Mars Climate Sounder (MCS) on Mars Reconnaisance Orbiter (MRO) collected limb observations for most of the 2007 global dust storm event. MCS is a nine channel infrared radiometer with limb staring arrays optimized of atmospheric sounding. In the 15 micron channel (nominally designed for pressure and high altitude temperature retrievals), the lowest detector (pointed 5 km below the surface) has a nadir like weighting function peaking around 30 km. Daily day and night maps of the brightness temperature in this channel reveal the thermal characteristics of the dust storm evolution.As expected, the overall trend is for the atmosphere to warm as the dust storm evolves and then slowly cool as the dust settles out. But there are a number of very interesting patterns. By comparing the day side and the night side maps, it is possible to distinguish between heating due to local dust and dynamically driven heating due to the circulation. The northern extra polar dynamical heating at the beginning of the dust storm occurs almost as soon as the dust heating is detected. Apart from the active dust heating, the southern polar region is the warmest overall with the tropics being cooler than anywhere except in the northern polar vortex. The evolution of the northern polar vortex is quite complex, the core warms up significantly during the storm. Given the temperatures jump from being in the CO2 condensation range to well above it at 30 km for a long period, it will be interesting to see if there are significant differences in the defrosting cycle next spring. Despite the warmer polar air during the storm, the dynamically heated air outside the vortex forms a very steep latitudinal gradient which is often sharper than before the start of the storm, potentially implying some very strong thermal gradient winds.
AAS/Division for Planetary Sciences Meeting Abstracts #39
- Pub Date:
- October 2007