Past and future simulations of NO2 from a coupled chemistry-climate model in comparison with observations
Other literature type
Trends in derived from a 45 year integration of a chemistry-climate
model (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 N<sub>2</sub>O, the primary source gas for
stratospheric NO<sub>2</sub>. This suggests that the processes driving the trend are
not solely dictated by changes in but are coupled to global atmospheric
change, either chemically or dynamically or both. If CCMs are
to accurately estimate future changes in ozone, it is important that they
comprehensively include all processes affecting NO<sub>x</sub> (NO+NO<sub>2</sub>)
because NO<sub>x</sub> concentrations are an important factor affecting ozone
concentrations. Comparison of measured and modelled NO<sub>2</sub> trends is a
sensitive test of the degree to which these processes are incorporated in
the CCM used here. At Lauder the 1980-2000
CCM NO<sub>2</sub> trends (4.2% per decade at
sunrise, 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 not
significantly different at the 2σ level.
Large variability in both the model and measurement data from Arrival
Heights makes trend analysis of the data difficult.
CCM predictions (2001-2019) of NO<sub>2</sub> at Lauder and Arrival Heights show
significant reductions in the rate of increase of NO<sub>2</sub> compared with
the previous 20 years (1980-2000).
The model results indicate that the
partitioning of oxides of nitrogen changes with time and is
influenced by both chemical forcing and circulation changes.