11:00 〜 13:00
[PPS04-P04] Fine vertical structures in the Martian atmosphere retrieved from Mars Global Surveyor radio occultation data
キーワード：火星、大気、電波掩蔽
Mesoscale processes in the Martian atmosphere, such as atmospheric gravity waves, boundary layer convection, nighttime near-surface inversion layers and nocturnal high-altitude clouds, are poorly understood even though they are thought to play important roles in the climate system. Vertical temperature profiles obtained by radio occultation technique have provided valuable information on those processes. Previous studies have been based on radio occultation temperature profiles retrieved by the geometrical optics method, in which the vertical resolution is limited by the Fresnel scale of about 500 m. The Full spectrum Inversion (FSI) (Jensen et al. 2004), one of the radio holographic methods, can achieve higher vertical resolution. FSI has been applied to radio occultation data of Venus to study gravity waves with short vertical wavelengths (Imamura et al. 2018; Mori et al. 2021). Here we apply FSI to the radio occultation data obtained in NASA's Mars Global Surveyor mission (Hinson et al. 1999). We have successfully obtained wavelike structures indicative of gravity waves with vertical scales of as small as 100 m and distinct inversion layers near the surface. A significant wave activity was found from the surface to altitudes of tens of kilometers at nighttime southern high latitudes, where the static stability is high, suggesting generation of mountain waves. A prominent temperature drop near the surface was seen in the polar region even in illuminated conditions. In the presentation we will discuss the origins of such structures.