Data assimilation of OMI NO₂ observations for improving air quality forecast over Europe - Research report No. 6884, March 2008

This paper concerns the improvements of NO₂ forecast due to satellite data assimilation. The Ozone Monitoring Instrument (OMI) aboard NASA Aura satellite provides observations of NO₂ columns for air quality study. These satellite observations are assimilated, with the optimal-interpolation method, in an air quality model from Polyphemus, in order to improve NO₂ forecasts in Europe. Good consistency is seen in the comparisons of model simulations, satellite data and ground observations before assimilation. The model results with and without assimilation are then compared with ground observations for evaluating the assimilation effects. It is found that in winter the errors between model data and ground observations have been reduced after assimilation, indicating a better NO₂ forecast can be obtained using satellite observations. Such improvements are not found in summer, which is probably due to the shorter life time and higher temporal variability of NO₂ in the warmer season. (authors)