Diurnal temperature variations and migrating thermal tides in the Martian lower atmosphere observed by the Emirates Mars InfraRed Spectrometer

TL;DR

This study uses Emirates Mars InfraRed Spectrometer data to analyze diurnal temperature variations and thermal tides in the Martian atmosphere, revealing seasonal and latitudinal patterns and comparing results with climate models.

Contribution

First comprehensive analysis of Martian diurnal temperature variations and thermal tides using high-altitude orbit observations from EMM.

Findings

Dominant diurnal tide observed in most seasons.

Semi-diurnal tide amplitude peaks near perihelion.

Seasonal variation of tides explained by zonal wind vorticity.

Abstract

The Martian atmosphere experiences large diurnal variations due to the ~24.6 h planetary rotation and its low heat capacity. Understanding such variations on a planetary scale is limited due to the lack of observations, which are greatly addressed with the recent advent of the Emirates Mars Mission (EMM). As a result of its unique high-altitude orbit, instruments onboard are capable of obtaining a full geographic and local time coverage of the Martian atmosphere every 9-10 Martian days, approximately ~5{\deg} in solar longitude (LS). This enables investigations of the diurnal variation of the current climate on Mars on a planetary scale without significant local time (LT) gaps or confusions from correlated seasonal variations. Here, we present the results of diurnal temperature variations and thermal tides in the Martian atmosphere using temperature profiles retrieved from the Emirates Mars InfraRed Spectrometer (EMIRS) observations. The data during the primary mission is included, covering an entire Martian Year (MY) starting from MY 36 LS = 49{\deg}. The diurnal temperature patterns suggest a dominant diurnal tide in most seasons, while the semi-diurnal tide presents a similar amplitude near perihelion. The seasonal variation of the diurnal tide latitudinal distribution is well explained by the total vorticity due to zonal wind, while that of the semi-diurnal tide following both dust and water ice clouds, and the ter-diurnal tide following the dust only. Comparison with the updated Mars Planetary Climate Model (PCM, version 6) suggest improvements in simulating the dust and water cycles, as well as their radiative processes.