Four-dimensional visualization and analysis of convective rainfall generation along an abrupt land use / land cover boundary in northwest Mississippi

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Thursday, 21 January 2010: 11:15 AM
B216 (GWCC)
Jamie L. Dyer, Mississippi State University, Mississippi State, MS

The lower Mississippi River alluvial valley in southeast Arkansas, northeast Louisiana, and northwest Mississippi (a.k.a., the Mississippi Delta) is characterized by widespread agriculture with few urban areas. Land use is predominantly cultivated cropland with minimal topography; however, the eastern edge of the alluvial valley is defined by a rapid, though small, change in elevation into a heavily forested landscape. This change in land use / land cover has been shown to potentially enhance precipitation through generation of a weak mesoscale convective boundary. This project will define and quantify the causes and influence of the land surface on associated precipitation processes by simulating and analyzing a convective rainfall event that was influenced by regional surface features. Analysis will be conducted using four-dimensional visualization and analytic tools on a high-resolution simulated dataset generated by the Weather Research and Forecasting (WRF) model. Four-dimensional analysis allows for a more rapid and precise evaluation of horizontal and vertical moisture and mass transport by allowing for examination of the entire atmospheric column at once, which is extremely useful when studying precipitation processes and generation. Results show that the strongest uplift coincides with an abrupt low-level moisture boundary, which itself is influenced by a rapid change from sensible to latent heat flux relative to the agricultural and forested areas, respectively. Additionally, intense surface heating over the cultivated landscape appears to destabilize the boundary layer, with precipitation occurring as this air is advected across the land cover boundary and the associated moisture gradient. The most intense precipitation generation during this event occurred in the late afternoon, which agrees with the high diurnal variability of surface temperatures and evapotranspiration over the study area.