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Dawson, Jon
(2014).
DOI: https://doi.org/10.21954/ou.ro.0000f112
Abstract
A spectral GCM for Mars was converted to Venus parameters (radius, gravity, rotation rate), and tested to determine the optimum configuration for use as a Venus Global Circulation Model.
Super-rotation, a circulation of the atmosphere faster than the underlying planet, is a particular feature of the of Venus’ atmosphere where the wind speed at the cloud tops is ~100 ms-1. It is important that the model developed can reproduce this feature.
A reference simulation was performed at T21 resolution and forced with a realistic temperature profile, super-rotation was achieved of ~50 ms-1 with strong meridional circulation. Topography was added and found to make little difference to the superrotation, the meridional circulation was stronger than the reference with counter cells developing above the high elevation features. Tests were performed with increased background temperature profiles, and therefore stability, used for the forcing. It was found that peak zonal winds increased and the meridional circulation weakened as the stability increased. Realistic wind speeds could be achieved by tuning the temperature increase. A simple diurnal cycle was introduced and the results presented when run with a maximum temperature increase of 100 K over the reference simulation temperature profile.
The sensitivity of the model to vertical and horizontal resolution was tested. It was found at that 50 vertical levels provided the best compromise between good results and the computer time required. The final value of global super-rotation and the time taken for the simulation to reach equilibrium were found to be strongly dependent on the horizontal resolution. T42 resolution reaching equilibrium faster than the lower resolutions tested thus offsetting the additional computer time required.
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