Identification and Characterization of Cold Pool Events during WFIP2

Cold pool events occur when deep layers of stable, cold air remain for multiple days, and do not get mixed out with daytime heating. Cold pools are important for air quality, freezing events, and especially for wind energy in many locations, and are poorly forecast by modern mesoscale weather prediction (NWP) models. The second Wind Forecast Improvement Project (WFIP2) took place in the Columbia River Basin of Oregon and Washington states from Fall 2015 until Spring 2017, with an extensive field campaign of over 100 instruments and a model development component, aimed at improving short-term wind energy forecasts. Included in the instrumentation were 4 microwave radiometer profilers (MWRP), and 8 wind profiling radars (WPR) with Radio-Acoustic Sounding Systems (RASS) spread across the region, which together provided vertical profiles of temperature, humidity, and wind speed for the duration of the project. Using a basic definition of a cold pool as being a period during which the near-surface atmosphere is colder than aloft and wind speeds are calm for a duration of more than 18 hours, all cold pool events in the region were identified by the MWRPs, WPRs and RASS over two winters. Characteristics of the events, such as duration, depth, and intensity, were identified. Using both routine weather observations and the WFIP2 observations, as well standard analysis products, the large-scale forcing was analyzed, and physical processes were identified that have an impact on the formation and destruction of cold pools in the Columbia River Basin. A better understanding of these processes will hopefully lead to improved physical parameterizations used in the NWP models and improve forecasts of cold pool events.