Land Use Land Cover Change Effects on Southern Great Plains Precipitation Patterns

Great Plains land use has changed substantially over the last 160 years, altering both the surface and the soil beneath through increased settlement and advances in irrigation.  Changing the interface between the land and atmosphere has implications for the atmospheric boundary layer, the regional circulation, the local surface energy budget and the resulting precipitation patterns.   Land use land cover (LULC) changes are an important topic for this region due to its heavy dependence on agriculture.  This study investigates differences in Southern Great Plains precipitation patterns between four LULC scenarios; the pre-settlement, 1920’s, Dust Bowl and present day eras.  Using the Weather Research and Forecasting (WRF) model coupled to the Community Land Model (CLM), simulations for each LULC scenario were run for a 12-year period (1990-2002), as this period encompasses a wide variety of remote forcing conditions.  The positive soil moisture - precipitation feedback suggests that the evolution of soil moisture among the four scenarios is crucial to the LULC change effects on Southern Great Plains precipitation.  This study will investigate this feedback mechanism to determine its importance in the region.  In addition, preliminary results revealed a dramatic increase in temperature in far West Texas in the present day scenario in comparison with the previous three scenarios.  This area coincides with a LULC change from barren soil to shrubland.  It is hypothesized that this change in the LULC can alter the wind field with anomalously northerly winds through the development of a thermal low in far West Texas, disrupting the southerly flow of moisture from the Gulf of Mexico, thus reducing accumulated precipitation.