Saturday, March 22, 2008

Topography and Rainfall Bands

This week, I took a bit of time each day to clean up my desk at work. The stack of unread issues of Eos, Physics Today and BAMS (Bulletin of the American Meteorological Society) was about to topple over.

BAMS wrote a short piece about Corene Matya's research, combining meteorology and geography. Science Daily has a good synopsis here. She showed that the most intense rain bands (aka rain shields) of hurricanes after landfall coincided with the underlying topography. She combined GIS information about terrain elevation with radar measurements of rain shields and discriminant analysis methodology.
With hurricanes crossing Texas hill country, the rain shields tend to line up parallel to the main axis of the hills, running west to east. Storms near the Appalachians also line up parallel to the mountains, whose axis runs southwest to northeast, with the heaviest rain consistently occurring to the west of the track.
West of the Appalachians is the leeward side. This agrees with Rob's simulations and my rain gauge observations in February 2008 Rainfall II. Although we aren't talking about hurricanes here in LA, we do have a similar situation when the Pacific storms' airmasses encounter colder and dryer continental air as they cross the coastal hills and mountains.

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