How Well Can a Climate Model Simulate the Response of Summer Rainfall in the Southeast United States to Tropical Sea Surface Temperature Anomalies?

We have examined the National Center for Atmospheric Research (NCAR) Community Atmospheric Model Version 3.5 (CAM3.5) to determine how realistic the model can simulate summer rainfall climatology and anomalies in the Southeast United States (SE US) and their relationship with the sea surface temperature anomalies (SSTA) over the adjacent tropical oceans. Our results suggest that the model reasonably well simulates the climatology and the range of the climate variability of the rainfall over US, but cannot capture the years of the interannual drier or wet anomalies and decadal scale change of the precipitation in US. The circulation pattern associated with the interannual dry anomalies over the SE US is similar to that observed although the low-level anticyclonic circulation center bias southward. The teleconnection between the rainfall over the SE US and the SSTA over the Pacific is well captured, but that with the Atlantic SSTA is not by the model. Further analysis suggests that inadequate linkage between SSTA in the Atlantic, the Bermuda High, which influences moisture transport from Gulf of Mexico, and rainfall in the SE US is at least in part responsible for lack of predictability of summer rainfall anomalies in SE US shown in CAM3.5.