How does weather affect air pollution?
Prevailing weather conditions can weaken or improve air quality. Strong winds can rapidly transport pollutants hundreds of kilometres, whereas during weak wind circumstances, pollutants can accumulate around the source of the release. The rain can either clean or pollute the environment depending on harmful substances in the air.
Weather conditions have a major impact on air quality. If the weather conditions change, also the prevailing air quality situation can change very quickly. In Finland, the common air quality problems vary depending on the different seasons.
Wind impacts the transport of air pollution. In urban environments, the mixing of traffic emissions can be very poor during weak wind circumstances but also strong winds can provide rapid transport of air pollution to distant locations. For example, long range transported particles can contain pollution from industry and power production as well as pollution from wildfires or controlled agricultural burning.
Street dust during springtime is a recurring problem in Finland because sand and grit are used to reduce the slippery conditions of streets during wintertime. Especially studded tires increase the amount of road dust in the air in urban areas. Fog and rain effectively clean the air locally.
Especially during summertime, photochemical reactions are very powerful in sunny and warm weather. For example, surface ozone can form on warm, sunny days than on cold, cloudy days.
Sometimes weather situations change rapidly and naturally these changes reflect on the measured air pollution concentrations. For validating concentration observations and for understanding the origin of the pollutants, it is needed to study simultaneously.
the weather during observation
routes of polluted air flows
circumstances during transportation
source of release
Air quality in Finland
Serious air quality episodes are relatively rare in Finland, because cities are smaller and geographically scattered. Also, traffic is not as heavy in Finland compared to other parts of Europe. In Finland, high air pollution concentration values are measured usually for a shorter time and in smaller areas compared to other European countries. Although the air quality in Finland is generally very good, concentrations of pollutants can occasionally rise to harmful levels in unfavourable weather circumstances.
Authorities' role in air pollution control
Local authorities in municipalities or cities monitor the local air quality and inform the public if necessary. The responsibilities are stated in the National Environmental Protection Act. Local authorities in municipalities have a responsibility to arrange air quality monitoring needed in local circumstances and maintain air quality measurement stations in Finland. Local environmental authorities measure air quality in ca. 50 places across the country. Finnish Meteorological Institute (FMI) measures air quality in the rural background stations which are located outside cities, far away from emission sources. Also operators of different industrial activities have a responsibility to be aware of the impacts of their activities on air quality.
Air quality observations around Finland
All authorities and organisations who measure air quality in Finland can send their observations to be published in real time on the air quality website maintained by FMI. Air quality observations have been described with an easy-to-understand colour scale. Finnish air quality index is used to describe the prevailing air quality situation. In addition to the air quality observations, rain and wind observations can be chosen on the same map. Rain or wind can weaken or improve air quality. The current air quality situation, and the past 24 hours with 1 hour intervals can be viewed on FMI's website.
FMI's activities
FMI supports preparedness of municipalities with scheduled plans by offering localized forecasts of conditions favourable for AQ episodes to its customers. The air quality forecasts are based on the meteorological situation and describe the potential risk of weather conditions causing poor air quality or when poor air quality will improve. In addition to forecasts, there are many different air quality research fields in FMI, e.g. air quality assessments in urban and industrial areas and air quality laboratory services.
