Seeing Pollution from Space

Air pollution is a major issue facing the planet as it is the presence of substances in the atmosphere which are harmful to both living things and the environment. However, satellites can track this pollution from space. To improve air quality, we must first know what contributes to polluting the air. Skies may be hazy from traffic, or industry such as coal burning power plants, or the pollution could be coming from somewhere farther away. Satellite images help identify large areas of pollution caused by fires, dust/sandstorms, volcanic eruptions, large industrial sources, or the transport of man-made pollution from somewhere else. Smaller sources of pollution, such as small industries or local roads won’t be visible in satellite images.

Photos like true colour images a provide a very simple way to see if smoke, dust, or haze is being transported to certain regions. You can access daily true colour images of much of the world from the MODIS Rapid Response System (link to MODIS website: https://modis.gsfc.nasa.gov/). MODIS stands for Moderate Resolution Imaging Spectroradiometer. It is a tool that flies on two NASA satellites and both satellites orbit the Earth from pole to pole. This way MODIS sees the entire Earth everyday and usually provides images within 4/6 hours.

Fires: MODIS records the location of fires on the ground by observing unusual hot spots. They don’t see every single fire but will see large fire that might be contributing to air pollution. In images fires are represented with red dots.

Haze: Haze from cars and power plants are grey-white in true colour images. It is difficult to pinpoint a source, but you can see where the haze is.

Satellites measure the concentration of particles (aerosols) in the atmosphere by observing how much light reaches the surface of the Earth and how much is reflected off the aerosols. The measurement is called aerosol optical depth or aerosol optical thickness.