This project led by Dr. Mark Richardson will provide new insight into the processes that control the Martian dust cycle, including the development of global dust storms. A General Circulation Model (GCM), originally developed to study the Earth's climate, and subsequently adapted for Martian application, will be used to study the global dynamics of dust lifting and transport. Data obtained from multiple years of observations by the Viking Orbiters and the Mars Global Surveyor Orbiter will be used to constrain model simulations to realistic states. The model will treat dust injection by small-scale convective motions (such as dust devils) and model-resolved wind stresses. Dust is transported within the atmosphere by resolved winds and by diffusion, representing unresolved motions. Gravity is allowed to act on the dust particles, generating dust settling back onto the surface. While in the atmosphere, dust modifies the visible and thermal infrared optical depths, modifying atmospheric heating rates and hence the circulation. The system is thus highly coupled and non-linear. The model is to be used to study the processes that maintain the ubiquitous, but seasonally varying background distribution of dust in the Martian atmosphere. It is currently not known how important dust devils and convective motions are, on a global basis. A major goal of this project is the generation of quazi-variable, spontaneous global dust storms, which have never previously been simulated in a GCM. These studies will focus on the mechanisms of storm generation and interannual variability of the storms. It is anticipated that this study will result in the first simulation of the Martian dust cycle to generate both the seasonal variation of haze and quazi-variable global dust storms using a completely unprescribed, prognostic dust scheme. More importantly, exploration of the behavior of the model should yield insight into the processes operating in the dust cycle that have hitherto not been accessible to quantitative study. These insights will have implications for our understanding of the maintenance of the Martian climate, and how this climate may have varied over the course of Martian geological history.
The activities associated with this project will have a major impact on the education and training of the graduate student and post-doctoral scholar involved. The major tool to be used in this study, the GCM, provides a useful means for training students in the numerical simulation of the atmosphere and climate system. Development of this tool provides a continuing facility for other projects and further research/training opportunities in the future. Smaller projects spurring-off from this activity will provide foci for undergraduate research opportunities, through Caltech's Summer Undergraduate Research Foundation (SURF) program, which the PI has been involved in during each summer since his appointment at Caltech. ***
