Forecast Methodology

How are the forecasts produced?

The air quality forecasts are provided by the Met Office on a daily basis, 365 days a year, for locations across Sussex. These forecasts are checked, and whenever there is a predicted exceedance of the “moderate” air quality banding, alerts are triggered and sent out to recipients.

The Met Office weather forecast and climate prediction model uses UK and European maps of annual average pollutant emissions to simulate the release of chemical species into the atmosphere. These are then allowed to chemically react according to prescribed reaction rates, which depend on factors including the concentration of the species, the temperature and the amount of sunlight. Species are then transported and dispersed within the model according to the winds, and the concentrations are re-evaluated. Using the concentrations calculated in this way throughout the forecast period, the Daily Air Quality Index is calculated as an average over prescribed time periods. We have found that our Air pollution forecasts can be improved by using recent observations of air quality from across the UK, together with our forecast model, to give an adjusted forecast. We, therefore, use observations from the Automatic Urban and Rural Network (AURN) as part of our forecast system. (Source: https://www.metoffice.gov.uk/weather/guides/air-quality-forecast).

How the Air Quality Bands are Calculated

Band Index Ozone Nitrogen
Dioxide
Sulphur
Dioxide
PM2.5
Particles
PM10
Particles
Running 8
hourly mean
Hourly
mean
15 minute
mean
24 hour
mean
24 hour
mean
µg m-3 µg m-3 µg m-3 µg m-3 µg m-3
Low
  1 0-33 0-67 0-88 0-11 0-16
2 34-66 68-134 89-177 12-23 17-33
3 67-100 135-200 178-266 24-35 34-50
Moderate
  4 101-120 201-267 267-354 36-41 51-58
5 121-140 268-334 355-443 42-47 59-66
6 141-160 335-400 444-532 48-53 67-75
High
  7 161-187 401-467 533-710 54-58 76-83
8 188-213 468-534 711-887 59-64 84-91
9 214-240 535-600 888-1064 65-70 92-100
Very High
  10 241 or more 601 or more 1065 or more 71 or more 101 or more

 

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