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| Titel |
Air quality modelling using the Met Office Unified Model (AQUM OS24-26): model description and initial evaluation |
| VerfasserIn |
N. H. Savage, P. Agnew, L. S. Davis, C. Ordóñez, R. Thorpe, C. E. Johnson, F. M. O'Connor, M. Dalvi |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1991-959X
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| Digitales Dokument |
URL |
| Erschienen |
In: Geoscientific Model Development ; 6, no. 2 ; Nr. 6, no. 2 (2013-03-12), S.353-372 |
| Datensatznummer |
250017796
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| Publikation (Nr.) |
 copernicus.org/gmd-6-353-2013.pdf |
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| Zusammenfassung |
| The on-line air quality model AQUM (Air Quality in the Unified Model) is a
limited-area forecast configuration of the Met Office Unified Model which
uses the UKCA (UK Chemistry and Aerosols) sub-model. AQUM has been developed
with two aims: as an operational system to deliver regional air quality
forecasts and as a modelling system to conduct air quality studies to inform
policy decisions on emissions controls. This paper presents a description of
the model and the methods used to evaluate the performance of the forecast
system against the automated UK surface network of air quality monitors.
Results are presented of evaluation studies conducted for a year-long period
of operational forecast trials and several past cases of poor air quality
episodes. The results demonstrate that AQUM tends to over-predict ozone
(~8 μg m−3 mean bias for the year-long forecast),
but has a good level of responsiveness to elevated ozone episode conditions
– a characteristic which is essential for forecasting poor air quality
episodes. AQUM is shown to have a negative bias for PM10, while for
PM2.5 the negative bias is much smaller in magnitude. An analysis of
speciated PM2.5 data during an episode of elevated particulate matter
(PM) suggests that the PM bias occurs mainly in the coarse component. The
sensitivity of model predictions to lateral boundary conditions (LBCs) has
been assessed by using LBCs from two different global reanalyses and by
comparing the standard, single-nested configuration with a configuration
having an intermediate European nest. We conclude that, even with a much
larger regional domain, the LBCs remain an important source of model error
for relatively long-lived pollutants such as ozone. To place the model
performance in context we compare AQUM ozone forecasts with those of another
forecasting system, the MACC (Monitoring Atmospheric Composition and Climate) ensemble, for a 5-month period. An analysis of
the variation of model skill with forecast lead time is presented and the
insights this provides to the relative sources of error in air quality
modelling are discussed. |
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