Soil-wind erosion is a severe problem that degrades air quality and visibility in the Pacific Northwest. Air quality is a large scale issue, requiring a regional air quality model to simulate/forecast agricultural dust emission, dispersion and transport as affected by environmental conditions and farm practices. The USDA-ARS Wind Erosion Prediction System (WEPS) is a process-based model that has the ability to simulate dust emission from agricultural soils at a field scale, but WEPS lacks a capability to model dust dispersion and regional transport. However, for dust effects on regional air quality, WEPS needs to be incorporated into a regional scale models, such as found in the EPA Community Multi-scale Air Quality (CMAQ) model with the Sparse Matrix Operator Kernel Emissions (SMOKE) modeling system. The hybrid model is called WEPS-AIRPACT3.
The domain of WEPS-AIRPACT3 contains Washington, Oregon, Idaho, and part of North California, Nevada, Utah, Wyoming, and Montana. The WEPS-AIRPACT3 requires development of soil and landuse databases across the entire domain. The soil database was developed based upon NRCS-STATSGO soil database. In STATSGO, one polygon corresponds to 21 components along with 1-60 properties, one component also contains 6 layers which include 1-28 properties. The one-to-many relationships was reduced to one-to-one relationships in our database through summarizing component percentage weighted average. Depth of same layer of different components of each map unit was standardized to 10 cm for the first horizon and 20 cm for each of the remaining horizons. The established 8 state databases contain 30 soil properties which were aggregated and calculated for 10 normalized layers. The EPA Biogenic Emissions Landcover Database version 3 (BELD3) provides percentages of USGS classified land cover and 230 vegetation classes at resolution of 1 km. Both the soil and landcover databases were gridded into either 1 or 12 km cells across the entire domain.