Effects of model resolution on the interpretation of satellite NO2 observations
- ISSN: 16807316
- DOI: 10.5194/acp-11-11647-2011
Inference of NOx emissions (NO+NO2) from satellite observations of\ntropospheric NO2 column requires knowledge of NOx lifetime, usually\nprovided by chemical transport models (CTMs). However, it is known that\nspecies subject to non-linear sources or sinks, such as ozone, are\nsusceptible to biases in coarse-resolution CTMs. Here we compute the\nresolution-dependent bias in predicted NO2 column, a quantity relevant\nto the interpretation of space-based observations. We use 1-D and 2-D\nmodels to illustrate the mechanisms responsible for these biases over a\nrange of NO2 concentrations and model resolutions. We find that\npredicted biases are largest at coarsest model resolutions with negative\nbiases predicted over large sources and positive biases predicted over\nsmall sources. As an example, we use WRF-CHEM to illustrate the\nresolution necessary to predict 10 AM and 1 PM NO2 column to 10 and 25%\naccuracy over three large sources, the Four Corners power plants in NW\nNew Mexico, Los Angeles, and the San Joaquin Valley in California for a\nweek-long simulation in July 2006. We find that resolution in the range\nof 4-12 km is sufficient to accurately model nonlinear effects in the\nNO2 loss rate.