Reply to Comment on ``Downward trends in the frequency of intense Atlantic hurricane during the past five decades"

Reply to Comment on
``Downward trends in the frequency of intense Atlantic hurricane during the past five decades"

(Geophysical Research Letters, 24, 2205,1997)

Christopher W. Landsea
NOAA/AOML/Hurricane Research Division , Miami , Florida, USA

Neville Nicholls
Bureau of Meteorology Research Centre, Melbourne, Victoria Australia

William M. Gray
Department of Atmospheric Science, Colorado State University, Fort Collins, Colorado, USA

Lixion A. Avila
National Hurricane Center, Miami, Florida, USA


We thank Dr. Wilson for pointing out that the intense hurricane downward trend is better described as an active followed by a quiescent regime. The apparent sudden drop in hurricane frequency around the late 1960s also has been noted in Gray (1990) and Landsea (1993). Landsea et al. (1996) fitted a linear trend to the hurricane numbers to emphasize the overall long-term change that has taken place. In particular, we wished to emphasize that there has not been an upward trend in hurricane numbers, despite suggestions that such a trend might result from an enhanced greenhouse effect. We did not mean to imply that the decline in the numbers of hurricanes simply reflected a linear trend. We agree with Dr. Wilson, and with the analyses in Gray (1990) and Landsea (1993), that a more accurate description is that of an active regime during the 1940s through the 1960s, followed by a quiet period during the 1970s through the early 1990s, rather than a simple, linear downward trend in numbers.


References

Gray, W. M., Strong association between West African rainfall and US landfall of intense hurricanes. Science, 249, 1251-1256, 1990.

Landsea, C. W., A climatology of intense (or major) Atlantic hurricanes. Mon. Weath. Rev., 121, 1703-1713, 1993.

Landsea, C. W., N. Nicholls, W. M. Gray, and L. A. Avila, Downward trends in the frequency of intense Atlantic hurricanes during the past five decades. Geophys. Res. Lett., 23, 1697-1700, 1996.