Aerosols and Weather

Key Investigator: Douglas L. Westphal

In nature, aerosols (dust and smoke) and weather interact in an intricate fashion. A long, dry weather pattern, or drought, can lead to forest fires and dust storms. While in the atmosphere, the smoke and dust disturb incoming sunlight and may cause a cooling of the earth's surface. Conversely, the aerosols may trap longwave energy and cause surface warming and a continuation of drought. Thus, our long-term weather (or climate) could change if large quantities of aerosols remained in our atmosphere for extended periods of time.

A computer model has been developed to help quantify these complex interactions. Computer models are less expensive than making measurements from aircraft. Also, the net effect (cooling or warming) of the aerosols cannot be measured easily. This model is analogous to the one used by the National Weather Service for day-to-day weather forecasts. It incorporates information about winds, temperatures, and rainfall. Further, it includes aerosol and radiation information to study the long-range transport and removal of atmospheric aerosols and the effects of surface cooling and warming.

In 1982, a single forest fire in British Columbia, Canada, emitted nearly one billion pounds of smoke which, in just a few days, was transported by the wind across North America to the Atlantic Ocean. Figure 1 is a satellite image of the smoke's location. We used our models to show that the smoke plume was sufficiently dense to reduce the surface temperatures by as much as 8 degrees Fahrenheit, as seen in Figure 2 . The models also showed that the effect was short-lived because one-half of the original smoke mass was removed from the atmosphere by rainfall after only two days.

RESEARCH SITES: Canada, North America

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