Air Quality Catalogue

Set up of the NCAS Air Quality Forecasting System

The NCAS Air Quality Forecast (AQF) system is aimed at the scientific community interested in the prediction of air quality related pollutant species over the UK. DEFRA operate the official air quality forecast system for public information.

The NCAS AQF system, which is is operated by the Centre of Atmospheric and Instrumentation Research, University of Hertfordshire, employs an integrated modelling framework for producing operational air quality forecasts based on WRF-CMAQ. Daily forecasts of up to three days are performed for Europe and UK domains at a grid resolution of 50km and 10km respectively (shown in the figure below).

AQF forecasting domain
Fig. The forecasting domain. The outer domain at 50km resolution covers Europe while the inner domain at 10km resolution covers the UK.

The outer domain, also known as mother domain, provides the lateral boundary conditions to the nested UK domain. There are a total of 24 vertical levels up to 10 hPa. The grid is stretched along the vertical axis to accommodate a high resolution within the boundary layer (9 layers up to about 2000 m above ground-level) and close to the ground surface. Digital elevation, soil type, land cover data, and the other characteristics of the soil and the ground surface (e.g. monthly surface albedo) are derived from the default geographical data that is provided with the WRF pre-processing system.

Meteorological initial (ICs) and lateral boundary conditions (BCs) of the outer domain are derived from the National Centers for Environmental Prediction (NCEP) FNL (Final) Operational Global Analysis data available every six hours. Chemical boundary conditions are from MACC II (Monitoring Atmospheric Composition and Climate) global forecast. The TNO emission inventory is processed with the Sparse Matrix Operator Kernel Emissions system adapted at CAIR for UK and European domains. Biogenic emissions are generated with the Model of Emissions of Gases and Aerosols from Nature (MEGAN) and CB05 chemical mechanism is used with a tri-modal approach to aerosol size distribution to model particulate matter.

For further information on the NCAS Air Quality Forecasts please contact Professor Ranjeet S Sokhi, Centre of Atmospheric and Instrumentation Research, University of Hertfordshire.