1College of Chemistry, University of California Berkeley, Berkeley, CA 94720, USA
2Department of Earth and Planetary Sciences, University of California Berkeley, Berkeley, CA 94720, USA
*now at: Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964, USA
**now at: Sonoma Technology, Inc., Petaluma, CA 94954, USA
Abstract. We examine spatial variations in the weekday–weekend pattern of NO2 over the Los Angeles metropolitan area using the Ozone Monitoring Instrument (OMI) and then compare the observations to calculations using the WRF-Chem model. We find that the spatial pattern of the weekday–weekend variations of the NO2 column in the model is significantly different than observed. A sensitivity study shows that the contrasting spatial pattern of NO2 on weekdays and weekends is a useful diagnostic of emissions and chemistry. These improvements suggest that constraints from space-based observations of the processes affecting urban photochemistry (e.g., spatial patterns of emissions, ratios of VOC to NOx emissions, rate constants) are possible at a level of detail not previously described.