Natural Hazards and Earth System Science www.nat-hazards-earth-syst-sci.net 1561-8633 1684-9981 9 2 2009 10.5194/nhess-9-635-2009 http://www.nat-hazards-earth-syst-sci.net/9/635/2009/ http://www.nat-hazards-earth-syst-sci.net/9/635/2009/nhess-9-635-2009.html http://www.nat-hazards-earth-syst-sci.net/9/635/2009/nhess-9-635-2009.pdf 635 645 2009-04-30 On tropical cyclone frequency and the warm pool area R. E. Benestad rasmus.benestad@met.no Norwegian Meteorological Institute, P.O. Box 43, 0313, Oslo, Norway The proposition that the rate of tropical cyclogenesis increases with the size of the "warm pool" is tested by comparing the seasonal variation of the warm pool area with the seasonality of the number of tropical cyclones. An analysis based on empirical data from the Northern Hemisphere is presented, where the warm pool associated with tropical cyclone activity is defined as the area, A, enclosed by the 26.5°C SST isotherm. Similar analysis was applied to the temperature weighted area AT with similar results. An intriguing non-linear relationship of high statistical significance was found between the temperature weighted area in the North Atlantic and the North-West Pacific on the one hand and the number of cyclones, N, in the same ocean basin on the other, but this pattern was not found over the North Indian Ocean. A simple statistical model was developed, based on the historical relationship between N and A. The simple model was then validated against independent inter-annual variations in the seasonal cyclone counts in the North Atlantic, but the correlation was not statistically significant in the North-West Pacific. No correlation, however, was found between N and A in the North Indian Ocean. A non-linear relationship between the cyclone number and temperature weighted area may in some ocean basins explain both why there has not been any linear trend in the number of cyclones over time as well as the recent upturn in the number of Atlantic hurricanes. The results also suggest that the notion of the number of tropical cyclones being insensitive to the area A is a misconception. Benestad, R. E.: What can present climate models tell us about climate change? Climatic Change, 59, 311–332, 2003. Benestad, R. E., 2006: An explanation for the lack of trend in the hurricane frequency, arXiv: physics/0603195., http://arxiv.org/abs/physics/0603195, March 2006. Bengtsson, L., Hodges, K. I., and Roeckner, E., Storm Tracks and Climate Change, J. Climate, 19, 3518–3542, 2006. Chan, J.: Comments on "Changes in Tropical Cyclone Number, Duration, and Intensity in a Warming Environment", Science, 311, 1713b, \doi10.1126/science.1121522, 2006. Chauvin, F., Royer, J.-F., and Déque, M.: Response of hurricane-type vortices to global warming as simulated by ARPEGE-Climate at high resolution, Clim. Dynam., 27, 377–399, 2006. Chronis, T., Williams, E., Anagnostou, E., and Petersen, W.: African Lightning: Indicator of Tropical Atlantic Cyclone formation, Eos, 88, 397–398, \doi10.1029/2007EO400001, 2007. Chu, J.-H., Sampson, C. R., Levin, A. S., and Fukada, E.: The Joint Typhoon Warning Center tropical cyclone best tracks 1945–2000 report, Joint Typhoon Warning Cent., Pearl Harbor, Hawaii, 2002. Emanuel, K.: Increasing destructiveness of tropical cyclones over the past 30 years, Nature, 436, 686–688, 2005. Gettelman, A., Seidel, D. J., Wheeler, M. C., and Ross, R. J.: Multidecadal trends in tropical convective available potential energy, J. Geophys. Res., 107(D21), 4606, \doi10.1029/2001JD001082, 2002. Goldenberg, S. B., Landsea, C. W., Mestas-Nunez, A. M., and Gray, W. M.: The recent Increase in Atlantic Hurricane Activity: Causes and Implications, Science, 293, 474–479, 2001. Gray, W. M.: A global view of the origin of tropical disturbances and storms, Mon. Weather Rev., 96, 669–700, 1968. Henderson-Sellers, A., Zhang, H., Berz, G., Emanuel, K., Gray, W., Landsea, C., Holland, G., Lighthill, J., Shieh, S.-L., Webster, P., and McGuffie, K.: Tropical Cyclones and Global Climate Change: A Post-IPCC Assessment, B. Am. Meteorol. Soc., 79, 20–38, 1998. Holland, G. J.: The maximum potential intensity of tropical cyclones, J. Atmos. Sci., 54, 2519–2541, 1997. Holland, G. J.: Misuse of Landfall as a Proxy for Atlantic Tropical Cyclone Activity, Eos, 88, 349–356, 2007. Hoyos, C. D., Agudelo, P. A., Webster, P. J., and Curry, J. A.: Deconvolution of the Factors Contributing to the Increase in Global Hurricane Intensity, Science, 312, 94–97, 2006. Jung, T., Gulev, S. K., Rudeva, I., and Soloviov, V.: Sensitivity of extratropical cyclone characteristics to horizontal resolution in the ECMWF model, Research Dept., Technical Memorandum 485, ECMWF, 2006. Klotzbach, P J.: Trends in global tropical cyclone activity over the past twenty years (1986–2005), Geophys. Res. Lett., 33, L10805, \doi10.1029/2006GL025881, 2006. Klotzbach, P. J. and Gray, W. M.: Multidecadal Variability in North Atlantic Tropical Cyclone Activity, J. Climate, 21, 3929–3935, \doi10.1175/2008JCLI2162.1, 2008. Knutson, T. R. and Tuleya, R. E.: Impact of CO2-Induced Warming on Simulated Hurricane Intensity and Precipitation: Sensitivity to the Choice of Climate Model and Convective Parameterization, J. Climate, 17, 3477–3495, 2004. Knutson, T. R. and Tuleya, R. E.: Reply, J. Climate, 18, 5183–5187, 2005. Landsea, C W., Harper, B A., Hoarau, K., and Knaff, J A.: Can we detect trends in extreme tropical cyclones?, Science, 313, 452–454, 2006. Landsea, C. W.: Counting Atlantic Tropical Cyclones Back to 1900, Eos, 88, 197–202, 2007. Lau, K. M., Zhou, Y. P., and Wu, H. T.: Have tropical cyclones been feeding more extreme rainfall?, J. Geophys. Res., 113, D23113, \doi10.1029/2008JD009963, 2008. Lau, W. K. M. and Kim, K.-M.: How Nature Foiled the 2006 Hurricane Forecasts, Eos, 88(9), 105–107, 2007. Mann, M. E., Emanuel, K. A., Holland, G. J., and Webster, P. J.: Atlantic Tropical Cyclones Revisited, Eos, 88(36), 49 pp., 2007. Meehls, G. A., Stocker, T. F., Idlingstein, W. D., Gaye, A. T., Gregory, J. M., Kitoh, A., Knutti, R., Murphy, J. M., Noda, A., Raper, S. C. B., Watterson, I. G., Weaver, A. J., and Zhao, Z.-C.: Climate Change: The Physical Science Basis, United Kingdom and New York, NY, USA, Cambridge University Press, Chap. Global Climate Projections, 2007. Michaels, P. J., Knappenberger, P. C., and Davis, R. E.: Sea-surface temperatures and tropical cyclones in the Atlantic basin, Geophys. Res. Lett., 33, L09708, \doi10.1029/2006GL025757, 2006. Pearce, R.: Comments on "Why must hurricanes have eyes?" – revisited, Weather, 60(11), 329–330, 2005a. Pearce, R.: Why must hurricanes have eyes? Weather, 60(1), 19–24, 2005b. Randall, D. A., Wood, R. A., Bony, S., Colman, R., Fichefet, T., Fyfe, J., Kattsov, V., Pitman, A., Shukla, J., Srinivasan, J., Stouffer, R. J., Sumi, A., and Taylor, K. E.: Climate Change: The Physical Science Basis, Cambridge, UK: Cambridge University Press, Chap. Climate Models and Their Evaluation, 2007. Scharroo, R., Smith, W. H., and Lillibridge, J. L.: Satellite Altimetry and the Intensification of Hurricane Katrina, Eos, 366 pp., 2005. Scharroo, R., Smith, W. H. F., and Lillibridge, J. L.: Reply to Comment on "Satellite Altimetry and the Intensification of Hurricane Katrina", Eos, 87(8), 89 pp., 2006. Smith, R. K.: "Why must hurricanes have eyes?" – revisited, Weather, 60(11), 326–328, 2005. Sun, D., Gautam, R., Cervone, G., Boybeyi, Z., and Kafatos, M.: Comment on "Satellite Altimetry and the Intensification of Hurricane Katrina", Eos, 87(8), 89 pp., 2006. Trenberth, K.: Uncertainty in Hurricanes and Global Warming, Science, 308, 1753–1754, 2005. Trenberth, K. E., Jones, P. D., Ambenje, P., Bojariu, R., Easterling, D., Klein~Tank, A., Parker, D., Rahimzadeh, F., Renwick, J. A., Rusticucci, M., Soden, B., and Zhai, P.: Climate Change: The Physical Science Basis, Cambridge, UK, Cambridge University Press, Chap. Observations: Surface and Atmospheric Climate Change, 2007. Vecchi, G. A., Clement, A., and Soden, B.: Examining the Tropical Pacific's Response to Global Warming, Eos, 89(9), 81 pp., 2008. Vitard, F., Stockdale, T., and Ferranti, L.: Seasonal forecasting of tropical storm frequency, ECMWF Newsletter, 16–22, 2007. Webster, P. J., Holland, G. J., Curry, J. A., and Chang, H.-R.: Changes in Tropical Cyclone Number, Duration, and Intensity in a Warming Environment, Science, 309, 1844–1846, 2005. Wilks, D. S.: Statistical Methods in the Atmospheric Sciences, Orlando, Florida, USA, Academic Press, 1995. Wu, M-.C., Yeung, H., and Chang, W-.L.: Trends in Western North Pacific Tropical Cyclone Intensity, Eos, 87(48), 537 pp., 2006. Yoshimura, J., Masato, S., and Noda, A.: Influence of Greenhouse Warming on Tropical Cyclone Frequency, J. Meteorol. Soc. Jpn., 84(2), 405–428, 2006.