[P-PS09] 火星と火星衛星

[PPS09-14] 中緯度移動性擾乱に伴う火星のローカルダストストーム

*小郷原 一智¹ (1.京都産業大学理学部)

キーワード：火星大気、砂嵐、中緯度、傾圧波

Dust storms in western Arcadia Planitia were extracted from visible images obtained by the Mars Orbiter Camera (MOC) onboard the Mars Global Surveyor (MGS) spacecraft using deep learning. Local dust storms in this region were concentrated between roughly the northern autumn and spring equinoxes, except around the northern winter solstice. In addition, transient eddies with wavenumber 3 in the lower atmosphere tended to be amplified when the local dust storms were frequent. The atmospheric environment around this area when the dust storms were observed was investigated via a composite analysis of the Mars reanalysis dataset, and it was found that local dust storms tended to be observed near the southern edge of a warm and southerly wind anomaly associated with a transient eddy with wavenumber 3. Because the MGS observations are limited to around 14:00 local time, there is a 1-sol uncertainty in the timing of dust storm onsets. Using backward trajectory analysis, we estimated the location and time of each dust storm onset in the 24 Martian hours prior to the time when the dust storm was observed. The results still show that the observed dust storms tend to occur in and around the warm and southerly wind anomaly. This warm inflow from the south into the extratropical cyclone made the lower atmosphere less stable convectively during the day and enhanced the southerly wind on the northern slope of Elysium Mons during the night to induce the formation of the meso-scale dust storms.