Tropospheric NO2 columns over Northeastern North America: Comparison of CMAQ model simulations with GOME satellite measurements

We present comparisons of the NO2 regional Chemical Transport Model (CTM) simulations over Northeastern North America during the time period from May to September, 1998 with hourly surface NO2 observations and the NO2 columns retrieved from the COME (Global Ozone Monitoring Experiment) satellite instrument. The model calculations were performed using the Mesoscale Meteorological Model 5 (MM5), Sparse Matrix Operator Kernal Emissions (SMOKE), and Community Multiscale Air Quality (CMAQ) modeling systems, using the emission data from the National Emissions Inventory (NEI) databases of 1996 (U.S.) and 1995 (Canada). The major objectives were to assess the performance of the CMAQ model and the accuracy of the emissions inventories as they affected the simulations of this important short-lived atmospheric species. The modeled (N-CMAQ) and measured (N-GOME) NO2 column amounts, as well as their temporal variations, agreed reasonably well. The absolute differences (N-CMAQ-N-GoME) across the domain were between +/- 3.0 x 10(15) Molecules cm(-2), but they were less than +/- 1.0 x 10(15) molecules cm(-2) over the majority (80%) of the domain studied. The overall correlation coefficient between the measurements and the simulations was 0.75. The differences were mainly ascribed to a combination of inaccurate emission data for the CTM and the uncertainties in the GOME retrievals. Of these, the former were the more easily identifiable.