21st Conference on Climate Variability and Change


The impact of tropical cyclone size on North Atlantic ACE and PDI

Angela M. Fritz, Georgia Institute of Technology, Atlanta, GA; and J. I. Belanger and J. A. Curry

Climatologies of hurricane activity such as Accumulated Cyclone Energy (ACE) and Power Dissipation Index (PDI) are produced by integrating over the life cycle of the storm using maximum surface wind speeds. However, these calculations ignore the size of the tropical cyclone, which varies substantially and is independent of maximum intensity. Integrating over the size of the tropical cyclone could provide a better estimate of potential damage from a TC and can also provide a more accurate index of how tropical cyclones are responding to changes in global climate. We use two data sets of tropical cyclone size: the Extended Best Track (1988-2007) and U.S. landfall size (1920-2007). The radius of outer closed isobar is used to determine TC size in both data sets. The pressure-wind relationship model of Holland (1980) is used to provide 2-dimensional winds for each tropical cyclone. Analysis is done to compare the traditional ACE and PDI estimates (using only the maximum surface wind) with the new estimates that are integrated over the size of the tropical cyclone. Incorporation of size into the indices produces a more accurate assessment of the strength of a tropical cyclone in terms of kinetic energy and landfall impact, and is more suited for use in climate trend studies.

Poster Session 4, Tropical cyclones and monsoons - posters
Tuesday, 13 January 2009, 9:45 AM-11:00 AM, Hall 5

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