Impacts of Gravity Waves in the Martian Thermosphere: The Mars Global Ionosphere-Thermosphere Model Coupled With a Whole Atmosphere Gravity Wave Scheme

摘要

Gravity waves are a key mechanism that facilitates coupling between the lower and upper atmosphere of Mars. In order to better understand the mean, large-scale impacts of gravity waves on the thermosphere, a modern whole atmosphere, nonlinear, non-orographic gravity wave parameterization scheme has been incorporated into a three-dimensional ground-to-exosphere Mars general circulation model, the Mars Global Ionosphere-Thermosphere Model (M-GITM). M-GITM simulations utilizing the gravity wave parameterization indicate that significant gravity wave momentum is deposited in the thermosphere, especially within the altitude range of 90-170 km. This impacts the winds in the thermosphere; in particular, M-GITM simulations show a decrease in speed of the wind maximum in the summer hemisphere by over a factor of two. Gravity wave effects also impact the temperatures above 120 km in the model, producing a cooler simulated thermosphere at most latitudes. M-GITM results were also compared to upper atmospheric temperature and wind data sets from the MAVEN (Mars Atmosphere and Volatile Evolution) spacecraft. Some aspects of wind data-model comparisons improved once the gravity wave scheme was added to M-GITM; furthermore, a cooler temperature profile produced by these new M-GITM simulations for the MAVEN Deep Dip 2 observational campaign resulted in a closer data-model comparison, particularly above 180 km. Overall, these modeling results show that gravity waves play an important role for the energy and momentum budget of the Martian thermosphere.