Analysis of OMI NO2 trends in comparison to regional model forecasts for urban areas of the Pacific Northwest

The AIRPACT regional modeling system employs WRF meteorological forecasts with the CMAQ chemical transport model to produce daily air quality forecasts for the Pacific Northwest. As part of an ongoing evaluation of the modeling system using satellite and other resources, three years of modeled NO2 vertical tropospheric column densities (March 2007 to February 2010) are compared to OMI tropospheric NO2 retrievals for urban areas in the Pacific Northwest. The Dutch (KNMI) OMI averaging kernels are applied to the AIRPACT NO2 results for the entire period. Two-week averages over urban areas are used to compare model and satellite results. Also, a comparison is conducted for weekdays versus weekends. Differences in trends in the modeled NO2 columns are attributed to discrepancies in the economic growth applied to the emission inventory, and are hypothesized to reflect the recent US recession. The analysis also addresses differences in Vehicle Miles Traveled data as used in the inventory and as recently updated from the Federal Highway Administration.