The influence of synoptic weather regimes on UK air quality: regional model studies of tropospheric column NO<sub>2</sub>
Synoptic meteorology can have a significant influence on UK air quality. Cyclonic conditions lead to the dispersion of air pollutants away from source regions, while anticyclonic conditions lead to their accumulation over source regions. Meteorology also modifies atmospheric chemistry processes such...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2015-10-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/15/11201/2015/acp-15-11201-2015.pdf |
| Summary: | Synoptic meteorology can have a significant influence on UK air quality.
Cyclonic conditions lead to the dispersion of air pollutants away from source
regions, while anticyclonic conditions lead to their accumulation over source
regions. Meteorology also modifies atmospheric chemistry processes such as
photolysis and wet deposition. Previous studies have shown a relationship
between observed satellite tropospheric column NO<sub>2</sub> and synoptic
meteorology in different seasons. Here, we test whether the UK Met Office Air
Quality in the Unified Model (AQUM) can reproduce these observations and then
use the model to explore the relative importance of various factors. We show
that AQUM successfully captures the observed relationships when sampled
under the Lamb weather types, an objective classification of midday UK
circulation patterns. By using a range of idealized NO<sub><i>x</i></sub>-like tracers
with different e-folding lifetimes, we show that under different synoptic
regimes the NO<sub>2</sub> lifetime in AQUM is approximately 6 h in summer and
12 h in winter. The longer lifetime can explain why synoptic spatial tropospheric column
NO<sub>2</sub> variations are more significant in winter compared to summer, due to
less NO<sub>2</sub> photochemical loss. We also show that cyclonic conditions have
more seasonality in tropospheric column NO<sub>2</sub> than anticyclonic conditions as they
result in more extreme spatial departures from the wintertime seasonal
average. Within a season (summer or winter) under different synoptic regimes,
a large proportion of the spatial pattern in the UK tropospheric column NO<sub>2</sub> field can
be explained by the idealized model tracers, showing that transport is an
important factor in governing the variability of UK air quality on seasonal
synoptic timescales. |
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| ISSN: | 1680-7316 1680-7324 |