Understanding CMIP5 Projected Drying over Meso-America and the Intra-America Seas
We examine the CMIP5 results for a variety of scenarios (RCP85, RCP45, and RCP26) to determine if the same drying signal is present, and to further understand forcing factors. In RCP85 and RCP45, precipitation decreases in spring and early summer and increases in fall, indicating a shift and intensification of the annual cycle. These precipitation changes reflect overall decreases in subtropical precipitation, but regional circulation features such as an early westward expansion of the North Atlantic subtropical high in late spring and a stronger Caribbean LLJ associated with a stronger inter-basin pressure gradient regionally enhance drying. Upper-level circulation changes suggest the same baroclinic response to reduced SST warming in the tropical North Atlantic as in CMIP3. In contrast to RCP85 and RCP45, precipitation increases in the low emissions scenario (RCP26), so projected precipitation changes differ not only in intensity with scenario but also in sign.