Thermal tides in Martian atmosphere observed by EMIRS onboard the Hope spacecraft

Abstract

<p>Thermal tides are planetary-scale harmonic responses driven by diurnal solar forcing and influenced by planetary topography. Excited by solar heating absorbed by the atmosphere and energy exchange with surface, thermal tides grow in Martian atmosphere. These tides usually have large amplitudes due to the low heat capacity of Martian atmosphere, and dominate its diurnal variations. In this talk, we present results of the analysis of thermal tides in Martian atmosphere using temperature profiles retrieved using infrared spectra obtained by the Emirates Mars InfraRed Spectrometer (EMIRS) instrument onboard the Emirates Mars Mission (EMM) Hope spacecraft. The first set of data obtained during the mission science phase is selected, covering a solar longitude (L<sub>S</sub>) range 60° - 80° of Martian Year (MY) 36, which is a clear season without large dust storms. The novel orbit design of the spacecraft allows a full local time coverage to be reached within 10 Martian days, approximately ~5° of L<sub>S</sub>. It enables the analysis of diurnal temperature variations without the interference of seasonal changes, which was shown to be significant in previous studies. Wave mode decomposition is also applied to these diurnal variations, and amplitudes of other tide modes are derived. The results show good agreements with predictions derived using the Laboratoire de Météorologie Dynamique (LMD) Mars Global Circulation Model (GCM), except for a noticeable phase difference of the dominant diurnal thermal tide. This work provides valuable information on understanding diurnal variations in Martian atmosphere and inspires future advances of Mars GCMs.</p>