An Analysis of the Evolution of Physical Processes Producing Daily Widespread Precipitation Extremes in Alaska using six CMIP5 GCMs

• Main Author: Rickhoff, William
• Format: Text
• Language: unknown
• Published: Iowa State University Digital Repository 2016
• Subjects: Meteorology; Arctic; Gulf of Alaska; Aleutian Island; permafrost; Alaska
• Online Access: https://lib.dr.iastate.edu/mteor_stheses/5; https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1013&context=mteor_stheses

The Arctic climate system is warming faster than in any other part of the world due to anthropogenic processes. Products of a warming climate, such as thawing permafrost, flooding, and increases in precipitation can have a negative impact on the Arctic region. In this study, we compared contemporary and future climates over Alaska using six Global Climate Models (GCMs) from the Coupled Model Intercomparison Project (CMIP5) in order to analyze the evolution of physical processes that produce widespread extreme precipitation events in December, January, and February (DJF). We defined a widespread extreme precipitation event as those at or above the 99.9th percentile of all events and covering 11 or more 1o x 1o grid boxes simultaneously. We compared the contemporary composites to the future composites to understand how the atmospheric conditions associated with widespread extreme precipitation events evolve with a changing climate. The circulation patterns of the future climate remained similar to that of the contemporary climate, with a trough stationed over the region and a low pressure located over the Aleutian Island area. Temperature increased from the contemporary climate to future climate, causing the 500-hPa heights, saturation vapor pressure, and specific humidity to increase as well. Moist air from the Gulf of Alaska is advected into the area and topographically forced up the coastal mountain ranges, providing the necessary lift for widespread extreme precipitation events. This topographical forcing, combined with an increase in moisture, results in higher-intensity widespread extreme precipitation events in the future.