Explainer

Air Quality: How does the weather impact air pollution?

Different types of weather affect the amount of pollution in the air.The main problems are caused by sunshine, temperatures, wind and pressure. Rain, on the other hand, can improve air quality.

Sunshine:

Sunshine can cause some pollutants to undergo chemical reactions, resulting in smog. On hot sunny days the pollution from vehicles reacts to form a pollutant called ozone. This is often created in cities and towns where there is traffic but because this pollution can be transported by winds, high levels of ozone may be found in the countryside. 

Temperature:

Higher temperatures can speed up these chemical reactions in the air.But it’s also worth noting that colder temperatures in winter result in more people using their cars, idling engines to keep warm and increased burning of fires which all create pollution.

Wind:

The wind can move pollutants around - this can be good if it disperses them but also a problem as it moves pollution to other areas such as the countryside. And even from one continent to another.

Finding Saharan dust on your car or windows is a good example of the distance pollutants can travel on the winds. Winds may relieve pollution over one area but simply create a new problem elsewhere.

Pressure: 

Under areas of high pressure where there are often low or no winds the still conditions can allow poor air to build up and linger. This will be more likely in the winter when air can become very stagnated under an area of high pressure. And, of course, in winter we are more likely to burn fossil fuels and use our cars.

Rain: 

Rain, thankfully, usually results in less air pollution since it can dissolve and wash away some pollutants. When we have lower pressure in the atmosphere it is more often wet and windy and this disperses the pollution.

The Great Smog of 1952:

This was a result of severe pollution and weather. Normally smoke would rise into the air. But high pressure at the time pushed the air down and so when the smoke left the chimneys it was trapped along with gases and particles and other pollution from the continent. These toxic conditions led to the deaths of around 4000 people.

We can still get a build up of harmful smog in the UK but thankfully not on this scale anymore due legislation and improvements in technology.

Heat Waves:

Heatwaves can lead to poor air quality and be a real problem for public health. The extreme heat and stagnant air increases the amount of pollution in the air.

In certain countries it also increases the chances of drought and wildfires - and the fires can add huge amounts of pollution to the atmosphere. Smoke from the Australian bush fires in 2019/20 caused more than 10 times the number of human deaths than the fire itself.

The weather can therefore be used to help put together the Daily Air Quality Index, and help forecast pollution levels

Air Quality Index Example Credit: ITV Weather - with data from DEFRA and Met Office

 It uses a colour coded scale of 1 to 10.

Low air pollution is between 1 and 3, Moderate between 4 and 6, High is between 7 and 9, and Very High is 10 on the scale 

Air pollution levels Credit: ITV Weather, DEFRA and Met Office
  • 1-3: Enjoy your usual outdoor activities

  • 4-6: At risk individuals consider reducing physical activity outdoors

  • 7-9: Anyone experiencing discomfort should reduce physical activity

  • 10: Everyone should avoid or reduce physical activity

You can find more information on air quality on the CleanAirHub