James B. Elsner Department of Geography, Florida State University Climatek, Inc. Acknowledgments: Thomas H. Jagger, Jim Kossin; Funding: NSF, RPI Quantile and Poisson Regression Models in Hurricane Studies 1 January 11, 2009 Phoenix, AZ Trends in lifetime maximum intensity Solar activity and near-coastal hurricane activity

Take-Home Points 3 The strongest tropical cyclones worldwide are getting stronger. The increase in intensity is consistent with Emanuel’s heat- engine theory of tropical cyclone intensity. There is a detectable solar signal in U.S. hurricane activity due to increases in tropical cyclone intensity when the sun is “cooler”. This finding is also in accord with the heat-engine theory. The R program for statistical computing is arguably the best way to analyze and model climate data.

western North Pacificeastern North Pacific North Atlanticsouthern Indian

South Pacificnorthern Indian

Regression of satellite-derived lifetime maximum wind speed onto global SST Regression of best-track lifetime maximum wind speed onto global SST

GFDL Model Data

Together the three covariates explain between 40 and 48% of the variation in tropical cyclone counts depending on start year. But, what is left over?

Percentiles Cyan: 99th Blue: 95th Green: 90th Red: 75th Black: 50th

According to Bister & Emanuel (1998), the potential velocity of a hurricane is proportional to the SST and inversely proportional to the temperature above the hurricane. Thus during a period of inactive sun, the upper atmosphere is cooler increasing the potential hurricane intensity. But this is only over regions of sufficiently warm SST (high oceanic heat content) like the Caribbean and western tropical Atlantic. Over regions of marginal oceanic heat content (eastern tropical Atlantic), SST is the limiting factor for hurricane intensity.

Aug-Oct avg air T vs Aug-Oct SSN count. P is the pressure level with lower values indicating higher elevations. Positive correlation (r) indicates cooler air with fewer SSN.

Summary 32 The strongest tropical cyclones worldwide are getting stronger. The increase in intensity is consistent with Emanuel’s heat-engine theory of tropical cyclone intensity. There is a detectable solar signal in U.S. hurricane activity due to increases in tropical cyclone intensity when the sun is “cooler”. This finding is also in accord with the heat-engine theory. Next: Use R for Climate Research Download and open the tutorial, then get some lunch!tutorial

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