7.1 Inconsistencies in the Weather Research and Forecasting (WRF) Model of the Marine Boundary Layer along the coast of California

Wednesday, 13 January 2016: 4:00 PM
Room 342 ( New Orleans Ernest N. Morial Convention Center)
Andrew M. Fisher, University of Kansas, Lawrence, KS; and D. A. Rahn

The late spring to early summer near-surface coastal air flow along the shore of California is typically dominated by a subtropical anticyclone 1000km west of the coastline and a thermal low to the east over the desert southwest. The coastal region is susceptible to various mesoscale flows largely forced by a persistent horizontal pressure gradient inducing a strong low-level equatorward flow. Numerous mesoscale meteorological phenomena have been observed along the coastline that are typically driven by interactions between the persistent northwesterly flow, contained in the marine boundary layer, and the topography along the coastline, which modulate the boundary layer height and low-level wind speed. Topographical influence of the low-level jet along the California coast can induce phenomena such as hydraulic jumps, southerly surges, and Catalina eddies. Due to the numerous aforementioned coastal complexities involved, this study explores the accuracies and deficiencies associated with mesoscale numerical weather prediction. Specifically, the Weather Research and Forecasting (WRF) model is implemented and its performance is largely linked to aircraft measurements and surface buoy data from the National Data Buoy Center (NDBC). Airborne measurements are obtained from the Precision Atmospheric Marine Boundary Layer Experiment (PreAMBLE). The University of Wyoming King Air research aircraft collected fifty hours of data over fifteen flights during May and June 2012 to evaluate the atmospheric dynamics associated with the marine boundary layer primarily near Point Conception and the California Bight region. The high resolution data obtained from PreAMBLE has prompted further investigation to analyze the accuracies and deficiencies of WRF. For example, the strength of synoptic forcing, or the magnitude of the low-level flow, strongly influences the model's response especially downstream of points and capes in the coastline. Thus, it is imperative to understand differences between the WRF model and observations to at least identify conditions where the model output is less reliable and then to ascertain the processes in the model that are likely limiting the forecasts, which may direct future efforts in model development that could improve forecasts for coastal communities along the coast of California.
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