Lately, together with the numerical weather forecast, in many European countries Systems for Chemical Weather Forecast operate, Chemical Weather being understood as concentration distribution of some key pollutants in a particular area and its changes during some forecast period.

In Bulgarian Chemical Weather Forecast System (BgCWFS) the forecast period is 3 days starting at 00 UTC each day and the forecast regions are 5: Europe, Balkan Peninsula, Bulgaria, Sofia Region and Sofia City. The nesting approach is used increasing the space resolution from 81 km (Europe) to 1 km (Sofia City).

The System is fully atomized. It is based on the well known models WRF (Mesometeorological Model) and USEPA dispersion model CMAQ (Chemical Transport Model). As emission input the TNO data is used for the two biggest domains. For the 3 Bulgarian domains the current emission inventory prepared by Bulgarian environmental authorities is exploited.

The System is realized in two versions::

• BgCWFSv2.1 (Europe - Balkan Peninsula - Bulgaria) and
• BgCWFSv2.2 (Bulgaria - Sofia Region - Sofia City)

In the left side of the pages, a list with 4 key pollutants is displayed: Nitrogen dioxide (NO₂), Sulphur dioxide (SO₂), Ozone (O₃) and Particle Matter with diameters d<10 μm (PM10). Additionally, two kinds of Ozone maximums, required by the European Ozone Directive are presented. The pollutant can be chosen by clicking over the respective link.

In the middle of the page, the concentration distribution of the chosen pollutant for particular region and hour is shown. The hour is chosen by putting the mouse cursor over any point of the point column at the right side of the image. Putting the cursor over “Play” invokes animation in time. Below the image, the respective critical levels for the chosen pollutant according Bulgarian legislation are presented.

In the right side of the page, the forecast domains are indicated. A click on any one of them loads the respective images.