Analysing some martian atmospheric characteristics associated with a dust storm over the Lunae Planum region during October 2014

摘要

This study analyses the vertical aerosol distribution and associated atmospheric characteristics during a dust storm event in early Martian southern summer. The analysis is based on the observations of the Mars Colour Camera (MCC) onboard the Indian Mars Orbiter Mission during October 11 and October 20, 2014. A local-scale dust storm is found within the north-eastern portion of the Lunae Planum region on October 11, 2014, which is observed to be relatively larger during October 20. The dust storm disappeared in the next image taken over the same region during October 28, 2014, leaving a thick haze over Lunae Planum and the Valles Marineris region. It is observed from the Mars Daily Global Maps of the Mars Color Imager (MARCI) on board the Mars Reconnaissance Orbiter (MRO) that the dust storm was generated in the Acidalia region, moved south and came over Lunae Planum and Tempe Terra. Later on, this northern hemispheric storm sequence crossed the equator and merged with a Hellas sequence over Noachis Terra. An increase in vertically integrated dust opacity derived from the observations of Mars Climate Sounder on board MRO was seen over a large latitudinal extent i.e., 60 degrees S to 60 degrees N. Analysis of dust and water ice opacity and temperature profile is carried out before, during and after the dust storm period as observed by MCC and MARCI images. Dust opacity is found to have increased drastically up to 20 km altitude. An increase of dustiness at the HATDM (High Altitude Tropical Dust Maximum) layer is seen, but with a temporal delay of 2 degrees L-s after the dust storm disappearance. The study implicates the variation of convective boundary layer growth in the tenuous Martian atmosphere during the dust storm scenario for this temporal delay in dust lifting. The dust lifting is found to be exclusively responsible for the increase in heating rate at this layer, not cloud radiative heating caused by water ice clouds.