Representation of the Sierra Barrier Jet in 11 years of a high-resolution dynamical reanalysis downscaling

The Sierra Barrier Jet (SBJ) is a dynamically-generated low-level jet along the windward (i.e., western) slope of the Sierra Nevada of California that influences precipitation distribution and aerosol/water vapor transport in California's Central Valley. Because of its importance to local climate and weather conditions, its representation in numerical models is critical. However, the climatic representation of the SBJ within numerical models is undocumented. This project investigates how well the SBJ is represented in numerical models, primarily documenting its representation within a high-resolution, 11-year WRF reanalysis downscaling. We undertake a comprehensive validation of this dynamical downscaling during 11 cool seasons (water years 2001-2011, Oct.-Mar.) with available wind profiler data at Chico, CA (CCO). Using the SBJ objective identification tool described in Neiman et al. (2010), we identify SBJ cases in the CCO wind profiler data, as well as in the WRF data at the gridpoint nearest this site; WRF's representation of the SBJ is compared with that of other reanalysis products with different horizontal resolutions (e.g., the North American Regional Reanalysis) to assess the spatial resolution necessary to correctly capture this topographically-induced low-level jet. The modeled timing, strength, altitude, and duration of the SBJ at CCO are compared with observations. A catalog of modeled events that have significant timing overlap with the observations is created and used to further assess the model's representation of the winds during SBJ events. In addition, observation-model comparisons of other meteorologically important variables during wintertime storms that impact California (e.g., bright band height at CCO, profiles of winds throughout CA, and Central Valley boundary layer temperature profiles) are performed in order to evaluate WRF's ability to capture the dynamical evolution of the SBJ.