The effects of clouds on transient baroclinic eddies in a Mars General Circulation Model

• Main Author: Rucker, Michael S.
• Other Authors: Barnes, Jeffrey R., Hutchings, Jennifer K., Suryan, Robert M., Skyllingstad, Eric D., College of Earth, Ocean, and Atmospheric Sciences, Oregon State University. Graduate School
• Format: Master Thesis
• Language: English; unknown
• Published: Oregon State University
• Subjects: Mars (Planet) > Atmosphere > Mathematical models; Atmospheric circulation > Mars (Planet) > Mathematical models; Baroclinicity; Clouds > Mars (Planet) > Dynamics; Mars (Planet) > Dust storms; Mars (Planet) > Meteorology > Mathematical models; Ice cap
• Online Access: https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/5712m9574

The low-level baroclinic eddy activity seen in the NASA Ames Mars General Circulation Model (MGCM) for simulations under three annual dust cycles are characterized. Simulations were conducted with both radiatively active and radiatively inert clouds (RAC and non-RAC, respectively) for 11 continuous annual cycles for each dust case. Model results for the 11th year were analyzed. These results show the crucial importance of RAC for simulating transient baroclinic eddies in the lower atmosphere of Mars. Total temperature variance with RAC is greater by about a factor of two above the non-RAC cases. RAC effects modify the meridional location of the eddy activity shifting them to latitudes more in line with the seasonal CO₂ ice cap, and in most seasons, RAC effects act to broaden the vertical structure of the eddies. The non-RAC cases show eddy activity much too poleward and shallow, especially in the northern hemisphere. In the RAC cases, strong eddy activity is seen in the MGCM during northern springtime, which over time, closely tracks the retreating CO₂ ice cap. Interestingly, this activity is not observed by MGS TES, however, this may be due to instrument limitations as these eddies appear very shallow during this season in the MGCM. Perhaps most importantly, RAC effects shift the distribution of eddy activity in zonal wavenumber. RAC effects change the periodicity and amplitude of temperature variance for zonal wavenumber 1, 2 & 3, especially in the north as compared to the non-RAC cases. Zonal wavenumber 3 temperature variance with RAC is increased by a factor of ∼4-5. In select seasons, RAC effects can produce zonal wavenumber 3 as the dominant mode, in temperature variance, whereas it is never the dominant mode in the non-RAC cases.