2011-02-18: Satellite measurements provide information on the chemical composition of aerosols

A KNMI study uses satellite data from the Dutch Finnish OMI and the U.S. MODIS instruments to provide global information on the composition of anthropogenic (“man-made”) aerosols. Aerosols are important for climate forcing, but the magnitude of these effects is poorly quantified.
Aerosols are particles suspended in air. Aerosols can be made of for example soot, sea salt, desert dust, and also condensed gases. An important part of the aerosols are formed from human activities, for example emissions of traffic and industry. Aerosols are important for climate because they scatter and absorb sunlight and can change the properties of clouds. Because aerosols can be composed of many different substances and their size can strongly vary, the knowledge of their climate effects is still limited.

Most of the anthropogenic aerosol particles are formed in the air from gases like nitrogen dioxide, sulfur dioxide and organics. This study investigates the relation between the concentrations of these gases and the concentrations of the aerosols. Therefore, observations of the Dutch-Finnish OMI instrument and the U.S. MODIS instrument have been used. By using global satellite data, different regions on Earth can be compared directly.
Satellites provide information on pollution controls. Low values (blue): effective pollution control; high values (red): no or little pollution control.
The results of the study show clear relations between the emission of the gases and the aerosols which are formed from them. For example, in Europe we find a difference between west and east Europe for the period 2005-2007. We can explain this difference by a larger emission of the gas sulfur dioxide in east Europe.
The aerosol and nitrogen dioxide satellite observations are used to derive an index that indicates the amount of pollution control (e.g. stack emission controls). The concentration of nitrogen dioxide is used as a measure of the total amount of burning processes. When the aerosol concentrations from burning processes are relatively high, then the index gives a high value. When pollution controls are effective, the aerosol concentrations are relatively low and the index gives lower values. The lowest values for the index are found over the industrial regions in Europe and the U.S., were many pollution control measures are in place. In industrial regions in Asia higher values are found. The highest values are found in regions in South America and Africa, caused by biomass burning to clear land for agriculture.

This study shows that satellite data provides unique global information on aerosols and their relation with the gases from which they are formed. This information can be used to predict reductions of the aerosol concentrations due to pollution control measures and the resulting climate effects.

Link to the article.