P71  Simulating Daytime Boundary Layer Heights and Mesoscale Flows in Complex Terrain using WRF:  a Case Study for the Virginia Blue Ridge Mountains

Lee, Temple, University of Virgina

The height of the daytime planetary boundary layer (PBL) is an important driver of trace gas variability, both in flat, homogenous terrain and in mountainous terrain.  Topographically-driven mesoscale flows play an additional role in explaining trace gas variability in mountainous terrain.  The interaction between mesoscale flows and PBL height and their relative role in driving trace gas variability over mountainous terrain is poorly understood and requires the use of numerical models.  Many of these models use PBL parameterization schemes developed over flat terrain, but their performance in mountainous terrain has not been widely investigated. 

To this end, we perform sensitivity tests with the Weather Research and Forecast (WRF) model and evaluate three different PBL parameterization schemes:  the Yonsei University scheme, Mellor-Yamada-Janjic scheme, and eddy-diffusivity mass-flux scheme.  We evaluate these parameterization schemes using data obtained during the Education in Complex Terrain Meteorology (EDUCT) field experiment, conducted 6-11 April 2009 in the Virginia Blue Ridge Mountains.  Meteorological and trace gas observations were available at both the mountaintop and valley.  PBL height was estimated using rawinsonde observations from the valley and mountaintop, as well as with a wind profiler and LIDAR deployed at the valley and mountaintop, respectively.  We compare observed PBL heights with the WRF-modeled PBL heights to determine which PBL parameterization scheme provides the best estimate of PBL heights.  We then use the model configuration that best estimates PBL heights to investigate the interplay of mesoscale flows and PBL height on mountaintop trace gas mixing ratios.