High Resolution Projections of 21st Century Daily Precipitation for the Contiguous USA

Abstract:

Changes in precipitation have the potential to produce a wide range of impacts across human and natural systems. Precipitation projections from AOGCMs participating in Phase 5 of the Coupled Model Intercomparison Project (CMIP5) are downscaled to a high resolution (0.25°× 0.25°) grid covering the contiguous USA and used to derive multiple descriptors of 21^st century precipitation climate. Projections for the Northeast, Pacific Northwest and the high elevations of the Rocky Mountains are characterized by increases in total annual precipitation, with the magnitude of the increase highly dependent on the level of radiative forcing. Parts of the southern USA are projected to experience moderate precipitation decreases under all forcing scenarios. Increases in total annual precipitation are associated primarily with changes in cold season precipitation and with the precipitation intensity process. Significant precipitation decreases are projected for parts of the southern USA in all seasons except autumn and are associated primarily with the precipitation occurrence process. Many locations in the eastern USA are projected to experience longer extreme dry spells and longer extreme wet spells, reflecting an increase in the serial correlation of precipitation. Many western locations, on the other hand, are projected to experience shorter dry spells and wet spells, reflecting a decrease in the serial correlation of precipitation. Most US locations are projected to experience an increase in extreme precipitation, reflected in increases in the mean annual single-day maximum precipitation and the number of heavy (>10mm) and very heavy (>20mm) precipitation days.