Recorded presentationJ3.2
Changes in number and intensity of tropical cyclones
William M. Briggs, Weill Cornell Medical School, New York, NY
Bayesian statistical models were developed for the number of tropical cyclones and the rate at which these cyclones became hurricanes and category 4+ hurricanes in the North Atlantic, North and South Indian, and East and West Pacific Oceans. We find that there is small probability that the number of cyclones worldwide has increased since 1975. The North Atlantic has seen an increase, but the North Indian and West Pacific (since 1990) have seen decreases. The rate at which these storms become hurricanes appears to be constant since 1975. The rate at which hurricanes evolve into category 4+ storms does appear to have increased and this is due to the increasing variability in individual storm intensity. We investigates storm intensity by measuring the distribution of individual storm lifetime in days, storm track length, and Emanuel's power dissipation index. We find little evidence that, overall, the mean of the distribution of individual storm intensity has changed since 1975, but the variability of the distribution has certainly increased. Intensity has actually decreased (in days and track length) since 1990: the power dissipation has likely increased in the North Indian and decreased in the East Pacific. The cold tongue index and the North Atlantic oscillation index were found to be strongly associated with storm quality in the Western, and to a smaller extent, the Eastern Pacific oceans. The North Atlantic oscillation index was strongly associated with the increase in the rate of strong storms evolving. Recorded presentation
Joint Session 3, Tropical Cyclones and Probability/Statistics 1
Tuesday, 22 January 2008, 8:30 AM-9:45 AM, R02-R03
Previous paper Next paper