In this article we look at our air quality forecasting, which is now publicly available on our website in time for the Games.
Whether you're an Olympic or Paralympic athlete breathing hard in pursuit of a gold medal or a member of the public going about your daily routine, air quality can be important to our lives.
No matter where we are, the air we breathe contains small amounts of trace gases and particles which can affect everything from performance during exercise to our general health.
Weather plays a big part in determining air quality and the Met Office is now providing 'Daily Air Quality Index' forecasts out to five days for more than 5000 locations across the UK. These include Olympic and Paralympic venues, such as the Olympic Park, locations along the Olympic Marathon route and Eton Dorney, potentially providing valuable information to competing athletes and spectators alike.
Two of the most important parts of an air quality forecast are knowledge of the emission of pollutants into the atmosphere, for example from industrial processes or vehicle fumes, and an understanding of what the weather is doing.
Sunlight can promote reactions between pollutants already in the air to give rise to secondary pollutants, such as ozone. Calm winds can allow pollutants to build up and stronger winds can disperse pollution; rain can remove it from the atmosphere.
These links between the weather and air quality mean the Met Office is well placed to provide air quality forecasts.
Our weather forecasting model has been developed to include many of the key processes which can affect air quality, such as the transport and dispersion of pollutants by the wind, the removal of pollution by rain, and the chemical reactions between gases and aerosols in the atmosphere.
Dr Paul Agnew from the Air Quality and Composition team at the Met Office said: "Our model simulates the release of pollutants into the atmosphere and looks at how these will react, depending on factors including how concentrated they are, temperature and the amount of sunlight.
"The model then tracks how these will be transported and dispersed in the atmosphere according to wind, or how they will be washed out by rain, to give a forecast for air quality over specific areas."
From this we produce a five-day forecast of air quality, using the Daily Air Quality Index (DAQI) scale set out by Defra, where 1 is the best air quality and 10 the worst. The DAQI is accompanied by health advice both for people who are at risk in poor air quality conditions (such as those with lung, heart conditions, asthma and older people), as well as the general population.
The advice from Defra states: "Here in the UK, air pollution does not rise to levels where people need to make major changes to their lives - nobody need fear going outdoors, but in times of poor air quality forecasts can help people minimise exposure. When levels of air pollution increase it would be sensible for those who are particularly affected to limit their exposure to air pollutants by reducing exertion outdoors.
"Some athletes, even if they are not asthmatic, may notice they find their performance less good than expected when levels of a certain air pollutant are high and they may notice they find deep breathing causes some discomfort in the chest. This does not mean that they are in danger, but it would be sensible for them to limit their activities on such days if possible."
The Met Office checks the accuracy of air quality forecasts by comparing to air quality observations from the Automatic Urban and Rural Network maintained by Defra for monitoring air quality in the UK. In this way we can monitor how well our forecasts perform.
Dr Agnew points out that the Met Office air quality forecasts represent the regional or 'background' air quality away from strong sources of pollution such as busy roads, and that air quality may be significantly poorer close to these areas. More information is available on the science background to our forecasts.
Daily air quality index forecasts are available for each of over 5000 location forecasts on the Met Office website along with information and advice on what the forecast means.
During the London 2012 Olympic and Paralympic Games you can also find more detailed Air Quality forecasts on the Met Office science showcase web pages.
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25 July - 12 August - Check the five day weather forecast for the London 2012 Olympic Games.