Middle atmospheric ozone, nitrogen dioxide, and nitrogen trioxide in 2002–2011: SD-WACCM simulations compared to GOMOS observations
Abstract. Most of our understanding of the atmosphere is based on observations and their comparison with model simulations. In the middle atmosphere studies it is common practice to use an approach, where the model dynamics is at least partly based on temperature and wind fields from an external meteorological model. In this work we test how closely satellite measurements of a few central trace gases agree with this kind of model simulation. We use collocated vertical profiles where each satellite measurement is compared to the closest model data. We compare profiles and distributions of O3, NO2, and NO3 from the Global Ozone Monitoring by Occultation of Stars instrument (GOMOS) on ENVISAT with simulations by the Whole Atmosphere Community Climate Model (WACCM). GOMOS measurements are from nighttime. Our comparisons show that in the stratosphere outside the polar regions differences in ozone between GOMOS and WACCM are small. The correlation of monthly and 5-day time series show very high correlation. In the tropical region in the lower stratosphere WACCM shows consistently larger values than GOMOS. In the polar areas GOMOS measurements show ozone losses that can be connected to the elevated NO2 concentrations from solar storms and strong down draft events from the thermosphere that take place in the winter polar regions. In the mesosphere above the ozone minimum at 0.01 hPa (or 80 km) large differences are found between WACCM and GOMOS. Correlation can still be high, but at the second ozone peak correlation falls strongly and the ozone abundance from WACCM is about 60 % smaller than from GOMOS. Outside the polar areas and in the validity region 25–0.3 hPa GOMOS and WACCM NO2 agree reasonably well and the correlation is reasonably high except in the upper stratosphere in the southern latitudes. In the polar areas, where solar particle precipitation and downward transport from the thermosphere enhance NOX abundance, large differences are found between GOMOS and WACCM NO2. For NO3, we find WACCM values agreeing largely with GOMOS with very high correlation. We show that NO3 values depend very sensitively on temperature. The ratio of O3 to NO3 follows closely to the prediction from the equilibrium chemical theory. Abrupt temperature increases from Sudden Stratospheric Warmings are reflected as sudden enhancements of GOMOS and WACCM NO3 values. NO3 values can therefore be used as a proxy for major stratospheric warmings.