Potential Biosphere Response to Climate Change and its Impact on Regional Climate Prediction over West Africa

We present preliminary results from ongoing 21-year long simulations over West Africa with a regional climate model (RegCM3) asynchronously coupled to a dynamic vegetation model (CLM-DGVM). Three experiments are performed in order to explore the climatic impact of vegetation feedback. In a "Control" experiment, RegCM3 is first run for a year using CCSM3 present day boundary conditions, vegetation distribution (vegetation type and LAI) consistent with the CCSM present day climatology from a prior CLM- DGVM integration, CCSM present day Sea Surface Temperature (SST) monthly data, and atmospheric CO2 concentration fixed at the present day value of 356ppm. The resulting climate from the RegCM3 is used to force CLM-DGVM for a restart simulation which is one year long. The new vegetation distribution from CLM- DGVM is then used for the second year of RegCM3 run. The iteration continues for the entire 21-year RegCM3 simulation. In a "Future" experiment, lateral and surface boundary conditions are based on CCSM3 future SRESA1B output, with CO2 concentration fixed at 720ppm. The third experiment is similar to the "Future" experiment, but with vegetation distribution maintained at the present day state. The results illustrate the importance of including vegetation feedback in regional climate predictions.