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NASA Confirms Rainy Cities
Devil's BSD writes: "It's true, urban areas are rainier than rural areas. Using the Tropical Rainfall Measuring Mission satelite to measure rainfall around cities, NASA found that areas downwind from cities had up to 116% more precipitation than those upwind from it. The cause? The major heat difference, up to about 10 degrees Fahrenheit (5.6 Celsius degrees), caused by the asphalt and concrete in cities. This story is posted on the Goddard Space Flight Center page."
I'm no meteorologist, but it seems to me that there's a world of difference between conditions that produce clouds and conditions that cause clouds to precipitate out. Rising warm air may build a cloud, but without a coincident drop in temperature or air pressure, I don't see how that could translate to more rain in the cities. In fact, I'd suspect the heat island would reduce rain in the cities and increase rain outside of the cities.
Their model seems primarily to be: we noticed that this condition exists and this other condition exists too; perhaps through some mysterious not-precisely-known interaction of the one is causing the other.
The fact that rainfall is presumably (I'm not sure the observation is meaningful without comparative historical data) greater in the cities as well as downwind from the cities suggests another causative factor to me. The already posited airborn particulate output of cities seems to be a much stronger explanation in my opinion.