WRF Simulations of the 2009 Southeastern U.S. Convective Season Onset in a Future-Climate Scenario

This work uses the Weather Research and Forecasting model to project how precipitation patterns may change under a warmer climate in the Southeast United States (SE US). Two simulations are performed using boundary conditions from the 6-hourly 0.5 degree Global Forecasting System (GFS) reanalysis data and daily 0.5 degree Real-Time Global Sea Surface Temperature High Resolution data. The first simulation, used as a control in this experiment, models weather in the SE US from March – June in 2009, and is used to represent the seasonal current climate in the region. The second simulation is performed using a pseudo-global warming method assuming an RCP8.5 future climate scenario, using Coupled Model Intercomparison Project Phase 5 multi-model mean temperature anomalies to adjust GFS reanalysis temperature variable values, to model a warmer climate estimated as the 2090 – 2100 decade. Changes in precipitation organization in the warmer climate will be analyzed within a framework which separates precipitation features into two classifications, isolated and mesoscale, depending on whether the precipitation feature is greater or less than 100 km in contiguous horizontal length. This analysis will identify if there are changes in the convective season onset date, and/or in precipitation patterns according to precipitation classification, as well as identify mechanisms that influence precipitation pattern changes in the SE US.