Cloud trains associated with Martian Mountain Lee Waves on the eastern side of the Phlegra Montes

Abstract

AbstractMountain lee waves have often been observed on the eastern side of the Phlegra Montes as wave trains visualized by water ice clouds in the Martian atmosphere. The seasonality and formation condition of these lee waves and associated cloud trains have not yet been investigated, whereas those of Martian dust storms have been studied observationally and numerically. We extract the cloud trains in this region from images observed by the Mars Orbiter Camera onboard the Mars Global Surveyor and measure the wavelengths of the lee waves. It is revealed that, on the eastern side of the Phlegra Montes, cloud trains tend to form in the northern winter season, except during the 2001 global dust storm. The results suggest that stationary mountain waves are excited in the thermally stable atmosphere, but are trapped below an altitude of approximately 10 km due to the zonal wind structure that increases rapidly with altitude. This is consistent with the previous studies on gravity waves in the Martian atmosphere and is the first study to constrain the typical altitude of the cloud trains from imager observations. Graphical Abstract