A comparison of CCSM4 high-resolution and low-resolution predictions for south Florida and southeast United States drought

It is important to have confidence in seasonal climate predictions of precipitation, particularly related to drought, as implications can be far-reaching and costlythis is particularly true for Florida. Precipitation can vary on fine spatial resolutions, and high-resolution coupled models may be needed to correctly represent precipitation variability. We study south Florida and southeast United States drought in Community Climate System version 4 low resolution (1 degrees atmosphere/ocean) and high-resolution (0.5 degrees atmosphere/0.1 degrees ocean) predictions for time means ranging from 3 to 36months. The very high-resolution in the ocean is of interest here given the potential importance of Gulf Stream on south Florida rainfall. Skill of shorter time-mean South Florida predictions (i.e. 3- and 12-months) are not impacted by increased resolution, but skill of 36-month mean south Florida precipitation is somewhat increased in the high resolution predictions. Notably, over the broader southeast United States the high-resolution model has higher skill for the 36-month mean rainfall predictions, associated with an improved relationship with tropical Pacific and Gulf Stream SSTA. Why this improvement in the broader southeast United States does not extend to Florida is an open question, but does suggest that even further resolution refinements may be needed.