The goal of this investigation is to characterize the spatially and seasonally evolving structure of Martian atmospheric temperature and infer the distributions of radiatively active dust and water ice clouds that are consistent with the observed planetary-scale forced waves. Forced waves include quasi-stationary waves arising from zonal variations in topography, surface properties, and aerosol fields. Also included are the thermal tides, which are the atmospheric response to diurnally varying thermal forcing due to radiative and convective heat transfer from the surface and aerosol heating within the atmosphere. Thermal tides are particularly relevant, as the diurnal variation of temperature is most directly responsive to aerosol radiative forcing. Therefore comparing observed forced wave atmospheric fields derived from spacecraft data with those in climate model simulations provides a means of assessing the ability of current models to replicate important aspects of the Martian climate. An ability to reasonably represent the dependence of diurnally-varying temperature structure to changes in water ice clouds and dust provides confidence that changes to the atmospheric circulation, including the boundary layer climate, can also be represented and studied.
Figure 1 shows an aspect of our study of the effect of a planetary-scale dust storm on atmospheric temperatures. The figure shows the very large increase in the diurnal and semidiurnal range of air temperature following the development of a global dust storm in June of 2018. The March Year 34 dust storm began development around Ls=187° and reached maturity by Ls =200°. The very large increase in the diurnal and semidiurnal tide amplitudes are accompanied by a large increase in zonal and diurnal mean air temperature and large changes in the intensity of the atmospheric circulation at all heights, including the near-surface winds, which play a key role in lifting dust. We are using such modeling, combined with temperature and aerosol observations by the Mars Reconnaissance Orbiter (MRO) Mars Climate Sounder (MCS) to better understand the initiation, growth and decay of global dust storms. We are also investigating how the surface pressure observations by Mars Science Laboratory (MSL) and Viking Lander 1 (VL1) relate to the global scale thermal forcing of the tide.
