Daily Tropical Cyclone Intensity Response to Solar Ultraviolet Radiation

In accord with the heat]engine theory of tropical cyclone intensity [Emanuel, 1991; Holland, 1997], the strongest tropical cyclones are getting stronger worldwide with the trend related to increases in oceanic heat content [Trenberth, 2005; Emanuel, 2005; Webster et al., 2005; Elsner et al., 2008]. Yet according to the theory, tropical cyclone wind speeds are inversely related to the temperature of the air near the top of the cyclone so warming at these upper levels should decrease cyclone intensity. Indeed, a recent study shows fewer strong tropical cyclones over the Gulf of Mexico and the Caribbean Sea when sunspot numbers are high [Elsner and Jagger, 2008]. Here we provide new insight into this intriguing relationship by showing the response amplitude of the intensity change is quantitatively consistent with the heat]engine theory, and demonstrating that the relationship is likely the result of changes in UV radiation rather than the result of changes in other physically related variables including total solar irradiance, radio flux, and galactic cosmic rays.

Elsner, J. B., T. H. Jagger, and R. E. Hodges (2010), Daily tropical cyclone intensity response to solar ultraviolet radiation, Geophys. Res. Lett., 37, L09701, doi:10.1029/2010GL043091.