The Advanced Research version of the Weather Research and Forecasting (WRF) model, known as WRF-ARW, is used to simulate a couple of high-concentration periods during the 2007-2008 winter season in the Fairbanks region. The meteorological output from the WRF-ARW simulations will be used to drive the Community Multiscale Air Quality (CMAQ) model. The baseline meteorological model configuration uses three nested model domains of 12-km, 4-km, and 1.333 km horizontal grid spacing (a finer 444-m grid is also included in some simulations), and 7 layers in the lowest 50 m above ground level with vertical grid spacing of only 4 m near the surface.
A multi-scale four-dimensional data assimilation (FDDA) procedure, newly developed for the WRF-ARW model, is used to provide the lateral boundary conditions for the finer-resolution domains used to study the physical interactions associated with these stable layers. Sensitivity tests are performed to determine the added value of various model physics parameterizations and options (e.g., land surface models, boundary layer parameterizations, and moist microphysics) for predicting these high-latitude stable boundary layers. The model results are subjectively and objectively evaluated against available quality-controlled observations. The best combination of mesoscale data assimilation methods and model physics for predicting these very stable boundary layers, so important for modeling air quality in these very cold environments, will be discussed.