So March has rolled round already,meaning it's the end of the week at which PM2.5 levels were due to have cleared, but they have not done so yet. Overnight readings were towards the top end of DAQI's Low category, and touching into Moderate. The story had been much the same during daylight hours today.

The MetClim forecasts earlier in the week were calling for much clearer air by this point in time. Indeed their most recent one does too.
I'm interested to know how they produce their forecasts. What factors come into play in terms of how pollution is contained in atmospheric layers, or dispersed, or even cleaned by precipitation?

Seeing the speed at which pollution moves across Europe on those forecasts I realise that pollution forecasting for a particular location depends on climate conditions and pollution sources at least 500 km upwind as well as local pollution sources. It really is a sum of macro conditions combined with increasingly micro effects. The amount of traffic on a busy road may be a significant sources of pollution, but on a given day the pollution from a city 300km away may be a larger factor.

Perth in Australia would be an interesting case study in this regard, being as isolated as it is and yet a major city in its own right.