INFLUENCE OF METEROLOGICAL CONDITIONS ON THE AIR QUALITY

 WEATHER

Weather conditions in Riga are mostly influenced by the Baltic Sea thereby winters are mostly with rather little snow and mildly cold (-15 to -20 ^oC) but summers are wet with average temperatures around 14-19 ^oC (exception is the middle of the summer when the temperature is reaching 25-32 ^oC). The wind is mostly from South and South - West direction -blowing to the Sea.

 SEASONAL, DAILY POLLUTION

There is higher sulphur dioxide pollution in Riga during winters, when central heating network and personal boilers are working. This part of pollution is quite low in summer. In city the main pollutant is traffic, therefore traffic flow daily changes influence pollution very mutually, while seasonal influence is less enounce. On Saturdays and Sundays air pollution in Riga is lower, since many people are going to rest outside of Riga and the traffic flow in the city is decreased. Friday is a specific day, when many peoples are going to countryside or sea-side after work or celebrating the weekend.

Under special weather conditions the air temperature is lower at ground and the wind is slow - a cover of warm air is formed above the city and pollution caused by traffic and stationary sources can not escape. The indicator of such weather is the differential temperature, which is a difference of temperature between two thermometers at different height from the ground level (the temperature at 2 and 8 meters above ground are measured in our case). Such situations are observed in Riga very frequently but mostly in nights during spring and autumn seasons.