Weather--How Does It Fit into the Air Quality Puzzle?

Predicting how air pollution levels will change over time can be a complicated process.

How far will the pollution spread?

Will it get worse?

What health precautions should be taken?

How long will it last?

To piece the answers together these factors should be considered: emissions, solar radiation, topography, and weather.

Emissions

The characteristics of polluted air depend on the type, size, and number of emitting sources.

Solar Radiation

Solar radiation causes emissions to react chemically which produces more air pollution. Nitrogen oxides (NOx) + volatile organic compounds (VOCs) = ozone.

Topography

Air pollutants can get trapped in valleys when upward air motion is inhibited by inversions.

Weather

Wind

Wind can disperse air pollutants (reduce concentrations) and/or transport pollutants far from their sources. High winds can cause fugitive dust if conditions are dry.

Pressure

Low pressure is often associated with winds, clouds, and precipitation which means there are typically less pollutants. *Exception: high winds that cause fugitive dust when conditions are dry.

High pressure is often associated with calm winds and clear skies. Stagnant air = more pollutants.

Precipitation

Precipitation tends to wash pollutants out of the air.

Clouds

Clouds scatter, reflect, or absorb sunlight which affects the amount that reaches the ground. Emissions + sunlight = ozone (air pollutant).

Temperature

High temperatures speed up the chemical reactions of air pollutants.

Increasing temperature with height characterizes an inversion (pollutants get trapped under the inversion near the ground).

Conclusion

Weather can significantly influence air quality conditions. Understanding this influence is essential to protecting our health when pollution levels are high.