6A.1 Evaluation of a combined local and non-local closure PBL model in both WRF and CMAQ simulations compared to observed vertical profiles of meteorological and chemical species

Tuesday, 10 June 2008: 10:30 AM
Aula Magna Vänster (Aula Magna)
Jonathan E. Pleim, EPA, Research Triangle Park, NC; and R. Gilliam and S. Yu

Realistic Planetary Boundary Layer (PBL) simulation of both meteorological parameters and trace chemical species are critical components of combined meteorology and air quality model systems. Ideally, all chemical and meteorological parameters should be modeled using identical PBL modeling techniques. However, air quality models (AQMs) often use PBL schemes that are different from the PBL scheme used in the meteorology model. There are two types of PBL models commonly used in meteorology models, TKE schemes and simple non-local schemes. TKE schemes can be applied to AQMs by using their eddy diffusivities in a local eddy diffusion solver for the subgrid transport of chemical species concentrations. In practice, however, this method usually provides insufficient vertical mixing in daytime boundary layers resulting in over predicted ground level chemical concentrations. While the non-local schemes (MRF, YSU, etc.) generally produce deeper and more well mixed convective boundary layers, the non-local term must be specifically derived for each parameter. It is not clear how the non-local term could be specified for chemical species concentrations. The ACM2, however, is a combined local and transilient scheme, where any quantity can be similarly modeled. Because of its non-local component, the ACM2 produces very similar results for sensible heat as non-local gradient adjustment schemes. However, unlike the gradient adjustment schemes, the transilient transport of the ACM2 is equally effective on any transported parameter. To evaluate how well the ACM2 simulates the PBL structure of both meteorology and chemistry, WRF and CMAQ simulations, both using ACM2, are compared to a variety of observed vertical profiles of both meteorological and chemical parameters from the TexAQS/GoMACCS study including rawinsondes, ozonesondes, radar profilers, both ship borne and aircraft lidar, and aircraft profiles.
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