+ Visit NASA.gov + Advanced Search   + About the Server   + Animation List   + How to Use the Server Previous Animation Next Animation Pollution Reduces Winter Precipitation In winter, moist air flows off the ocean and rises over the hills downwind of a coastal city, dropping its rain and snow mainly as it ascends the hills. As pollution from the city is pushed into the clouds by the hills downwind of the city, it interferes with droplet formation in the clouds as observed by NASA's satellites. The smaller cloud droplets convert more slowly into precipitation. Instead of precipitating, much of the water in the clouds evaporates, reducing the net rainfall downwind of the urban area by up to 15% to 25% on a seasonal basis. First is the unpolluted case.    This animation shows what winter precipitation is like when pollution is not involved. Duration: 19.0 seconds Available formats:   320x240 (30 fps) MPEG-1   2 MB   720 x 486     Frames   320 x 240     PNG           113 KB   160 x 80       PNG           24 KB   80 x 40         PNG           6 KB How to play our movies    This animation shows what winter precipitation is like when pollution is involved. Duration: 19.0 seconds Available formats:   720 x 486     Frames   320x240 (30 fps) MPEG-1   2 MB   320 x 240     PNG           112 KB   720x480 (29.97 fps) MPEG-2   14 MB   640x480 (29.97 fps) MPEG-4   6 MB   160 x 80       PNG           24 KB How to play our movies Animation Number: 10011 Animator: Susan Twardy (Lead) Studio: CI Lab Completed: 2003-12-03 Scientist: Daniel Rosenfeld (Hebrew University) Writer: Kathryn A. Stofer Goddard TV Tape: G2003-067 Keywords: SVS >> Byrne SVS >> Coastal City SVS >> Earth Science SVS >> Gonnelli SVS >> Pollution SVS >> Precipitation SVS >> Rainfall SVS >> Urban SVS >> Winter     Please give credit for this visualization to NASA/Goddard Space Flight Center Conceptual Image Lab Back to Top + Privacy Policy and Important Notices + Reproduction Guidelines NASA Official: Content Contact: Curator: