Effect of Land-Atmosphere Coupling on Interannual Variability of Central American Climate

We investigate the influence of land-atmosphere coupling on interannual variability of climate in the Central America- Caribbean region. Previous studies using global climate models have found evidence of strong land-atmosphere coupling in parts of this region. Physiographic detail such as complex coastlines and topography have the potential to modify land-atmosphere coupling through regional orographic and thermally driven circulations, but these terrain features are resolved coarsely if at all in global model. As an example, the Gulf of California, which plays an important role in the onset and propagation of the North American monsoon, does not exist in typical GCM land-sea masks. Here we examine the influence of land-atmosphere coupling in more detail by using a regional climate model that can better resolve the complex terrain of Central America. We have used RegCM4 to perform GLACE-type experiments over the CORDEX Central America domain and supplement these with statistical metrics of land-atmosphere coupling. Results using ERA-interim boundary conditions for 1989-2009 show that land-atmosphere coupling has substantial influences on interannual variability of precipitation in the region, with coupling "hot spots" that differ in both location and magnitude from those found using global models. We also find that land-atmosphere coupling appears to be important for regional climatic phenomena such as the North American monsoon.