Large Uncertainty in Future Projections of Southwestern United States Precipitation through the 21st Century

Abstract:

Southwestern United States (SW US; 29-40 N, 235-255 E) 21st century precipitation projections have a large uncertainty across 43 models of the Coupled Modeled Intercomparison Project phase 5 (CMIP5) Representative Concentration Pathway 4.5 (RCP4.5), with some models projecting wetting and others projecting drying. They show a projected precipitation range for 2100 of -10.18% to +18.33% relative to Global Precipitation Climatology Project version 2.2 (GPCP 2.2) precipitation climatology. One model, the Community Atmosphere Model version 5 (CAM5), illustrates a robust drying trend for 2100 of -6.98% to -0.86% relative to GPCP 2.2 precipitation climatology. CAM5 simulations show most drying is related to future anthropogenic aerosol decreases. Future work will investigate reasons for the large uncertainty in CMIP5 future projections, which is likely related to large natural variability. We will also analyze mechanisms by which future anthropogenic aerosol decreases may contribute to 21st century SW US drying.