Mars Mesoscale Modeling Capability Development, 15-9363

Principal Investigator
Scot C. R. Rafkin

Inclusive Dates: 12/01/02 - 12/01/03

Background - The Mars Regional Atmospheric Modeling System (MRAMS) is the most advanced mesoscale numerical model of Mars' atmosphere. The primary objective of this proposal is to maintain and strengthen this position by implementing a new water, carbon dioxide, and dust aerosol bin microphysical parameterization that is coupled to a size and species dependent radiative transfer scheme. A second objective is to apply the updated model to a new class of problems that are difficult or impossible to address without coupled microphysics and radiation packages, e.g, initiation and maintenance of regional dust storms, development of orographic clouds, and dust and water transport in the convective boundary layer.

Approach - To accurately model the formation and evolution of water and carbon dioxide ice clouds in the Martian atmosphere, a modified version of the CARAMA microphysical model will be coupled to MRAMS. This model is a time-dependent microphysical cloud model that incorporates the processes of nucleation, condensation, evaporation, and sedimentation of water and carbon dioxide, including homogeneous processes, and heterogeneous processes involving dust nuclei. The microphysics are parameterized via a bin model to approximate a continuous size distribution.

Radiative transfer code to calculate the effect of hydrometeors (dust and cloud) on atmospheric heating rates in the solar and infrared wavelengths will also be implemented. The radiative transfer model employs the correlated-k method to calculate the gaseous optical depths for carbon dioxide and water vapor in 60 wavelength bands ranging from 440 to 40,000 cm^-1. A stratified Mie code is used to calculate the optical depths for both cloud and dust particles. These opacities are utilized by a two-stream code to calculate the total solar and infrared fluxes and heating rates at each altitude interval.

Modeling of realistic cloud and dust phenomena with MRAMS will be conducted. Initial modeling targets will be Olympus Mons, Elysium Mons, and the Tharsis highlands as a whole. As time allows, additional modeling targets will be selected. Model solutions will be compared and verified (to the fullest extent practically possible) with Mars Orbiter Camera images, temperature data from the Thermal Emission Spectrometer instrument, data from the radioscience team, and possibly Mars Orbiter Laser Altimeter cloud returns.

Accomplishments - This project is still in progress. To date, the microphysical code has been implemented and tested. The radiation code has been implemented and is currently undergoing tests. The results from the model are quite promising.

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