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Mountain Rain

April 24, 2007

Pollution from cities could dry out nearby mountains.


How pollution leaves hills high and dry. I’m Bob Hirshon and this is Science Update.

Air pollution from cities can deprive nearby hills and mountains of rainfall. This according to meteorologist Daniel Rosenfeld of Hebrew University in Jerusalem. Looking at fifty years of data from a mountaintop in China, he and his colleagues found that while air pollution has steadily increased, rainfall has decreased.

DANIEL ROSENFELD (Hebrew University, Jerusalem):
Not only that, but when we look into the day to day variability in the amount of rain over the mountain, it is going together with the day to day variability in pollution.

Normally, moist air deflects up a mountainside, then cools and condenses into rain over the mountaintop. But if that moisture condenses on air pollutants, the drops don’t get big enough to fall. Rosenfeld says this effect could dry up alpine watersheds, causing problems for the very cities creating the pollution.

I’m Bob Hirshon, for AAAS, the science society.