Representation of the Sierra Barrier Jet in 11 years of a high‐resolution dynamical reanalysis downscaling compared with long‐term wind profiler observations

Abstract

We investigate the representation of the Sierra Barrier Jet (SBJ) in four numerical models at different resolutions, primarily documenting its representation within a high‐resolution (6 km), 11‐year WRF reanalysis downscaling (WRF‐RD). A comprehensive validation of this dynamical downscaling is undertaken during 11 cool seasons (water years 2001–2011, October to March) using available wind profiler data at Chico, CA (CCO). We identify SBJ cases in the observed CCO wind profiler data, as well as in WRF‐RD at the closest grid point. WRF‐RD's representation of the SBJ at CCO is compared with that of other reanalysis products with coarser horizontal resolutions (i.e., the North American Regional Reanalysis (NARR), the California Reanalysis downscaling, and the NCEP/NCAR Reanalysis) to assess whether downscaling is necessary to correctly capture this topographically induced low‐level jet. Detailed comparisons across California between WRF‐RD and NARR suggest downscaling is necessary: Only WRF‐RD at 6 km resolution is well‐capturing this dynamical feature. A catalog of modeled SBJ events that have significant timing overlap with observations is created and used to further assess WRF‐RD's representation of SBJ events. In addition, observation‐model comparisons of other meteorologically important variables (e.g., precipitation melting level, wind profiles, temperature, and relative humidity) are performed in order to evaluate WRF‐RD's ability to capture the dynamical evolution of the SBJ. The detailed, case‐by‐case comparisons reveal WRF‐RD accurately represents 56 percent of the 256 observed SBJ cases occurring during these 11 cool seasons, albeit with a weak wind bias that increases with jet maximum wind strength.