GSWM Sample Output: January Meridional Diurnal Tide

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Jan Merid 24hr Tide: Alt v. Lat
Animation cycles three times (three solar days). [ESC] to stop, Reload to replay.

Contour plot of the meridional (northward) diurnal tidal perturbation in January as a function of altitude, latitude, and local time. Dashed lines and blue colors indicate soutward winds. This cross section is independent of longitude. The phase velocity is downward, though the tide propagates upward.

Note the peak between 100-110km and the diminishing amplitude elsewhere (due to the denser atmosphere at lower altitudes, and gravity wave stress at higher altitudes). The tide is not strongly driven near the poles.

The phase of the tide differs by 12 hours across the equator, so the maxima in opposite hemispheres at a given altitude and time occur in the opposite directions.

Contrast with the diurnal zonal tide (April case), which has the same phase across the equator and is therefore more symmetric. Note the strength of this diurnal tide near the equator in a latitude vs. longitude "top view" at 100km (April).

See how the phase difference across the equator of 1/2 of a period persists even in the different structure of the semidiurnal meridional tide (January).