How to read an air quality forecast
Read a CAMS forecast by model, valid time and location. Learn what changes between runs and why a city forecast differs from a roadside reading.
A forecast describes a model grid cell
Air quality models use weather, estimates of emissions and atmospheric chemistry to estimate how pollutants will move or change. PiSpace Air uses Copernicus Atmosphere Monitoring Service (CAMS) forecasts through Open-Meteo. The regional European product describes a finer grid than the global product, which covers a wider area.
Open-Meteo documents about 11 km grid spacing and hourly values for the European forecast, compared with about 45 km and three-hourly native output for the global forecast. An hourly display can include values estimated between native model steps. Nearby cities can be represented by the same cell.
Run time and valid time
The run time identifies when the model started a prediction, when that timestamp is supplied. The valid time identifies the hour the value describes. A new run can change the estimated concentration for the same future hour. The time PiSpace fetched a response is a separate timestamp.
Look at the full range and the times with higher or lower values. A predicted change shows what the model estimates. Its timing can shift in a later run as weather and emissions inputs change.
Forecasts, estimates and observations
A forecast valid for the current hour can be shown as a model estimate. A station may report a different concentration in the same hour because it samples a specific environment, such as a street or park. PiSpace labels the data type on both the overview and chart.
The forecast and observation panels can become available at different times. If a run expires or a value is missing, the affected panel shows a gap or an unavailable state.