The Effects of Sea Surface Temperatures on North American Monsoon Rainfall in 2003

Sea surface temperature (SST) is recognized as important to atmospheric circulation from decadal to seasonal scales. In this research, the effects of SSTs on rainfall from weekly to monthly are numerically tested using mesoscale model NCAR/PENN MM5 during North American monsoon (NAM) season in year of 2003. For emphasis of the relative importance on SSTs, different types of SSTs are employed as sensitivity tests. These SSTs include Reynolds 1o by 1o weekly SST, FNL 1o by 1o skin temperature, and Aqua SSTs that include mid-infrared (IR) channels and thermal IR channels retrieved SSTs. The preliminary results show that, when high-resolution MODIS SST was used, the precipitation was much improved, especially over tropical oceans and western Mexico costal. Over the US inland, precipitation was also changed when SST changed. The effect of SST on precipitation lags 3-4 days over costal area and 5-7 days over inland. It could be concluded that SST is important to weakly, monthly scales in mesoscale model.