Nicholas Savage

Modelling UK Air Quality for AQMEII2 with the Online Forecast Model AQUM

AQUM is an online air quality modelling system which is used to provide the operational Met Office air quality forecast for the UK. The standard model configuration runs at a resolution of 12 km and covers a domain including the UK and part of Western Europe. The model is routinely verified against near-real-time surface pollutant measurements from the UK Automatic Urban and Rural Network (AURN) to provide a continuous evaluation of model performance. We have developed a new configuration of AQUM to run on the AQMEII (Air Quality Modelling Evaluation International Initiative) Phase 2 European domain at a resolution of 22 km, using the prescribed AQMEII emission datasets. This latter dataset contains wildfire emissions which are not included in the standard AQUM emissions. An initial analysis is conducted to compare the emissions over the UK used as input to both models. Model simulations for 2010 from the AQUM standard and AQMEII configurations are compared to AURN surface observations and an analysis of the effect of the differing model domain, resolution and emissions is made. In 2010 Russian wildfires constituted a significant additional source of pollutants in Eastern Europe; we evaluate the impact of these wildfire emissions on UK air quality.

Evaluation of a Year-Long Ozone Hindcast for 2006 as Part of a DEFRA Model Intercomparison

A variant of the operational forecast configuration of the Met Office’s newly developed Eulerian Air Quality Forecast Model was used to generate an air quality hindcast for 2006 as part of a DEFRA model intercomparison. Verification of predicted ozone concentrations was carried out by comparing against hourly observations from 15 rural and urban background sites spread over the UK. Models were primarily assessed statistically using standard metrics including bias, mean error, correlation, and fraction of predictions within a factor of 2 of observations for (a) all observations, and (b) periods of elevated ozone (>100 μg/m3). We will present results showing that the Met Office model is competitive with other models for hourly ozone, but is best in class at modelling episodes of elevated ozone. The results indicate that the availability of high quality met data and interactive treatment of chemistry and meteorology are both important in modelling ozone episodes.

Forest fire plumes over the North Atlantic: p-TOMCAT model simulations with aircraft and satellite measurements from the ITOP/ICARTT campaign

[1] Intercontinental Transport of Ozone and Precursors (ITOP) (part of International Consortium for Atmospheric Research on Transport and Transformation (ICARTT)) was an intense research effort to measure long-range transport of pollution across the North Atlantic and its impact on O3 production. During the aircraft campaign plumes were encountered containing large concentrations of CO plus other tracers and aerosols from forest fires in Alaska and Canada. A chemical transport model, p-TOMCAT, and new biomass burning emissions inventories are used to study the emissions long-range transport and their impact on the troposphere O3 budget. The fire plume structure is modeled well over long distances until it encounters convection over Europe. The CO values within the simulated plumes closely match aircraft measurements near North America and over the Atlantic and have good agreement with MOPITT CO data. O3 and NOx values were initially too great in the model plumes. However, by including additional vertical mixing of O3 above the fires, and using a lower NO2/CO emission ratio (0.008) for boreal fires, O3 concentrations are reduced closer to aircraft measurements, with NO2 closer to SCIAMACHY data. Too little PAN is produced within the simulated plumes, and our VOC scheme’s simplicity may be another reason for O3 and NOx modeldata discrepancies. In the p-TOMCAT simulations the fire emissions lead to increased tropospheric O3 over North America, the north Atlantic and western Europe from photochemical production and transport. The increased O3 over the Northern Hemisphere in the simulations reaches a peak in July 2004 in the range 2.0 to 6.2 Tg over a baseline of about 150 Tg.