HR: 0800h
AN: P11A-0248    [Abstracts]
TI: The Influence of Water Ice Clouds on Martian Tropical Thermal Structure
AU: * Wilson, R J
EM: John.Wilson@noaa.gov
AF: NOAA/Geophysical Fluid Dynamics Laboratory, P. O. Box 308, Princeton, NJ 08542, United States
AU: Lewis, S R
EM: S.R.Lewis@open.ac.uk
AF: The Open University, Walton Hall, Milton Keynes, MK7 6AA, United Kingdom
AU: Montabone, L
EM: L.Montabone@open.ac.uk
AF: The Open University, Walton Hall, Milton Keynes, MK7 6AA, United Kingdom
AU: Smith, M D
EM: Michael.D.Smith@nasa.gov
AF: NASA/Goddard Space Flight Center, Bldg 2, Rm S101, Code 693, Greenbelt, MD 20771, United States
AB: The Reanalysis derived from the UK Mars general circulation model (MGCM) assimilation of TES temperature retrievals provides the best current estimate of the evolving state of the martian atmosphere over the course of the Mars Global Surveyor (MGS) mapping mission. The assimilation uses the observed dust column opacity with a vertical distribution that is prescribed as a function of season and latitude. The TES temperature retrievals effectively serve as an external forcing that acts to supplement the model's radiative and dynamical forcing. A Control simulation has also been carried out using the same evolving dust distribution as the Reanalysis, but without the assimilation of temperature. Differences in zonal mean temperatures between these two simulations reflect biases in the representation of dynamical and radiative effects in the MGCM. Model bias is due to missing or incomplete physical processes, as well as errors in the specification of the vertical distribution and radiative properties of aerosols. We have identified a cold bias in the "Control" simulation of the tropical temperature that robustly develops in the northern hemisphere (NH) summer solstice season that we attribute to the absence of radiatively active water ice clouds in the model. We show that MGCM simulations with radiatively active clouds are able to account for the temperature bias in the Control simulation. An analysis of the thermal tides in the Reanalysis is also consistent with this interpretation. We conclude that cloud influences likely play a prominent role in shaping the vertical thermal structure of the tropical atmosphere during the NH summer season
DE: 5210 Planetary atmospheres, clouds, and hazes (0343)
DE: 5405 Atmospheres (0343, 1060)
DE: 5445 Meteorology (3346)
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting