Special Symposium on Aerosol–Cloud–Climate Interactions


Examination of the Arizona precipitation record for evidence of precipitation suppression by air pollution aerosols

Israel L. Jirak, Embry-Riddle Aeronautical University, Prescott, AZ; and A. Keith

Air pollution aerosols generated in industrial and urban areas can serve as abundant, small cloud condensation nuclei, inhibiting the precipitation formation process. This effect has been quantified in previous studies that examined orographic precipitation trends for locations across the western United States and around the world. These studies have found a decrease in the ratio of precipitation for elevated sites relative to upwind, polluted urban sites over the past half century. Meanwhile, similar precipitation trends were not found for more pristine locations, providing evidence of precipitation suppression by air pollution. This study investigates precipitation trends for numerous pairs of polluted and pristine sites across the state of Arizona. The findings of this study support the idea that air pollution aerosols have acted to suppress precipitation downwind of major urban areas in Arizona, especially for wintertime, orographic precipitation. Understanding the extent and magnitude of this effect is important for arid regions like Arizona, where water supply is a significant issue.

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wrf recording  Recorded presentation

Session 5, Aerosol direct and indirect effects
Wednesday, 14 January 2009, 8:30 AM-10:00 AM, Room 131B

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