Effect of Land Cover Boundaries on Warm-Season Precipitation Generation in Northwest Mississippi

Author(s): Dyer, J.

Agricultural production in the Mississippi Delta is critically dependent on precipitation; however, warm-season rainfall patterns within northwest Mississippi show that the Mississippi Delta receives a minimum of precipitation relative to adjacent regions. The reasons for this may be associated with gradients in heat and moisture fluxes along the eastern periphery of the Mississippi Delta arising from sharp changes in land cover. Using high spatial resolution simulations from the Weather Research and Forecasting (WRF) model, atmospheric patterns associated with defined non-frontal warm-season convective precipitation events are analyzed to determine the conditions related to rainfall modification in northwest Mississippi. Results show that decreased latent heat flux over the cultivated Mississippi Delta relative to adjacent forested land leads to an increase in localized lower atmospheric temperature. Combined with low-level moisture advection from the Gulf of Mexico, localized convection along the edge of the temperature gradient leads to precipitation generation and subsequent rainfall. Due to climatologically prevalent westerly flow over the region, this rainfall reaches the surface east of the Mississippi Delta. This defined pattern indicates that there is a potential for inter-basin water transport through atmospheric processes, leading to a decrease in precipitation over the Mississippi Delta due to local land cover characteristics. Future research on the quantification of the depth of water associated with atmospheric transport of moisture is imperative to defining regional water resource patterns in northwest Mississippi.

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