Diurnal Cycle of Non-Orographic Gravity Waves' Source Altitudes and Its Impacts: Tests With Mars Planetary Climate Model

Abstract

The transfer of momentum due to non-orographic Gravity Waves (GWs) significantly regulates the Martian middle-upper atmospheric dynamics. Thus, these waves influence the transport of tracers and escape in the thermosphere. However, models assume that the non-orographic GWs are emitted from a constant source level that approximates the averaged Planetary Boundary Layer (PBL). We move on to impose that the emission of the waves follows the top of a real-time evaluated PBL to account for the diurnal cycle of the waves' source altitudes and implement this improvement in the Mars Planetary Climate Model (Mars PCM). In the absence of the PBL during the night, the non-orographic GWs are assumed to be launched at altitudes near the surface following Hinson and Wilson (2023, https://doi.org/10.1016/j.icarus.2022.115420)'s results. Sensitivity tests with the Mars PCM show that non-orographic GWs are built up efficiently during the (polar) night. With the new scheme, the angular momentum in the upper atmosphere is enhanced. Additionally, simulations recover the “cold pockets” in temperature observed by the Mars Climate Sounder at 80–100 km and capture “deep drops” of the atmospheric species recorded by the Neutral Gas and Ion Mass Spectrometer in the polar night.