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.