Modeling analysis of springtime transition of NO2, CO and O3 on the basis of satellite measurements

GOME measurements of NO2, MOPITT measurements of CO and tropospheric O3 derived from TOMS and SAGE measurements over North America in spring (February to May 2000) are analyzed using a regional chemical transport model (RCTM). The model simulates well the observed NO2 and CO columns. The contributions by photochemistry, lightning NOX emission, and convective transport to the observed seasonal changes of NO2 and CO columns are analyzed. The agreement between measurement-derived and simulated O3 columns is not as good even though both show an increasing trend. We use ozonesonde measurements during this period from 6 stations (35N to 53N) to investigate further the reasons for the discrepancies between satellite-measurement derived and simulated tropospheric O3 columns.