Meteorological Factors Affecting Air Pollution

Meteorological Factors Affecting Air Pollution

1. Wind speed and direction

2. Temperature

3. Humidity

4. Rainfall

5. Solar radiation.

Wind speed and direction

When high pollutant concentrations occur at a monitoring station, wind data records can determine the general direction and area of the emissions. Identifying the sources means planning to reduce the impacts on air quality can take place.

An instrument called an anemometer measures wind speed. At our monitoring stations, the type of anemometer we use is a sonic anemometer.

Temperature

Measuring temperature supports air quality assessment, air quality modelling and forecasting activities.

Temperature and sunlight (solar radiation) play an important role in the chemical reactions that occur in the atmosphere to form photo-chemical smog from other pollutants.

Favorable conditions can lead to increased concentrations of smog.

The most common way of measuring temperature is to use a material with a resistance that changes with temperature, such as platinum wire. A sensor measures this change and converts it into a temperature reading.

Humidity

Like temperature and solar radiation, water vapour plays a vital role in many thermal and photo-chemical reactions in the atmosphere. As water molecules are small and highly polar, they can bind strongly to many substances. If attached to particles suspended in the air they can significantly increase the amount of light scattered by the particles (measuring visibility). If the water molecules attach to corrosive gases, such as sulphur dioxide, the gas will dissolve in the water and form an acid solution that can damage health and property.

Rainfall

Rain has a 'scavenging' effect when it washes particulate matter out of the atmosphere and dissolves gaseous pollutants. Removing particles improves visibility. Where there is frequent high rainfall, air quality is generally better.

If the rain dissolves gaseous pollutants, such as sulphur dioxide, it can form acid rain resulting in potential damage to materials or vegetation.

Solar radiation

It is important to monitor solar radiation for use in modelling photo-chemical smog events, as the intensity of sunlight has an important influence on the rate of the chemical reactions that produce the smog. The cloudiness of the sky, time of day and geographic location all affect sunlight intensity.

An instrument called a pyranometer measures solar radiation from the output of a type of silicon cell sensor.