Seasonal variations of orographic clouds on Mars with MRO/MARCI observations and the Mars Planetary Climate Model

Abstract

Although an appreciable amount of research has been conducted studying the Aphelion Cloud Belt (ACB) and Polar Hoods (PHs), much less attention has been given to orographic clouds on Mars. Orographic clouds (afternoon) are generally observed in northern Spring and Summer since they are associated with the significant Martian volcanoes. The water ice optical depths near 15h00 LTST (Local True Solar Times) provided by the Mars Color Imager (MARCI) of Mars Reconnaissance Orbiter (MRO) are used to investigate seasonal and spatial variations of orographic clouds in four volcanic regions: Alba Patera, Olympus Mons, Tharsis region and Elysium Mons. The seasonal variations of water ice clouds over volcanic areas need to be better understood. Thus, context will be provided using the meteorological fields from the Mars PCM (Mars Planetary Climate Model led by the Laboratoire de Météorologie Dynamique Paris, France). This study provides a general picture of how Martian afternoon water ice clouds correlate with Mars PCM’s meteorological variables: water ice column, atmospheric temperature, meteorological winds, and water vapor mixing ratio. Comparison between the model and the MARCI observations show that spatial and seasonal variations of atmospheric temperature, water vapor, and meteorological winds strongly control the water ice cloud distribution during northern hemispheric Spring and Summer.