Projections of Large-Scale Atmospheric Circulation Patterns and Associated Temperature and Precipitation Over the Pacific Northwest Using CMIP6 Models

Climate model projections of 500 hPa geopotential height (Z500) patterns, their frequency, and associated temperature and precipitation anomalies under a high-end global warming scenario are assessed for the Pacific Northwest of North America for the end of the 21st century. Simulations are from models contributing to the 6th phase of the Coupled Model Intercomparison Project (CMIP6) and Z500 patterns are identified using the self-organizing maps approach. Models project a general reduction in the magnitude of Z500 anomalies in summer. The largest temperature increases in winter are found for patterns historically associated with anomalously cold weather and in northern latitudes, while the largest temperature increases in summer are found in inland areas of the Pacific Northwest. Precipitation is found to generally increase across all seasons and patterns, however some historically wet summer patterns are projected to become significantly drier. Significant changes in pattern frequencies are found in summer, with a general decrease in frequency of highly amplified Z500 anomaly patterns.