmosphere water vapour, long-term changes of geomagnetic activity and secular change of the Earth’s magnetic field play some role. However, there were three areas, characterized by key words F2 region, MLT (mesosphere and lower thermosphere) dynamics, middle atmosphere water vapour, which did not fit the above scenario of 2006. Recent progress with emphasis to the three above areas will be presented. According to recent model calculations and observational analyses, F2 region parameters foF2 and hmF2 could be at present dominantly controlled by geomagnetic activity and increasing concentration of greenhouse gases, respectively, or only by greenhouse gases, which removes part of contradictions. Relatively little progress has been reached in mesospheric dynamics; new data on trends in planetary wave activity remain controversial but indications of positive trend in the MLT region turbulence, which is thought to be produced by gravity wave dissipation, have been reported. As for mesospheric water vapour, there is strong indication that after considering different latitudes of satellite and ground-based NLC observations the difference between trends deduced from ground- and satellite-based data remains within limits given by the accuracy of observations, i.e. these measurements need not differ as it was thought earlier. Possible effect of solar activity will be mentioned briefly. Two key questions for future investigations are trends in MLT (or middle atmosphere) dynamics and links between trends in the upper atmosphere and stratosphere/troposphere.
V.K. Verma
Title: ON THE LONG-TERM NORTH-SOUTH ASYMMETRY OF SOLAR ACTIVE REGION PHENOMENA DURING SOLAR CYCLES 6 TO 24.
Abstract: In the solar N-S Asymmetry study we have used sunspots data, flare index data, H-alpha flares data and solar active prominences data for period 6-24 (years 1821-2010) solar cycles. Earlier Verma (1992) reported long-term cyclic period 11-12 solar cycles in N-S asymmetry and also predicted that the N-S asymmetry of solar activity phenomena during solar cycles 21, 22, 23 and 24 will be south dominated and the N-S asymmetry will shift to north hemisphere in solar cycle 25. The present study shows that the N-S asymmetry during solar cycles 22 and 23 are southern dominated as predicted by Verma (1992). The initial years (2008-2010) of solar cycle 24th are showing southern domination and confirm the result of Verma (1992). The 11 solar cycle’s periodic behavior of the Sun may be related to internal structure of the Sun.
G.P. Brasseur
Title: ANTHROPOGENIC VERSUS SOLAR FORCING ON THE CHEMICAL COMPOSITION OF THE ATMOSPHERE: A REVIEW
Abstract: Climate and atmospheric chemistry should be regarded as strongly coupled systems that are forced by solar variability as well as changes in surface emission of trace gases and particles. The paper will provide a review of our increasing understanding of the response of the atmospheric and climate systems to such forcing processes. It will highlight the role of models (including those developed by Ray Roble) for assessing the direct and indirect effects of natural and anthropogenic forcing mechanisms.
L. Qian
Title: MODELING EFFORTS TO EXPLAIN OBSERVED TRENDS IN THE UPPER ATMOSPHERE AND IONOSPHERE
Abstract: The observed global pattern of long-term trends in the upper atmosphere and ionosphere are as follows: cooling in the mesosphere, insignificant trend in the mesopause region, decrease of thermospheric neutral density with larger trends at solar minimum, increased electron density at fixed altitude in the lower ionosphere below 100 km, slight increase of E-region peak electron density and slight decrease of height of this peak, slight increase of electron density in the F1-region, , and decrease of F2-region ion temperature. Trends in the F2 region peak electron density (foF2) and height of this peak (hmF2) have been more complex and controversial. Large discrepancies and controversies remain between the results of different authors and different methods for trends of foF2 and hmF2. In order to facilitate observational detections of these long-term trends, simulations were performed using a coupled thermosphere-ionosphere- mesosphere general circulation model by imposing trends of CO2 concentrations. Trends of CO2 was used as the forcing in the model since CO2 is considered as a main greenhouse gas for the upper atmosphere. This paper will present model simulations results which show that the observed global pattern of long-term trends in the upper atmosphere and ionosphere can be qualitatively explained by the long-term trend of increase of CO2 concentrations, the resulting cooling and contraction of the upper atmosphere, and further long-term changes in upper atmospheric dynamics. Other sources of long-term trends in the upper atmosphere and ionosphere, such as long-term trends of the Earth’s main geomagnetic field, geomagnetic activity, stratospheric ozone concentrations, and mesospheric water vapor, can further refine explanations of the observed trends. This paper will also review modeling efforts on contributions of these sources of long-term trends in the upper atmosphere and ionosphere.
M. Baldwin
Title: TRENDS AND STRATOSPHERE-TROPOSPHERE COUPLING
IN A CHANGING CLIMATE
Abstract: The original concept of Southern and Northern Annular Modes (SAM, NAM; Thompson and Wallace, 1998, 2000) was for hemispheric variability of surface pressure observations. Their concept has been extended into the stratosphere, and has been condensed using analysis of zonal-mean data. Time-height cross-sections of the annular modes show the time-height development of stratosphere-troposphere coupling. However, there are challenges associated with the analysis of climate model projections as Earth’s climate changes. I will discuss methods to define annular modes that are consistent across observations and models, and are not significantly affected by the time period used to define the annular mode spatial patterns. This involves defining a slowly-varying climatology, rather than a fixed climatology. Analysis of Chemistry-Climate Models (CCMVal) suggests that the timescale and variability of the annular modes are not projected to change appreciably during the rest of this century. Stratosphere-troposphere coupling is also projected to change little.
J. Austin
Title: SIMULATIONS OF STRATOSPHERIC OZONE FROM 1960 TO 2100
Abstract: The long-term evolution of ozone is influenced by a wide variety of factors which may be broadly separated into radiative, dynamical, transport, chemical and external forcing processes. Many of the processes are also coupled in the sense that for example dynamical changes lead to chemical changes which feed back onto the dynamics. The degree to which all of these factors combined influence the future evolution of ozone will be shown using the simulations of the Chemistry Climate Validation 2 project. The two sets of results from experiments REF-B1 and REF-B2 will be used. In REF-B1, SSTs and external forcing parameters including the solar cycle, were specified from observations. In REF-B2, the GHG scenario SRES A1B and the halogen scenario A1 from WMO [2007] were used to investigate the future behaviour of stratospheric ozone until the end of the 21st century. The following key findings will be shown:
- The multi-model trend estimates of past ozone changes are consistent with the observed changes.
- Models consistently show ozone depletion prior to 1980, especially in the southern hemisphere.
- The effect of the increased strength of the circulation with time is to reduce tropical ozone and speed up ozone recovery especially in the northern hemisphere. (iv) In the models that simulate the current ozone hole well, a residual, albeit intermittent ozone hole remains at the end of the 21st century.
G. Bodeker
Title: GLOBAL TRENDS IN TOTAL COLUMN OZONE FROM NATURAL AND ANTHROPOGENIC FORCINGS: 1979 TO 2009
Abstract: A linear least squares regression model has been applied to an updated version of the NIWA combined total column ozone database to quantify the sources of trends and variability in total column ozone over the period 1979 to 2009. The regression model includes both natural (quasi-biennial oscillation, solar cycle, El Nino, volcanoes) and anthropogenic (stratospheric halogen loading, greenhouse gas loading) forcings and is applied to monthly mean total column ozone grids at 1.25 degree longitude and 1 degree latitude resolution to obtain global fields of regression model coefficients. The analysis updates previous studies but now (1) includes latitudinal differences in age-of-air and resultant differences in the shape of the equivalent effective stratospheric chlorine basis function, and (2) extends the analysis to the end of 2009 using a revised total column ozone database. A secondary goal of the paper is to evaluate regions and periods of largest regression model residuals with a view to identifying where inclusion of additional basis function in the model may improve the regression model fits.
N. Kilifarska
Title: DO WE UNDERSTAND THE DECADAL VARIABILITY OF THE OZONE LAYER?
Abstract: Multiple factorial analysis of the ozone layer reveals that besides the solar electromagnetic radiation, the energetic particles of solar and galactic origin have a significant influence on its interdecadal variability during the last five decades. The effect of the galactic energetic particles, also known as cosmic rays (CRs), is modulated by the 22 year heliomagnetic cycle, which controls their compositional structure. We found out that in 1970-ies and 1990-ies, when the heliomagnetic field was in its positive polarity and the dominant component of the CRs’ composition were protons and positively charged particles, the CRs’ influence manifested itself as a reduction of the stratospheric O3. This is due to the ozone destruction by the HOx and NOx destructive cycles, produced in situ in the stratosphere by deeply penetrating protons and alpha particles. When the heliomagnetic field is in its negative polarity (like in the 1960-ies, 1980-ies and the first decade of the 21st century) the dominant component of the CRs’ He+/e- ratio are electrons. They are adsorbed mainly in the upper atmosphere, forcing there strong ozone depletion through enhancement of HOx and NOx concentration. However, the depletion of the ozone column aloft forces a mechanism of odd oxygen production at lower levels (known as ozone self-healing). So in these decades an increase of the stratospheric ozone is detected. Analytical solution of the ozone balance equation allows us a quantitative estimation of the O3 dependence on its optical depth. Computational results confirm the idea that the lower stratospheric ozone may be significantly influenced by the mesospheric ozone depletion produced by high speed electrons and lower energetic protons. Comparison of the annually averaged O3 mass deficiency and Solar Proton Event fluxes shows that the solar protons decrease the ozone column density. Having in mind that the solar proton activity is higher during the periods of active Sun, it should to be stressed.
E. Savenkova
Title: VARIABILITY OF THE SPRING-TIME TRANSITION DATE AND PLANETARY WAVES IN THE BOREAL STRATOSPHERE
Abstract: The analysis of observations shows that there exists a strong interannual variability of the spring-time transition date of the stratospheric circulation. In the present study the year-to-year variability of the polar vortex breakup date and planetary waves in the Northern Hemisphere is examined on the base of data assimilated in the UK Met Office model. As a characteristic of the zonal mean flow the geostrophic wind calculated at 67.5°N using the geopotential heights of the 10 hPa pressure level has been used. The results obtained show a significant correlation of the spring-time transition date with the observed planetary-wave activity in the lower stratosphere. There is a positive tendency (secular trend) in the spring-time transition date (of about 9 days per decade) during 1992-2009 years.
S. Yoden
Title: LONG-TERM TRENDS IN STRATOSPHERIC TEMPERATURE AND THEIR DETECTABILITY IN FUTURE SIMULATIONS UNDER THE SITUATION OF LARGE NATURAL VARIABILITY
Abstract: Recent reports on updates of observed stratospheric temperature trends are reviewed, as well as those on coupled chemistry-climate model simulations of the trends. Mean cooling trends in the middle and upper stratosphere derived from updated SSU data were about 0.5–1.5 K/decade during 1979–2005, while temperature anomalies were relatively constant during the decade 1995–2005 throughout the stratosphere. The climatology of coupled chemistry climate models for the recent past is in good agreement with observations for the troposphere but the model results diverge from each other and from observations in the stratosphere. Differences in model formulation and in the simulation of ozone trends likely contribute to the spread in calculated lower stratospheric temperature trends. Natural variability in the dynamics is reflected in model performance in the Arctic stratosphere. An ensemble experiment with a simple global circulation model was done to estimate the detectability of a cooling trend in the stratosphere from a limited length data set with such large internal variability; necessary magnitude of the trend to be detected significantly can be obtained for a given data length.
K. Semeniuk
Title: ROLE OF IONIZING PARTICLE PRECIPITATION IN THE SOLAR CYCLE OF THE MIDDLE ATMOSPHERE
Abstract: We conduct ensemble runs with the Canadian Middle Atmosphere Model to investigate the effect of energetic particle precipitation (EPP; auroral electrons, solar proton events and galactic cosmic rays) on dynamics and chemical composition. Cases with and without the solar cycle in heating and photolysis rates are considered. It is found that particle precipitation modulates the atmospheric response to solar cycle evolution especially in the southern hemisphere in spite of being a relatively small effect. EPP affects the ozone distribution and hence the evolution of the polar vortex through the modification of the radiative equilibrium temperature and wave drag. The impact is not confined to the polar regions and extends to the tropics where there is an enhancement of the cold point tropopause temperature variation with the solar cycle.
R. Garcia
Title: DETERMINATION OF AGE-OF-AIR TRENDS FROM CHEMICAL TRACE SPECIES
Abstract: Trace chemical species have been used in numerical models to calculate the age of air (AOA) and its trend. The latter is found to be negative in simulations where greenhouse gases (GHG) increase with time, a result that is consistent with the trend in the modeled mean meridional circulation, which accelerates under these conditions. Recently, this model prediction has been tested experimentally using observations of SF6, a very long lived species whose atmospheric concentration has increased rapidly over the last half century, and of CO2, which is also very long lived and increasing with time. Surprisingly, the AOA estimated from these gases exhibits no trend since the 1970s. However, we show that the absence of a trend in the AOA derived from SF6 is reproduced in simulations carried out with the Whole Atmosphere Community Climate Model. We show further, by means of a simplified global transport model and analytical arguments, that this follows from the non-linear and variable growth rate of SF6, and that similar problems exist for CO2.
S.K. Sharma
Title: IMPRINT OF GREENHOUSE COOLING IN LIDAR OBSERVED MIDDLE ATMOSPHERIC TEMPERATURE TRENDS OVER A SUB-TROPICAL LOCATION, MT. ABU (24.5°N, 72.7°E)
Abstract: In recent years there has been great concern of greenhouse effect in the atmosphere due to increased anthropogenic activities and its consequences in the global climate. Roble and Dickinson (1989) examined the consequences for the middle/upper atmosphere due to the increased concentration of trace gases, using a global mean model and reported cooling in middle and upper atmosphere for the first time. For more than two decades, Lidar has become a dynamic atmospheric probe for providing height profile of density/temperature in the middle atmospheric region. A Nd: YAG laser based Rayleigh Lidar was set up, at a high altitude observatory near Mount Abu (24.5°N, 72.7°E, altitude1.7 km), in the Indian sub-tropical region, to study the Earth’s neutral atmospheric temperature structure. The system is transmitting pulses of 7 ns duration at a frequency of 10 Hz with average power about 350 mJ at 532 nm. For the study of temperature climatology in the stratosphere, we have used the Rayleigh lidar data collected for about 11 years from 1997 to 2008. The systematic and statistical errors in deriving temperature are found to be less than ~1 K below 50 km. For the study of long term changes in the thermal structure, consistently good data series for 1997–2008 has been investigated. Monthly mean temperature profiles for each month individually have been used to remove seasonal variability. A multivariable analysis is used to consider natural variability (Solar Cycle and QBO) and similarly the changes in stratospheric ozone concentration due to anthropogenic activity have also been taken into account in trends estimations. We have selected different height regions 30–40, 40–50 and 50–60 km for trends analysis. Linear Regression analysis is applied to calculate temperature trend in different altitude regions. Considering the signature of seasonal, QBO and solar cycle variability, a linear decreasing temperature (cooling) has been found. Observed temperature trend is the strongest (-0.33 ± 0.16 K/year) at stratopause level (45 km) and the weakest (-0.15 ± 0.32 K/year) at 55 km during April. Seasonally, stronger temperature trends are found during winter -4.2±2.5, -4.8±2.4 and -2.0±2.1 K/decade at 35, 45 and 55 km, respectively. The temperature trends during summer months are -2.1±2.0, -2.6±1.8 and -2.3±2.7 K/decade at 35, 45 and 55 km, respectively. Lidar observed temperature trends over Mt. Abu are also compared with HALOE (onboard UARS) temperature observations.
H. Schmidt
Title: NUMERICAL SIMULATION OF THE MLT RESPONSE TO NATURAL AND ANTHROPOGENIC FORCING FOR THE PERIOD 1960 TO 2006
Abstract: The region of the mesosphere and lower thermosphere (MLT) links the more dynamically controlled lower and middle atmosphere with the upper atmosphere that is influenced strongly by external forcing of in particular solar origin. Consequently, in the MLT, it is often difficult to assess if signals are related to either local processes (e.g. of varying absorption of solar radiation or changing concentrations of radiatively active gases) or related to dynamical changes in the lower atmosphere that are influencing the region due to changes in propagation conditions of waves. Additionally, long observational time series for the mesopause region are rare, covering, in general, not more than two or three solar cycles. Hence, observed variability and trends in such time series are difficult to attribute unambiguously to a particular forcing type. Numerical simulations can provide a useful tool to better understand the possible role of these different phenomena. Here, we analyze different simulations with the general circulation and chemistry model HAMMONIA for the period 1960 to 2006. The simulations are performed according to the REF1b simulation protocol of the CCMVAL model intercomparison activity, and include the major external forcings observed for this period. It is analyzed, which part of the simulated variability in the mesopause region can be attributed to solar forcing, GHG concentration changes, ENSO, volcanic eruptions, or internal atmospheric variability related to the QBO. Results are compared to available observations, and it is studied how the attribution of simulated signals is affected if only subsets of the full time series are used for the analysis. Furthermore correlations between signals in the stratosphere and the MLT are analyzed to assess the importance of vertical propagation of signals.
A.K. Smith, R.R. Garcia, D.R. Marsh
Title: TRENDS IN TRANSPORT OF TRACE GASES BETWEEN THE THERMOSPHERE AND MIDDLE ATMOSPHERE
Abstract: Transport of trace gases can change with time due to long term changes in the sources of the gases or to trends in the circulation, diffusion, or other transport processes. For this study, we use multi-decade integrations of the NCAR Whole Atmosphere Community Climate Model (WACCM) to investigate the transport of trace species between the thermosphere and middle atmosphere since 1960. The focus is on variations in the high latitude upward and downward transport during solstice seasons. We consider species with significant concentration changes in the MLT region: NO, CO, CO2, O, and H. Hemispheric differences in the trends and comparisons with observations are also shown.
J. T. Emmert, J. M. Picone, J. L. Lean
Title: WHITHER THE THERMOSPHERE? INTERPRETATION OF ORBIT-DERIVED DENSITY TRENDS FROM 1967 THROUGH THE UNUSUAL 2008 SOLAR MINIMUM
Abstract: We use global-average thermospheric total mass density, derived from the drag effect on the orbits of many space objects, to deduce updated density trends from 1967 through 2009. Based on the height dependence of these trends, we estimate corresponding changes in exospheric temperature and thermospheric composition. During the cycle 23/24 solar minimum of 2008, thermospheric densities were the lowest observed in over 40 years of measurements, and were anomalously low (by 10–30% at a height of 400 km) compared to levels expected from past climatological behavior during the previous two minima. They were also much lower than expected from extrapolation of previous linear trend estimates. These anomalies appear to have started in 2005. We estimate the contributions of thermospheric temperature and composition perturbations to the observed density anomalies, and discuss potential solar and geo-atmospheric causes..
H. Lewis
Title: UNDERSTANDING THE CONSEQUENCES OF A LONG-TERM DECLINE IN THERMOSPHERIC DENSITY ON THE NEAR-EARTH SPACE DEBRIS ENVIRONMENT
Abstract: Historically, computer simulations of the near-Earth space debris environment have provided a basis for international debris mitigation guidelines and, today, continue to influence international debate on debris environment remediation and Active Debris Removal (ADR). Approximately 19,000 objects larger than 10 cm are known to exist in Earth orbit and less than 10% of these are operational payloads, with the remaining population classed as space debris. These objects represent a significant risk to satellite operations, due to the possibility of damaging or catastrophic collisions, as demonstrated by the collision between Iridium 33 and Cosmos 2251 in February 2009. Indeed, recent computer simulations have suggested that the current population in Low Earth Orbit (LEO) has reached a sufficient density at some altitudes for collision activity there to continue even in the absence of new launches. Even with the widespread adoption of debris mitigation guidelines, the growth of the LEO population, in particular, is expected to result in eight or nine collisions among catalogued objects in the next 40 years. With a new study using the University of Southampton’s high-fidelity space debris model, entitled DAMAGE, we show the effectiveness of current debris mitigation and future remediation strategies will decrease by up to 40% due to a long-term future decline in global thermospheric density. In addition, the cost of key strategies that rely on the use of atmospheric drag will increase, as more propellant or greater cross-sectional surface area (for example) is required to meet mitigation requirements. This “double blow” has important consequences for future discussions of space debris remediation and the form of new guidelines designed to address the continuing growth of the space debris population.
A. Saunders
Title: FURTHER EVIDENCE OF LONG-TERM THERMOSPHERIC DENSITY CHANGE USING A NEW METHOD OF SATELLITE BALLISTIC COEFFICIENT ESTIMATION
Abstract: Building on the work from Saunders et al. (2009) in conjunction with the findings of Emmert et al. (2008) a strong case is presented for the existence of a long-term density change in the Thermosphere. In a similar manner using a bespoke orbital propagator to predict satellite orbit evolution, combined with a new and accurate method of determining satellite ballistic coefficients, a long-term Thermospheric density change has been detected using a different method to previous studies. Over a 30-year period between the years 1970 and 2010, Thermospheric density has appeared to reduce by a few percent per decade. However, the results do not show the Thermospheric density reduction to vary linearly with time. Therefore, by performing a Fourier Spectral analysis to highlight periodicities present in the results, connections with physical phenomena are proposed. There are many ways of determining atmospheric density, but inferring thermospheric density from satellite drag data is a relatively cost-effective way of gathering in-situ measurements. Given an initial satellite orbit, one approach is to use an orbital propagator to predict the satellites state at some time ahead and then to compare that state with Two-Line Element (TLE) data at the same epoch. The difference between the semi-major axis of the satellite from the initial orbit and that after the orbit propagation is then integrated to obtain an estimate of global average density. This is the approach adopted in our new work, using a bespoke, orbital propagator that includes perturbations due to atmospheric drag, gravitational anomalies, luni-solar gravity effects and solar radiation pressure. The methods used to derive precise estimates of the ballistic coefficient of each satellite for use in the propagator are outlined, as this information is not contained explicitly in the TLE sets. Now, historical satellite data from the past 40 years have been used to infer Thermospheric density values over the same period. A comparison of these values with those derived from an empirical standard atmospheric model, the US NRLMSISE-00 (Naval Research Laboratory’s Mass Spectrometry and Incoherent Scatter Radar up to the Exobase, released in the year 2000), is the method by which the long-term trend is established.
S. Solomon, L. Qian, T. N. Woods
Title: THE SOLAR ACTIVITY MINIMUM BETWEEN CYCLES 23 AND 24: IMPLICATIONS FOR QUANTIFYING THERMOSPHERIC TRENDS
Abstract: Solar activity during 2007–2009 was extremely low, including ultraviolet irradiance, solar wind parameters, and the interplanetary magnetic field. During this protracted solar minimum period, the terrestrial upper atmosphere and ionosphere were cooler, lower in density, and consequently lower in altitude, than usual. The question remains as to whether the terrestrial response to this solar minimum is significantly different from previous solar minima, and if so, how different. Measurements from the SEM instrument on SOHO spacecraft, from the SEE instrument on the TIMED satellite, and from measurements by suborbital rocket flights, indicate that solar extreme-ultraviolet and soft X-ray irradiance levels were lower they were during the previous solar minimum. In order to understand the causes of these changes, and to quantify the interplay of the solar cycle with the evolution of upper atmosphere and ionosphere climate, we present a combination of data analysis and global numerical simulation. Thermospheric density data from atmospheric drag on satellites, ionospheric measurements by the COSMIC mission and from ground-based sources, and cooling rate data from the SABER instrument on the TIMED mission, are compared to model simulations by the NCAR Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM). Solar ultraviolet irradiance observations, solar wind and geomagnetic data, and measurements of anthropogenic greenhouse gases, provide the external forcing of the model. The response to the recent solar minimum is compared to previous solar minima, and to model simulations. We find compelling evidence that the thermosphere was cooler during 2008 than any other year for which measurements exist (back to about 1970), and that the primary reason for this is the unusually low levels of solar extreme-ultraviolet and soft X-ray irradiance. The implications for quantifying anthropogenic secular change in thermospheric temperatures and densities, given a fuller understanding of the differences in solar forcing between different solar minima, are discussed.
S. Nossal
Title: GEOCORONAL HYDROGEN: THE UNIVERSITY OF WISCONSIN’S LONG-TERM DATA SET
Abstract: The University of Wisconsin has observed geocoronal hydrogen Balmer-alpha emissions since the late 1970s from Wisconsin and during Solar Cycle 23 from the Kitt Peak, AZ observatory. These observations were all obtained using ground-based double etalon Fabry-Perot Interferometers. The signal-to-noise of the observations has increased along with the sensitivity of the instrumentation. Earlier observations used scanning photomultiplier detection, and the Solar Cycle 23 observations employed CCD annular summing spectroscopy. We are using this long-term data set to investigate the impact of the solar cycle variation upon upper atmospheric hydrogen, a byproduct of radiatively important water vapor and methane below. Understanding natural variability is important for characterizing the upper atmosphere and for isolating potential signs of anthropogenic change due to changes in methane and carbon dioxide concentrations. The Wisconsin Northern hemisphere mid-latitude data set shows consistent solar cycle dependence over two solar cycles and three solar minima with column emission intensities a factor of ~1.5 higher during solar maximum than solar minimum conditions. We review the Wisconsin long-term data record, including sources of uncertainty, calibration, and work in progress to link the Solar Cycle 22 and Solar Cycle 23 observations, taken with different modes of detection. We also present ongoing efforts to compare these observations to empirical and climate models of the upper atmosphere.
S. Zhang
Title: LONG-TERM TRENDS IN THE UPPER ATMOSPHERIC TEMPERATURE OBSERVED BY INCOHERENT SCATTER RADAR AT MILLSTONE HILL
Abstract: After decades of operations, incoherent scatter radar (ISR) observational datasets are now available for detecting and studying long-term trends of the upper atmosphere. ISRs have the capability of monitoring the thermal status of the upper atmosphere by measuring the ionospheric ion and electron temperatures as well as electron density over a broad height range from the E region to the F region. In this presentation, we will report noontime ion temperature results within 200-500 height range. This study is based on over 30 years’ ISR observation at Millstone Hill (42.6°N, 288.5°E). It is indicated that a clear temperature cooling trend prevails in the F region, and the cooling becomes increasingly significant with height. This pattern of height dependency is very similar to theoretical results given by Roble and Dickinson [1989]. The exospheric temperature at noon is estimated to decrease at ~3% per decade.
A.G. Elias
Title: TRENDS IN THE EQUATORIAL F2 REGION DUE TO SECULAR VARIATIONS IN THE EARTH’S MAGNETIC FIELD
Abstract: Dynamics play a fundamental role in the equatorial ionosphere. In particular, during daytime in the equatorial F2 region, the eastward electric field (E) combined with the Earth’s magnetic field (B) drives a vertical plasma fountain at the magnetic equator creating the Equatorial Ionization Anomaly (EIA) characterized by an electron density trough at the magnetic dip equator with crests at 15° to 20° to the north and south. The EIA characteristics should vary then with the secular changes of B and of the dip equator geographic latitude. Considering the long-term variation in B and the dip equator movement since 1956, the trends induced in foF2 and hmF2 at latitudes around the trough and crests of the EIA, are analyzed together with the expected changes in the EIA pattern.
G. Beig
Title: RECENT ADVANCES IN LONG TERM TRENDS OF MLT-REGION
Abstract: During the past one decade, significant advancement has been made to understand the long term trends caused due to anthropogenic activities and that of natural variability lead by solar activity variations. A global picture of the temperature response to GHGs increase and solar activity in the mesosphere and lower thermospheric region has also been made available in review articles (Beig et al., Rev. Geophys., 2003, 2008). However, still there are some occasions where the temperature trend results indicate inconsistency with respect to geography, period of analysis and seasons. There used to be a growing number of experimental results centered on, or consistent with zero temperature trends in the mesopause region which is not true in recent time. The most reliable data sets still show no significant trend, but with an uncertainty of at least 2K/decade. It is also increasingly clear that until the solar-related changes in the long term temperature series are well understood and quantified in the mesosphere, there is little hope of separating out changes due to longer-term secular variability caused due to human induced changes at the surface, much less gaining any insight into their causes. The discrepancy in the solar signal of temperature obtained by experimental data and the model results over the equatorial regions is still unresolved. In this talk, an update of the long-term trend and solar signal in temperature of the region from 50–100 km has been made based on available understanding. The question of break in trend as a result of ozone recovery is briefly touched upon. However, now the major challenge is in the interpretation of the various reported results which are diverse and even indicates latitudinal variability.
D. Krueger, C.-Y. She
Title: UNCERTAINTIES IN MESOPAUSE TEMPERATURE TRENDS
Abstract: Assessing long-term temperature trends from 17 years of sodium-lidar measurements in the mesopause region has been carried out by fitting the data to a combination of non-orthogonal functions of time including a solar effect, a volcanic eruption effect, annual and semiannual variations as well as the trend. Determination of the uncertainties in the parameters is complicated by not knowing the uncertainties of the individual measurements due to the presence of short-term geophysical variations such as gravity waves, tides and planetary waves in addition to experimental uncertainties due to photon noise. Two methods have been used. In the first, one assigns a uniform uncertainty to all temperature measurements and then fixes this by assuming that the fitting model is good and setting the chi-square to the number of observations minus the number of parameters determined. The second method, bootstrap Monte Carlo, does not require the assumption that the model is good, but does assume independent and identically distributed data points. It determines the distribution of the coefficients from fitting sets of data obtained from re-sampling the original data set for time-temperature pairs with replacement. The two methods give essentially the same values and standard deviations of the fit parameters.
F.-J. Luebken, U. Berger, J. Kiliani, G. Baumgarten, J. Fiedler, Michael Gerding
Title: SOLAR CYCLE AND LONG TERM VARIATIONS OF MESOSPHERIC ICE LAYERS
Abstract: Ice layers in the summer mesosphere at middle and polar latitudes
frequently called “noctilucent clouds” (NLC) or “polar mesosphere clouds”(PMC) are considered to be sensitive indicators of long term changes in the middle atmosphere. We present a summary of long term observations from the ground and from satellites and compare with results from the LIMA model (Leibniz Institute Middle Atmosphere Model). LIMA nicely reproduces mean conditions of the summer mesopause region and also mean characteristics of ice layers. LIMA nudges to ECMWF data in the troposphere and lower stratosphere which influences the background conditions in the mesosphere and thereby the morphology of ice clouds.
A strong correlation between temperatures and PMC altitudes is observed. Applied to historical measurements this gives negligible temperature trends at PMC altitudes (approximately 0.01-0.02 K/y). In a first step trace gas concentrations were kept constant in LIMA except for water vapor which is modified by variable solar radiation. Still, long term trends in temperatures and ice layer parameters are observed, consistent with observations. As will be shown, these trends originate in the stratosphere.
In a next step we included long term changes of trace gases in the mesosphere. We will present results from these new calculations. Solar cycle effects are expected in ice layers due to variations in background temperatures and water paper. In LIMA we model the impact of solar radiation and ice particles on mesospheric H2O. More recently we have included variations of the background temperatures due to solar activity.
We will present results from LIMA regarding solar cycle variations and trends and will compare these resuults with NLC observations at our lidar stations in Kühlungsborn (54°N) and ALOMAR (69°N), and also with satellite measurements.
M. DeLand, E. Shettle, G. Thomas, J. Olivero
Title: LONG-TERM VARIATIONS REVEALED IN SBUV PMC DATA
Abstract: Polar mesospheric clouds (PMCs) are a valuable source of information about the upper atmosphere. We have combined satellite measurements since 1978 from seven different SBUV and SBUV/2 instruments to create a 31-year data record of PMC behavior. Multiple regression analysis of this data set shows that PMC occurrence frequency and brightness are anti-correlated with long-term solar activity in both hemispheres, and that secular increases in these quantities are also seen. Recent 3-D atmospheric model calculations reproduce many aspects of the long-term PMC variations observed by SBUV. However, the relative importance of mesospheric temperature and water vapor changes in these results is still under investigation. Dynamical activity also plays a role, as evidenced through local time dependence effects and interannual variations that is yet to be fully defined. We will discuss our latest results in characterizing the forcing mechanisms that are responsible for the long-term changes in the SBUV PMC data.
M. Grygalashvyly
Title: TRENDS AND STABILITY IN THE MLT-REGION: A MODEL STUDY
Abstract: The height of the NLC has not noticeably declined since the time of first observation. The term "equithermal submesopause" was introduced in 1996 and reflects the significant repeatability of the mean mesopause temperature during the last 40 years. The microwave measurements of water vapor at high latitudes (ALOMAR, 69°N) during last 14 years do not show significant positive trends in MLT-region. These facts motivate us to study the mechanisms of stabilization in the atmosphere and precisely in the summer mesopaus region which is astonishingly stable in spite of the anthropogenic changes. We investigate the influence of the rising concentrations of methane, nitrous oxide and carbon dioxide since 1961 on the chemistry of the mesosphere. We use our global 3D-model LIMA (Leibniz-Institute Middle Atmosphere) designed for the investigation of the MLT-region and particularly the extended mesopause region. LIMA uses real tropospheric and lower stratospheric temperature and horizontal wind up to 35 km altitude from assimilation of ECMWF/ERA-40. Real time Lyman ± flux values are employed to determine the water vapor dissociation rate. The analysis of the long-term behavior of water vapor also utilizes real methane measurements. The solar influence on the water vapor mixing ratio is insignificant below about 75–80 km within high latitudes in summer, but becomes increasingly important above this domain. Three calculations were carried out and analyzed: a) with dependence on yearly varying dynamics and anthropogenic grow of green house gases, b) the same but with "constant" dynamics and with anthropogenic changes, and, c) with varying dynamics but without anthropogenic changes. The analyses of these 3 cases show, that the effect of dynamics reduces the influence of anthropogenic changes in the upper mesosphere-mesopause-lower thermosphere region. This probably occurs due to non-linear feed backs effect between dynamics and chemistry. Therefore, models with climatologically mean dynamics, apparently, overestimate anthropogenic impact. We also discuss the long-term behavior of water vapor with regard to the potential impact on NLC.
C. Jacobi
Title: LONG-TERM TRENDS AND THEIR CHANGES IN MLT WINDS AND WAVES AT MIDLATITUDES
Abstract: Long-term variability of mesosphere/lower thermosphere (MLT) winds, tidal amplitudes and phases, and long-period oscillations has been analyzed using ground-based wind data series obtained at Collm (52°N, 15°E), Obninsk (55°N, 37°E) and Saskatoon (52°N, 107°E) applying different radar methods. Applying piecewise linear trend analysis with a priori unknown number, positions and types of breakpoints shows that trend models with breakpoints are frequently preferred against straight lines. There is indication for a change of trends in some MLT dynamical parameters in the 1990s. Since similar changes are also found in the lower and middle atmosphere, visible, e.g., in tropospheric circulation patterns, ozone, and temperatures. This indicates a coupling between atmospheric layers at time scales of decades.
P. Hoffmann
Title: SEASONAL AND INTERANNUAL VARIATION OF MESOSPHERIC WAVES AT MIDDLE AND HIGH LATITUDES
Abstract: The seasonal and interannual variation of the wave activity in the mesosphere/lower thermosphere (MLT) at middle and high latitudes is investigated on the basis of nearly identical wind measurements with meteor and MF radars at Juliusruh (55°N, 13°E) and Andenes (69°N, 16°E). The interpretation of the annual cycle at both latitudes is based on the simulation annual cycle using the mechanistic general circulation model KMCM which reproduces the main observed features very well. For the observations, proxies for the activity of mid-frequency gravity waves (GWs) and waves with longer periods are computed from their variances estimated as sum of wavelets for defined bandwidths. The corresponding proxy for the simulated GWs is the non-rotational kinetic energy due to the resolved mesoscales. Both observational and computational results show the strongest GW energy during winter and a secondary maximum during summer. This semi-annual variation is consistent with directional GW filtering by the annual cycle of the mean zonal wind. The latitudinal dependence during summer is characterized by stronger GW energy below about 82 km at middle latitudes than at polar latitudes, and a corresponding upward shift of the wind reversal towards the pole which is also reflected by the simulated GW drag. Mesospheric wind measurements are available at Juliusruh since 1990. First results of long term investigations at middle latitudes indicate a negative trend of the zonal winds below 80 km during summer. This increase of the observed westward directed winds during July goes along with an enhanced gravity wave activity at altitudes above 80 km. These results for middle latitudes will be compared with the data derived at Andenes since 1999.
K. Hoeppner, M. Bittner
Title: CLIMATOLOGY OF TEMPERATURE OSCILLATIONS WITH PERIODS OF 3–20 DAYS DERIVED FROM OH(3-1) OBSERVATIONS AT THE NDMC-STATION WUPPERTAL (51°N, 7°E), GERMANY
Abstract: Prominence cavities are rarefied regions of the corona which overlie polar crown prominences. Cavities are inherently a difficult structure to diagnose, but they likely hold the key to understanding the formation and stability of prominences. This work focuses on the use of the Hinode Extreme ultraviolet Imaging Spectrometer to deduce the plasma properties inside the cavity. One notable result is the identification of large scale flows inside of cavities. The relationship between these coronal flows and the cooler, smaller scale prominence flows has yet to be determined.
M. Mlynczak, L. Hunt, J. Mast
Title: OBSERVATIONS OF NATURAL VARIABILITY IN THE MESOSPHERE-THERMOSPHERE CLIMATE SYSTEM FROM THE TIMED/SABER INSTRUMENT—AND A VIEW TO THE FUTURE
Abstract: The TIMED/SABER instrument is providing an unprecedented look at fundamental elements of the climate system of the mesosphere and thermosphere. With a data record now at 8.5 years, SABER data are quantifying the natural variability of the mesosphere and thermosphere due to solar activity and to interactions with the atmosphere below. SABER observes the thermal structure, chemical composition, and most importantly for climate, infrared radiative cooling. These data provide a key first step in assessing possible long-term climate change. The results also suggest a new approach for measuring long-term climate change in the mesosphere and thermosphere from satellites. Specifically, a long-term, accurately calibrated time series of infrared limb emission should provide direct evidence of the expected cooling of the thermosphere and mesosphere. Averages over large time and space scales should reveal a long-term decrease in infrared emission associated with a cooler mesosphere and thermosphere, due to the non-linear relationship between temperature and infrared cooling. These concepts will be presented as forming possible elements of a space-based upper atmosphere climate observing system.
N. Kilifarska
Title: DO WE UNDERSTAND THE DECADAL VARIABILITY OF THE OZONE LAYER?
Abstract: Multiple factorial analysis of the ozone layer reveals that besides the solar electromagnetic radiation, the energetic particles of solar and galactic origin have a significant influence on its interdecadal variability during the last five decades. The effect of the galactic energetic particles, also known as cosmic rays (CRs), is modulated by the 22 year heliomagnetic cycle, which controls their compositional structure. We found out that in 1970-ies and 1990-ies, when the heliomagnetic field was in its positive polarity and the dominant component of the CRs’ composition were protons and positively charged particles, the CRs influence manifested itself as a reduction of the stratospheric O3. This is due to the ozone destruction by the HOx and NOx destructive cycles, produced in situ in the stratosphere by deeply penetrating protons and alpha particles. When the heliomagnetic field is in its negative polarity (like in the 1960-ies, 1980-ies and the first decade of the 21st century) the dominant component of the CRs’ He+/e- ratio are electrons. They are adsorbed mainly in the upper atmosphere, forcing there strong ozone depletion through enhancement of HOx and NOx concentration. However, the depletion of the ozone column aloft forces a mechanism of odd oxygen production at lower levels (known as ozone self-healing). So in these decades an increase of the stratospheric ozone is detected. Analytical solution of the ozone balance equation allows us a quantitative estimation of the O3 dependence on its optical depth. Computational results confirm the idea that the lower stratospheric ozone may be significantly influenced by the mesospheric ozone depletion produced by high speed electrons and lower energetic protons.
S. Wüst, M. Bittner
Title: SEPARATION OF CHEMICALLY AND DYNAMICALLY INDUCED OZONE TRENDS IN WINTERLY NORTHERN LATITUDES
Abstract: The 25 year TOMS ozone data series (1978–2005) in the Northern Hemisphere is investigated with respect to longitudinal and latitudinal dependant trends. Sinusoidal structures in the longitudinal trend behaviour are interpreted in terms of planetary wave activity. This is in agreement with an observed trend in the amplitudes of the planetary waves with zonal wave number 1 and 2. These trends are found to clearly vary with month and latitude. This effect is used to separate chemically and dynamically induced ozone trends. It is discussed how the background ozone concentration in midlatitudes might be influenced by streamer events caused by breaking planetary waves.
E. Savenkova, A. Pogoreltsev, E. Merzlyakov
Title: VARIABILITY OF THE SPRING-TIME TRANSITION DATE AND PLANETARY WAVES IN THE BOREAL STRATOSPHERE
Abstract: The analysis of observations shows that there exists a strong interannual variability of the spring-time transition date of the stratospheric circulation. In the present study the year-to-year variability of the polar vortex breakup date and planetary waves in the Northern Hemisphere is examined on the base of data assimilated in the UK Met Office model. As a characteristic of the zonal mean flow the geostrophic wind calculated at 67.5°N using the geopotential heights of the 10 hPa pressure level has been used. The results obtained show a significant correlation of the spring-time transition date with the observed planetary-wave activity in the lower stratosphere. There is a positive tendency (secular trend) in the spring-time transition date (of about 9 days per decade) during 1992–2009 years.
S. Yoden
Title: LONG-TERM TRENDS IN STRATOSPHERIC TEMPERATURE AND THEIR DETECTABILITY IN FUTURE SIMULATIONS UNDER THE SITUATION OF LARGE NATURAL VARIABILITY
Abstract: Recent reports on updates of observed stratospheric temperature trends are reviewed, as well as those on coupled chemistry-climate model simulations of the trends. Mean cooling trends in the middle and upper stratosphere derived from updated SSU data were about 0.5–1.5 K/decade during 1979–2005, while temperature anomalies were relatively constant during the decade 1995–2005 throughout the stratosphere. The climatology of coupled chemistry climate models for the recent past is in good agreement with observations for the troposphere but the model results diverge from each other and from observations in the stratosphere. Differences in model formulation and in the simulation of ozone trends likely contribute to the spread in calculated lower stratospheric temperature trends. Natural variability in the dynamics is reflected in model performance in the Arctic stratosphere. An ensemble experiment with a simple global circulation model was done to estimate the detectability of a cooling trend in the stratosphere from a limited length data set with such large internal variability; necessary magnitude of the trend to be detected significantly can be obtained for a given data length.
K. Semeniuk
Title: ROLE OF IONIZING PARTICLE PRECIPITATION IN THE SOLAR CYCLE OF THE MIDDLE ATMOSPHERE
Abstract: We conduct ensemble runs with the Canadian Middle Atmosphere Model to investigate the effect of energetic particle precipitation (EPP; auroral electrons, solar proton events and galactic cosmic rays) on dynamics and chemical composition. Cases with and without the solar cycle in heating and photolysis rates are considered. It is found that particle precipitation modulates the atmospheric response to solar cycle evolution especially in the southern hemisphere in spite of being a relatively small effect. EPP affects the ozone distribution and hence the evolution of the polar vortex through the modification of the radiative equilibrium temperature and wave drag. The impact is not confined to the polar regions and extends to the tropics where there is an enhancement of the cold point tropopause temperature variation with the solar cycle.
R. Garcia, W. Randel, D. Kinnison
Title: DETERMINATION OF AGE-OF-AIR TRENDS FROM CHEMICAL TRACE SPECIES
Abstract: Trace chemical species have been used in numerical models to calculate the age of air (AOA) and its trend. The latter is found to be negative in simulations where greenhouse gases (GHG) increase with time, a result that is consistent with the trend in the modeled mean meridional circulation, which accelerates under these conditions. Recently, this model prediction has been tested experimentally using observations of SF6, a very long lived species whose atmospheric concentration has increased rapidly over the last half century, and of CO2, which is also very long lived and increasing with time. Surprisingly, the AOA estimated from these gases exhibits no trend since the 1970s. However, we show that the absence of a trend in the AOA derived from SF6 is reproduced in simulations carried out with the Whole Atmosphere Community Climate Model. We show further, by means of a simplified global transport model and analytical arguments, that this follows from the non-linear and variable growth rate of SF6, and that similar problems exist for CO2.
S. Sharma, H. Chandra, S. Lal, Y. B. Acharya
Title: IMPRINT OF GREENHOUSE COOLING IN LIDAR OBSERVED MIDDLE ATMOSPHERIC TEMPERATURE TRENDS OVER A SUB-TROPICAL LOCATION, MT. ABU (24.5°N, 72.7°E)
Abstract: In recent years there has been great concern of greenhouse effect in the atmosphere due to increased anthropogenic activities and its consequences in the global climate. Roble and Dickinson (1989) examined the consequences for the middle/upper atmosphere due to the increased concentration of trace gases, using a global mean model and reported cooling in middle and upper atmosphere for the first time. For more than two decades, Lidar has become a dynamic atmospheric probe for providing height profile of density/temperature in the middle atmospheric region. A Nd: YAG laser based Rayleigh Lidar was set up, at a high altitude observatory near Mount Abu (24.5°N, 72.7°E, altitude1.7 km), in the Indian sub-tropical region, to study the Earth’s neutral atmospheric temperature structure. The system is transmitting pulses of 7 ns duration at a frequency of 10 Hz with average power about 350 mJ at 532 nm. For the study of temperature climatology in the stratosphere, we have used the Rayleigh Lidar data collected for about 11 years from 1997 to 2008. The systematic and statistical errors in deriving temperature are found to be less than ~1 K below 50 km. For the study of long term changes in the thermal structure, consistently good data series for 1997–2008 has been investigated. Monthly mean temperature profiles for each month individually have been used to remove seasonal variability. A multivariable analysis is used to consider natural variability (Solar Cycle and QBO) and similarly the changes in stratospheric ozone concentration due to anthropogenic activity have also been taken into account in trends estimations. We have selected different height regions 30–40, 40–50 and 50–60 km for trends analysis. Linear Regression analysis is applied to calculate temperature trend in different altitude regions. Considering the signature of seasonal, QBO and solar cycle variability, a linear decreasing temperature (cooling) has been found. Observed temperature trend is the strongest (-0.33 ± 0.16 K/year) at stratopause level (45 km) and the weakest (-0.15 ± 0.32 K/year) at 55 km during April. Seasonally, stronger temperature trends are found during winter -4.2 ± 2.5, -4.8 ± 2.4 and -2.0 ± 2.1 K/decade at 35, 45 and 55 km, respectively. The temperature trends during summer months are -2.1 ± 2.0, -2.6 ± 1.8 and -2.3 ± 2.7 K/decade at 35, 45 and 55 km, respectively. Lidar observed temperature trends over Mt. Abu are also compared with HALOE (onboard UARS) temperature observations.
G. Beig
Title: RECENT ADVANCES IN LONG TERM TRENDS OF MLT-REGION
Abstract: During the past one decade, significant advancement has been made to understand the long term trends caused due to anthropogenic activities and that of natural variability lead by solar activity variations. A global picture of the temperature response to GHGs increase and solar activity in the mesosphere and lower thermospheric region has also been made available in review articles (Beig et al., Rev. Geophys., 2003, 2008). However, still there are some occasions where the temperature trend results indicate inconsistency with respect to geography, period of analysis and seasons. There used to be a growing number of experimental results centered on, or consistent with zero temperature trends in the mesopause region which is not true in recent time. The most reliable data sets still show no significant trend, but with an uncertainty of at least 2K/decade. It is also increasingly clear that until the solar-related changes in the long term temperature series are well understood and quantified in the mesosphere, there is little hope of separating out changes due to longer-term secular variability caused due to human induced changes at the surface, much less gaining any insight into their causes. The discrepancy in the solar signal of temperature obtained by experimental data and the model results over the equatorial regions is still unresolved. In this talk, an update of the long-term trend and solar signal in temperature of the region from 50–100 km has been made based on available understanding. Thshee question of break in trend as a result of ozone recovery is briefly touched upon. However, now the major challenge is in the interpretation of the various reported results which are diverse and even indicates latitudinal variability.
C.-Y. She, D.A. Krueger
Title: LONG-TERM VARIABILITY IN MESOPAUSE REGION NOCTURNAL TEMPERATURES OVER FORT COLLINS, COLORADO (41°N, 105°W)
Abstract: Mesopause region temperatures over Fort Collins, CO (40.6°N, 105°W) have been observed by a narrowband Na lidar since 1990. Regression analyses of the nightly averaged temperatures over nearly two decade duration are analyzed for the deduction of the long-term temperature trend and the 11-year solar-cycle effect, along with an episodic response after Mount Pinatubo eruption in 1991. While the cooling trend can be as much as 7 K/decade when the episodic response is ignored, its inclusion yields a cooling trend in the region with a maximum cooling of ~1.5 K/decade at 91 km, turning to a small warming trend above ~102 km. The observed magnitude and altitude dependences of the trend so analyzed are consistent with the prediction of two general circulation models, SMLTM and HAMMONIA. To draw a parallel, this prolonged episode response, not yet fully understood, will be compared to a recently published analysis of surface temperature changes after the Mount Pinatubo eruption.
T. Li
Title: TEMPERATURE TREND AND SOLAR CYCLE REVEALED FROM RAYLEIGH LIDAR OBSERVATIONS
Abstract: The long-term temperature datasets obtained by Rayleigh lidars at five different locations from low to high latitudes within the Network for the Detection of Atmospheric Composition Change (NDACC) were used to derive the temperature trend and temperature response to 11-year solar cycle in the middle atmosphere: Mauna Loa Observatory, Hawaii (MLO, 19.5°N); Table Mountain Facility, California (TMO, 34.4°N); Observatoire de Haute Provence, France (OHP, 43.9°N); Hohenpeissenberg, Germany (HOH, 47.8°N); Sondre Stromfjord, Greenland (SFJ, 67.0°N). The temperature response to 11-year solar cycle was observed to be positive at both MLO and OHP in the stratosphere, and positive at MLO and TMO and negative at OHP in the mesosphere. The small cooling trend was observed in the upper stratosphere and lower mesosphere at MLO, while large cooling trend of ~2–4K/decade was observed at TMO throughout the altitude region. The lidar observed temperature response to 11-year solar cycle and temperature trend in the middle atmosphere were in generally consistent with early observations and model simulations.
D.A. Krueger, C.-Y. She
Title: UNCERTAINTIES IN MESOPAUSE TEMPERATURE TRENDS
Abstract: Assessing long-term temperature trends from 17 years of sodium-lidar measurements in the mesopause region has been carried out by fitting the data to a combination of non-orthogonal functions of time including a solar effect, a volcanic eruption effect, annual and semiannual variations as well as the trend. Determination of the uncertainties in the parameters is complicated by not knowing the uncertainties of the individual measurements due to the presence of short-term geophysical variations such as gravity waves, tides and planetary waves in addition to experimental uncertainties due to photon noise. Two methods have been used. In the first, one assigns a uniform uncertainty to all temperature measurements and then fixes this by assuming that the fitting model is good and setting the chi-square to the number of observations minus the number of parameters determined. The second method, bootstrap Monte Carlo, does not require the assumption that the model is good, but does assume independent and identically distributed data points. It determines the distribution of the coefficients from fitting sets of data obtained from re-sampling the original data set for time-temperature pairs with replacement. The two methods give essentially the same values and standard deviations of the fit parameters.
F.-J. Luebken, U. Berger, J. Kiliani, G. Baumgarten, J. Fiedler, M. Gerding
Title: SOLAR CYCLE AND LONG TERM VARIATIONS OF MESOSPHERIC ICE LAYERS
Abstract: Ice layers in the summer mesosphere at middle and polar latitudes frequently called “noctilucent clouds” (NLC) or “polar mesosphere clouds”(PMC) are considered to be sensitive indicators of long term changes in the middle atmosphere. We present a summary of long term observations from the ground and from satellites and compare with results from the LIMA model (Leibniz Institute Middle Atmosphere Model). LIMA nicely reproduces mean conditions of the summer mesopause region and also mean characteristics of ice layers. LIMA nudges to ECMWF data in the troposphere and lower stratosphere which influences the background conditions in the mesosphere and thereby the morphology of ice clouds.
M. DeLand, E. Shettle, G. Thomas, J. Olivero
Title: LONG-TERM VARIATIONS REVEALED IN SBUV PMC DATA
Abstract: Polar mesospheric clouds (PMCs) are a valuable source of information about the upper atmosphere. We have combined satellite measurements since 1978 from seven different SBUV and SBUV/2 instruments to create a 31-year data record of PMC behavior. Multiple regression analysis of this data set shows that PMC occurrence frequency and brightness are anti-correlated with long-term solar activity in both hemispheres, and that secular increases in these quantities are also seen. Recent 3-D atmospheric model calculations reproduce many aspects of the long-term PMC variations observed by SBUV. However, the relative importance of mesospheric temperature and water vapor changes in these results is still under investigation. Dynamical activity also plays a role, as evidenced through local time dependence effects and interannual variations that is yet to be fully defined. We will discuss our latest results in characterizing the forcing mechanisms that are responsible for the long-term changes in the SBUV PMC data.
M. Grygalashvyly, G. R. Sonnemann, U. Berger, F.-J. Luebken
Title: TRENDS AND STABILITY IN THE MLT-REGION: A MODEL STUDY
Abstract: The height of the NLC has not noticeably declined since the time of first observation. The term "equithermal submesopause" was introduced in 1996 and reflects the significant repeatability of the mean mesopause temperature during the last 40 years. The microwave measurements of water vapor at high latitudes (ALOMAR, 69°N) during last 14 years do not show significant positive trends in MLT-region. These facts motivate us to study the mechanisms of stabilization in the atmosphere and precisely in the summer mesopaus region which is astonishingly stable in spite of the anthropogenic changes. We investigate the influence of the rising concentrations of methane, nitrous oxide and carbon dioxide since 1961 on the chemistry of the mesosphere. We use our global 3D-model LIMA (Leibniz-Institute Middle Atmosphere) designed for the investigation of the MLT-region and particularly the extended mesopause region. LIMA uses real tropospheric and lower stratospheric temperature and horizontal wind up to 35 km altitude from assimilation of ECMWF/ERA-40. Real time Lyman ± flux values are employed to determine the water vapor dissociation rate. The analysis of the long-term behavior of water vapor also utilizes real methane measurements. The solar influence on the water vapor mixing ratio is insignificant below about 75–80 km within high latitudes in summer, but becomes increasingly important above this domain. Three calculations were carried out and analyzed: a) with dependence on yearly varying dynamics and anthropogenic grow of green house gases, b) the same but with "constant" dynamics and with anthropogenic changes, and, c) with varying dynamics but without anthropogenic changes. The analyses of these 3 cases show, that the effect of dynamics reduces the influence of anthropogenic changes in the upper mesosphere-mesopause-lower thermosphere region. This probably occurs due to non-linear feed backs effect between dynamics and chemistry. Therefore, models with climatologically mean dynamics, apparently, overestimate anthropogenic impact. We also discuss the long-term behavior of water vapor with regard to the potential impact on NLC.
C. Jacobi
Title: LONG-TERM TRENDS AND THEIR CHANGES IN MLT WINDS AND WAVES AT MIDLATITUDES
Abstract: Long-term variability of mesosphere/lower thermosphere (MLT) winds, tidal amplitudes and phases, and long-period oscillations has been analyzed using ground-based wind data series obtained at Collm (52°N, 15°E), Obninsk (55°N, 37°E) and Saskatoon (52°N, 107°E) applying different radar methods. Applying piecewise linear trend analysis with a priori unknown number, positions and types of breakpoints shows that trend models with breakpoints are frequently preferred against straight lines. There is indication for a change of trends in some MLT dynamical parameters in the 1990s. Since similar changes are also found in the lower and middle atmosphere, visible, e.g., in tropospheric circulation patterns, ozone, and temperatures. This indicates a coupling between atmospheric layers at time scales of decades
P. Hoffmann
Title: SEASONAL AND INTERANNUAL VARIATION OF MESOSPHERIC WAVES AT MIDDLE AND HIGH LATITUDES
Abstract: The seasonal and interannual variation of the wave activity in the mesosphere/lower thermosphere (MLT) at middle and high latitudes is investigated on the basis of nearly identical wind measurements with meteor and MF radars at Juliusruh (55°N, 13°E) and Andenes (69°N, 16°E). The interpretation of the annual cycle at both latitudes is based on the simulation annual cycle using the mechanistic general circulation model KMCM which reproduces the main observed features very well. For the observations, proxies for the activity of mid-frequency gravity waves (GWs) and waves with longer periods are computed from their variances estimated as sum of wavelets for defined bandwidths. The corresponding proxy for the simulated GWs is the non-rotational kinetic energy due to the resolved mesoscales. Both observational and computational results show the strongest GW energy during winter and a secondary maximum during summer. This semi-annual variation is consistent with directional GW filtering by the annual cycle of the mean zonal wind. The latitudinal dependence during summer is characterized by stronger GW energy below about 82 km at middle latitudes than at polar latitudes, and a corresponding upward shift of the wind reversal towards the pole which is also reflected by the simulated GW drag. Mesospheric wind measurements are available at Juliusruh since 1990. First results of long term investigations at middle latitudes indicate a negative trend of the zonal winds below 80 km during summer. This increase of the observed westward directed winds during July goes along with an enhanced gravity wave activity at altitudes above 80 km. These results for middle latitudes will be compared with the data derived at Andenes since 1999.
K. Hoeppner
Title: CLIMATOLOGY OF TEMPERATURE OSCILLATIONS WITH PERIODS OF 3–20 DAYS DERIVED FROM OH(3-1) OBSERVATIONS AT THE NDMC-STATION WUPPERTAL (51°N, 7°E), GERMANY
Abstract: A time series of nightly mean OH(3-1) temperature measurements from 1987 to 2009 are analysed with respect to planetary wave activity. The observations were taken with the IR-spectrometer GRIPS-2 (Ground-based Infrared P-branch Spectrometer) at the NDMC-station Wuppertal (51°N, 7°E), Germany. After removing seasonal trends from the data record using the harmonic analysis, temperature fluctuations with periods of 3–20 days are calculated with the wavelet analysis. Data gaps are interpolated using the maximum entropy method in its capacity as a linear prediction filter. A climatology of the occurrence of these shorter period oscillations revealing seasonal structures is presented.
M. Mlynczak, L. Hunt, J. Mast
Title: OBSERVATIONS OF NATURAL VARIABILITY IN THE MESOSPHERE-THERMOSPHERE CLIMATE SYSTEM FROM THE TIMED/SABER INSTRUMENT — AND A VIEW TO THE FUTURE
Abstract: The TIMED/SABER instrument is providing an unprecedented look at fundamental elements of the climate system of the mesosphere and thermosphere. With a data record now at 8.5 years, SABER data are quantifying the natural variability of the mesosphere and thermosphere due to solar activity and to interactions with the atmosphere below. SABER observes the thermal structure, chemical composition, and most importantly for climate, infrared radiative cooling. These data provide a key first step in assessing possible long-term climate change. The results also suggest a new approach for measuring long-term climate change in the mesosphere and thermosphere from satellites. Specifically, a long-term, accurately calibrated time series of infrared limb emission should provide direct evidence of the expected cooling of the thermosphere and mesosphere. Averages over large time and space scales should reveal a long-term decrease in infrared emission associated with a cooler mesosphere and thermosphere, due to the non-linear relationship between temperature and infrared cooling. These concepts will be presented as forming possible elements of a space-based upper atmosphere climate observing system.
A.G. Elias, M.Z. de Artigas, B.F. de Haro Barbas
Title: LONG-TERM VARIATIONS IN Sq RELATED TO GREENHOUSE GASES AND EARTH’S MAGNETIC FIELD
Abstract: Trends in the solar quiet geomagnetic field variation, Sq, are studied in connection to greenhouse gases increasing concentration and secular variations of the Earth’s magnetic field. Sq variations are a manifestation of ionospheric current systems which flow in the E-region. These currents depend on ionospheric conductivities, which vary with the Earth’s main magnetic field, B, and the electron concentration in the E region, for which foE is a measure of its peak value. B presents secular variations linked to changes in the Earth’s core flow and foE, an increasing trend due to the increasing concentration in greenhouse gases. Based on these facts, a theoretical approximation is first made to assess the expected trends in Sq induced by B secular variations and greenhouse gases increasing concentration. To detect these trends, the Sq variation of the horizontal intensity, H, of magnetic observatories at low and mid-latitudes are analyzed. We find significant trends which may be partially accounted by B secular variations in the respective sites and also by foE trend due to greenhouse gases increasing concentration.
C. Jacobi
Title: THE SEASONAL VARIABILITY OF IONOSPHERIC PLANETARY WAVE TYPE OSCILLATIONS IN THE COURSE OF THE SOLAR CYCLE
Abstract: Planetary wave type oscillations (PWTO) analyzed through space-time frequency analysis from differential Total Electron Content (dTEC) at midlatitudes (52.5°N) show a seasonal cycle similar to those of stratospheric planetary waves (PW). Signatures of PW from below become apparent on the winter hemisphere probably through indirect processes as, e.g., modulation of gravity waves. Nearly continuously, there is a strong winter and weak summer activity of ionospheric PWTO observed during 2002–2008, appropriate to stratospheric PW. A proxy of travelling PW and PWTO, combining mean and standard deviation of a parameter in the longitude-time domain is used to provide general picture of wave activity. PWTO activity is stronger during solar maximum than during solar minimum. Considering the interannual variability of the seasonal cycle of PWTO, the transition from low to high dTEC wave activity in autumn occurs earlier and high wave activity persists longer during solar maximum than around solar minimum.
S.K. Sharma, H. Chandra
Title: LONG TERM MODIFICATIONS IN THE IONOSPHERE AT LOW LATITUDES: IMPACT OF GREENHOUSE GASES
Abstract: Roble and Dickinson (1989) were first to examine the response of the upper atmosphere to the increased concentration of greenhouse gases and reported a cooling of 10 K and 50 K in mesosphere and thermosphere respectively due to doubling of CO2 and CH4 at 60 km. Rishbeth and Roble (1992) made calculations of the changes in ionosphere due to cooling using the NCAR TIGC (Thermosphere/Ionosphere General Circulation) model. Lowering of the F2 layer peak by about 15 km, on an average, decreases in foF2, of 0.5 MHz at the most were predicted by them. The calculations showed a decrease in electron densities in the topside and a increase in the bottomside (below 200–250 km for low and below 300–350 km for high solar activity periods). We report here the changes in ionosphere observed at two low latitude stations Ahmedabad (23.1°N), situated at the northern crest of Equatorial Ionization Anomaly region, and Kodaikanal (10.2°N), near the magnetic equator. Ionospheric data over Ahmedabad during the period 1955–2004 are analysed. Critical frequencies of the E, F1 and F2 layers and the parameter hpF2 (a measure of the height of F2 layer peak) have been examined for the study of long term ionospheric trends. To remove seasonal variation data are examined for each month separately. Solar cycle variation is removed following the method of Bremer (1992), and trends obtained using both the sunspot number Rz and the 10.7 cm solar flux. The foF2 data at Kodaikanal for 1960–95 are used to estimate the trends. The annual trends for Ahmedabad show a decrease in foF2 of about 1.8 MHz in five decades for midday and about 1.3 MHz for midnight. The lowering of F2 peak by about 12 km during midday and about 14 km during midnight are also observed in this period. An increase of 0.5 MHz in foF1 in about five decades is noted. The results are in agreement with the model predictions of Rishbeth and Roble (1992). Seasonally the changes are least for summer months. The foF2 at Kodaikanal an equatorial station shows a decrease of about 0.6 MHz for midday and 0.8 MHz for midnight in four decades. The results are significant considering the errors in estimation of the trends and the errors in scaling of the ionospheric parameters.
B.M. Vyas, V. Saraswat
Title: LONG-TERM TRENDS IN THE IONOSPHERIC D REGION HF RADIOWAVES ABSORPTION MEASUREMENTS OVER INDIAN LOW LATITUDE UDAIPUR
Abstract: Study of long term changes in several lower and upper atmospheric parameters over the different parts of the Earth’s globe has attracted the lot of attention in recent decades due to its great importance and possible links with current scientific environmental issues of global climate changes. Extensive atmospheric modeling and experimental finding show that the increasing concentration of atmospheric green house gases due to both anthropogenic and natural activities cause a cooling of the lower and upper ionosphere and warming of troposphere. Serafimov and Serafimova suggested the measurements of HF radio waves absorption in the ionosphere would be the most sensitive indicators of possible climate changes in the ionosphere or possible anthropogenic influences on the mesosphere and lower thermosphere or ionospheric D– region. As HF radio waves absorptions basically depends upon electron density and electron- neutral collision frequency, which, in turns, is a function of neutral temperature and neutral density. Therefore, in the present investigation, an attempt has been made in studying the long term changes in the lower ionospheric parameter using the ionospheric D- region radiowaves absorption data collected over Indian low latitude station i.e., Udaipur (Geo.Lat. 24.6°N, Geo. Long. 73.7°E) using A-1 Pulse radio wave reflection method during year from year 1972 to 1984. The monthly values of the ionospheric radio waves absorption data series for 12 years are generated for particular solar zenith angle as well as for fixed solar radio fluxes ( solar activity ) for adopting the appropriate regression analysis. The calculated monthly absorption data at fixed solar zenith angles and at constant solar activity level are plotted with years for each month separately from year 1972 to 1984. The similar plot of measurement of concentration of Atmospheric Carbon Dioxide data for the low latitude are also plotted . The details of the results would be presented.
S. Molodykh, G. Zherebtsov, V. Kovalenko
Title: THE INFLUENCE OF SOLAR ACTIVITY ON LONG-TERM CHANGE OF TROPOSPHERE CHARACTERISTICS
Abstract: Mechanisms of solar activity effects on weather and climate have been discussed. Authors proposed a physical mechanism of solar activity effects on climatic characteristics and the atmospheric circulation through the atmospheric electricity. A model of the solar activity effect on climatic characteristics of the Earth’s troposphere was elaborated on the basis of the mechanism under consideration. The model key concept is the heliogeophysical disturbance effect on the Earth climatic system’s parameters, which influence energy flux going from the Earth to space in high-latitude areas. According to our model, when the solar activity increases, radiation cooling of high-latitude regions decreases, thermobaric field restructures, average meridian gradient of temperature between polar and equatorial regions decreases, defining the atmospheric circulation. In the framework of the model considered, the analysis results are presented and discussed of regularities of variations in geomagnetic activity and troposphere thermobaric characteristics for 1900–2007. It was shown that observable long-term changes in troposphere characteristics are generally caused by changes in the underlying surface. It can be explained by the fact that the accumulation of individual heliogeophysical disturbance effects occurs in the underlying surface (mainly in the ocean). The continuous increase of the Earth climatic system heat content has been observed from 1910 till now. Under the model, we made analysis of regularities, which underlie variations of geomagnetic activity and troposphere thermobaric characteristics. These results and changes of the global circulation in the atmosphere and ocean allow the conclusion that the warming observed in the 20th century can be mostly explained by variations of the solar activity level. Scenario for long-term changes of physical processes in the Earth atmosphere, cryosphere and ocean is presented on the basis of the model of the solar activity effect on the troposphere circulation and thermobaric characteristics.
J.-Y. Liu, Y.-I. Chen, T.-W. Fang
Title: SEVERE WEATHER IN CHINA LINKED TO LONG-TERM SOLAR ACTIVITY
Abstract: China has long and continuous historical records on severe weather dating back four thousand years. Occurrences of severe weather events related to temperature anomalies, precipitation irregularities, and floods during the eight high and low solar activity periods of 1–1825 AD (Anno Domini) are statistically investigated. It is found that extreme cold weather occurs preferentially during periods of low solar activity, while inland and coastal flooding tend to correlate with low and high solar activity periods, respectively. Results demonstrate that severe weather occurs significantly more frequently during low solar activity periods than in high solar activity periods.
S. Mukherjee
Title: INFLUENCE OF SUN ON THE SNOWFALL AND RAINFALL
Abstract: Solar variability affects on the climate of the Earth remains a very active research field. Present work attempts to establish a new hypothesis on Sun-Earth atmospheric interactions and opens a new horizon for more accurate weather prediction research. Sun-Earth environment perturbations including Kp (planetary indices), proton flux and electron flux (E-flux) changes. Sudden changes in these parameters may influence the environment of the earth abruptly. If an E-flux rise is responsible for global warming, then an E-flux lowering may lead to snowfall. Along with these variation in the cosmic rays has also been detected before sudden snowfall and rainfall during a relatively warmer environment. During the low sunspot activity in the extended solar minimum of 2009–2010 sudden drops in E-flux and rise in the cosmic rays has been recorded. Similar observation has also been made during Solar maximum as well as in between period (2004–2005) also. This observation directly contradicts the IPCC findings of continuous rise in the atmospheric temperature of the earth due to global warming. Global awareness has improved on the understanding of the global warming, which is supported by the Space Environment Viewing Network (SEVAN) concept. Within year 2011 it will be possible to monitor the cosmic ray fluctuation by the Cosmic Ray Detector across the world.
S Gupta, Z klimont, Chris Heyes, Vinod Jena
Title: ASSESSMENT OF FACTORS RESPONSIBLE FOR CLIMATE CHANGE AND HUMAN HEALTH
Abstract: Weather and climate play important roles in determining patterns of air quality over multiple scales in time and space. Air quality is strongly dependent on weather and is therefore sensitive to climate change. There is growing recognition that development of optimal control strategies for key pollutants like fine particles now requires assessment of potential future climate conditions and their influence on the attainment of air quality objectives. Climate change induced by anthropogenic warming of the earth's atmosphere is a daunting problem. In addition, other air contaminants of relevance to human health, including smoke from wildfires and airborne pollens and molds, may be influenced by climate change. While further research is needed, climate change coupled with air pollutant exposures may have potentially serious adverse consequences for human health in urban and polluted regions. Climate change producing alterations in: food webs, lipid dynamics, ice and snow melt, and organic carbon cycling could result in increased PMs level in air. In this study, the focus is on the ways in which health-relevant measures of air quality, including particulate matter, and aeroallergens, may be affected by climate variability and change. The small but growing literature focusing on climate impacts on air quality, how these influences may play out in future decades, and the implications for human health is reviewed. In the present study to find out the particulate dust in air, the sampling of particulate matters from different locations were carried out during December, 2006 – February, 2007 in Raipur city, one of the most industrialized parts of India, to characterize the ambient mass concentrations of coarse particulate matter (PM10) and their sources. Techniques i.e. thermal method, proton induced X-ray emission spectrophotometry and ion chromatography was used for monitoring the species i.e. trace elements and water soluble ions, respectively and it is observed that the particulates are accompanied by high fractions trace elements (9.7%) and water soluble ions (15.5%), which play an important role in climate change.
V.K. Jena
Title: STUDIES OF CLIMATE CHANGE ON ECOSYSTEMS AND ITS IMPACT
Abstract: This study compiles and summarizes the existing knowledge about observed and projected impacts of climate change on ecosystem. During the course of this century the resilience of many ecosystems is likely to be exceeded by an unprecedented combination of change in climate and in other global change. Climate is an integral part of ecosystems and organisms have adapted to their regional climate over time. Climate change is a factor that has the potential to alter ecosystems and the many resources and services they provide to each other and to society. Human societies depend on ecosystems for the natural, cultural, spiritual, recreational and aesthetic resources they provide. In various regions across the world, some high-altitude and high-latitude ecosystems have already been affected by changes in climate. Climate change could benefit certain plant or insect species by increasing their ranges. The resulting impacts on ecosystems and humans, however, could be positive or negative depending on whether these species were invasive. Observations of ecosystem impacts are difficult to use in future projections because of the complexities involved in human/nature interactions. The observed changes are compelling examples of how rising temperatures can affect the natural world and raise questions of how vulnerable populations will adapt to direct and indirect effects associated with climate change. If greenhouse gases emissions and other changes continue at or above current rates, this will alter the structure, reduce biodiversity and perturb functioning of most ecosystems, and compromise the services they currently provide.