Past and future simulations of NO2 from a coupled chemistry-climate model in comparison with observations

[摘要] Trends in derived from a 45 year integration of a chemistry-climatemodel (CCM) run have been compared with ground-based measurements at Lauder(45° S) and Arrival Heights (78° S). Observed trends in at both sites exceed the modelled trends in N₂O, the primary source gas forstratospheric NO₂. This suggests that the processes driving the trend arenot solely dictated by changes in but are coupled to global atmosphericchange, either chemically or dynamically or both. If CCMs areto accurately estimate future changes in ozone, it is important that theycomprehensively include all processes affecting NO_x (NO+NO₂)because NO_x concentrations are an important factor affecting ozoneconcentrations. Comparison of measured and modelled NO₂ trends is asensitive test of the degree to which these processes are incorporated inthe CCM used here. At Lauder the 1980-2000CCM NO₂ trends (4.2% per decade atsunrise, 3.8% per decade at sunset) are lower than the observed trends(6.5% per decade at sunrise, 6.0% per decade at sunset) but notsignificantly different at the 2σ level.Large variability in both the model and measurement data from ArrivalHeights makes trend analysis of the data difficult.CCM predictions (2001-2019) of NO₂ at Lauder and Arrival Heights showsignificant reductions in the rate of increase of NO₂ compared withthe previous 20 years (1980-2000).The model results indicate that thepartitioning of oxides of nitrogen changes with time and isinfluenced by both chemical forcing and circulation changes.

[学科分类] 大气科学