Model Output History Files
==========================
.. _historyoutput:
NetCDF History Output Files
---------------------------
TIEGCM history files are output in `netCDF `_,
a self-describing platform-independent data format written and maintained by the UCAR
`Unidata `_ program.
Each netCDF file contains one or more :term:`histories `, i.e., the state of the
model output fields at a discrete instant in :term:`model time`. Here is an example of the
metadata content of a sample primary history file: :download:`primary.ncd <_static/primary.ncd>`.
This example file contains six daily histories (days 355 to 360 of 2002).
This metadata is obtained via the "ncdump" command in the netCDF utilities. This example
ncdump file contains data values for scalar and singly-dimensioned vectors only. You can
also use the tgcm_ncdump script in the :term:`scripts/` directory.
TIEGCM history files are "CF compliant", i.e., they conform to the
`NetCDF Climate and Forecast (CF) Metadata Convention `_.
Primary and Secondary History Files
-----------------------------------
"Primary" history files contain the "prognostic" fields necessary to restart the model.
They can be specified in namelist input as the :ref:`SOURCE ` file for starting
the model in an :term:`initial run` (a :term:`continuation run` does not specify a SOURCE
file, and is continued from the START time found on one of the files in the OUTPUT file list).
Typically, daily histories are stored on primary history files.
Fields on primary histories necessary for start-up of the TIEGCM are as follows:
TN, UN, VN, O2, O1, N4S, NO, HE, AR, OP, N2D, TI, TE, NE, O2P, OMEGA, Z, POTEN
(see the below table). There are also several fields with the suffix "_NM" that
contain data from the previous timestep, necessary for the job-stepping scheme for
prognostic variables. Lower boundary conditions for neutral temperature and winds
are also on the primary history (TLBC, ULBC and VLBC).
"Secondary" history files contain diagnostic fields and/or primary history fields.
Fields to be saved on the secondary history files are listed by the namelist input
parameter :ref:`SECFLDS `. Diagnostics can be saved by calling subroutine addfld
in the code (addfld.F), or by including one or more of the "standard" diagnostic fields
available via the :ref:`diagnostics ` module (diags.F). Secondary histories
are often saved at a higher temporal resolution than primary histories, typically hourly.
Here is an ncdump of an :download:`example secondary history file <_static/secondary.ncd>`
.. _primaryfields:
Table of Primary History Fields
-------------------------------
This is a table of prognostic fields that are saved on primary histories.
These fields are necessary for restarting the model. They can also be saved
on secondary histories by adding the short name to the :ref:`SECFLDS `
field list in the namelist input file. Here is an ncdump of the example
primary file: :download:`primary.ncd <_static/primary.ncd>`.
========== ================================= ==========
Short Name Long Name Units
========== ================================= ==========
TN NEUTRAL TEMPERATURE deg K
UN NEUTRAL ZONAL WIND (+EAST) cm/s
VN NEUTRAL MERIDIONAL WIND (+NORTH) cm/s
O2 MOLECULAR OXYGEN mmr
O1 ATOMIC OXYGEN mmr
N4S N4S mmr
NO NITRIC OXIDE mmr
HE HELIUM mmr
AR ARGON mmr
OP O+ ION mmr
N2D N2D mmr
TI ION TEMPERATURE deg K
TE ELECTRON TEMPERATURE deg K
NE ELECTRON DENSITY cm-3
O2P O2+ ION cm-3
OMEGA VERTICAL MOTION s-1
Z GEOPOTENTIAL HEIGHT cm
POTEN ELECTRIC POTENTIAL volts
========== ================================= ==========
As mentioned above, several of these fields are also required at the previous
model timestep, for the leap-frog time-stepping scheme. These fields have the
suffix '_NM', added to their names, e.g., TN_NM, UN_NM, VN_NM, etc.