Impact of AIRS Thermodynamic Profiles on Precipitation Forecasts for Atmospheric River Cases Affecting the Western United States

Atmospheric rivers are transient, narrow regions in the atmosphere responsible for the transport of large amounts of water vapor. These phenomena can have a large impact on precipitation. In particular, they can be responsible for intense rain events on the western coast of North America during the winter season. This paper focuses on attempts to improve analyses of heavy precipitation events in the Western US due to atmospheric rivers. While assimilation of radiances from the Atmospheric Infrared Sounder (AIRS) occurs in regional forecast models, these observations are only assimilated in clear regions, which means that atmospheric rivers may not be adequately sampled. Temperature and water vapor profiles from AIRS are retrieved in partly cloudy regions and may provide enhanced analyses of moisture associated with atmospheric rivers. These observations are combined with GFS analyses using the three-dimensional variational Gridpoint Statistical Interpolation (GSI) data assimilation system to produce an AIRS-enhanced analysis product. Verification of these AIRS-enhanced analyses will be done using special observations obtained during the Winter Storms and Pacific Atmospheric Rivers (WISPAR) field campaign as well as through gridded verification of precipitation forecasts from the Weather Research and Forecasting (WRF) for 3 test cases in the winter of 2011. These analyses and forecasts will be compared to GFS analyses and forecasts to demonstrate the impact of the AIRS profiles Results will be presented showing the impact of the AIRS profile data on water vapor and temperature fields, and on the resultant precipitation forecasts.