PNNL

Abstract

Persistent midwinter cold air pools produce multi-day periods of cold, dreary weather in valleys and basins. Persistent stable statification leads to the buildup of pollutants and moisture in the pool. Because the pool sometimes has temperatures below freezing while the air above is warmer, freezing precipitation often occurs with consequent effects on transportation and safety. Forecasting the buildup and breakdown of these cold pools is difficult because the physical mechanisms leading to their formation, maintenance, and destruction have received little study. This paper provides a succinct meteorological definition of a cold pool, develops a climatology of Columbia Basin cold pools, and analyzes remote and in situ temperature and wind sounding data for two winter cold pool episodes that were accompanied by fog and stratus, illustrating many of the physical mechanisms affecting cold pool evolution.