19th Conference on Climate Variability and Change


Tropical cyclone strength, related precipitation, and sea surface temperatures ahead of the cyclone tracks

Pavel Ya. Groisman, NOAA/NESDIS/NCDC, Asheville, NC; and R. W. Knight, R. W. Reynolds, T. R. Karl, O. N. Bulygina, and P. Zhai

Interest in possible changes in tropical cyclone (TC) activity and their consequences in the changing climate is mounting. Model simulations using CO2-induced sea surface temperature increases indicate that TC wind speeds and related daily precipitation may increase. Sea surface temperatures (SST) along the southeastern U.S. coast in the hurricane season have increased by ~0.6C during the past century and are correlated with the TC related seasonal rainfall. However, the observed 40% increase in TC related precipitation over the coastal zone of the southeastern United States is not (yet) statistically significant.

Our study quantifies the TC and rainfall relationship, and provides insight into the details of this relationship for several preferred tropical cyclone regions. We investigate changes in the TC-related rainfall distributions (hourly rates and daily totals) as a function of TC strength at landfall and impact of SST ahead of TCs on the TC strength. Our findings are (if past relationships can serve as a faithful predictor of the future) that a warmer climate and (projected with it) SST increases over the tropical North Atlantic and Pacific Oceans will likely be accompanied by more frequent strong landfalling hurricanes over the southeastern U.S. and China coasts. The fraction of strong hurricanes that make landfall on these coasts is positively correlated with daily SSTs in the path of the TCs. There were no landfalling strong hurricanes at, or above Category 3 in the Saffir-Simpson Hurricane Scale (strong to catastrophic hurricanes) when the SST was below 28.3C, which is likely a primary reason of their absence at the Russian Far East coast during the past fifty years.

Stronger TC events are accompanied by higher daily rainfall, which (at least for the United States) will likely be more attributable to prolonged rainfall hours from stronger TC events rather than to changes in mean hourly rainfall rates. Similar assessments for the Russian Far East and China will be presented at the Conference. These conclusions have numerous implications for flooding, soil erosion, and landslide projections associated with TC events in the future ″warm″ climate.

Session 6, Linking weather and climate I
Thursday, 18 January 2007, 8:30 AM-12:00 PM, 214B

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