The Spatial Pattern of the Sun-Hurricane Connection

We define the spatial response of hurricanes to extremes in the solar cycle. Using an equal-area hexagon tessellation, regional hurricane counts are examined during the period 1851–2010. The response features fewer hurricanes across the Caribbean, Gulf of Mexico, and along the eastern seaboard of the United States when sunspots are numerous. In contrast fewer hurricanes are observed in the central North Atlantic when sunspots are few. The sun-hurricane connection is as important as the El Niño Southern Oscillation in statistically explaining regional hurricane occurrences.  Read more.

How Can Solar Variability Affect Hurricanes?

An inverse relationship between hurricane activity over the Caribbean and the number of sunspots has recently been identified. Here we investigate this relationship using daily observations and find support for the hypothesis that changes in ultraviolet (UV) radiation are the cause. The relationship is statistically significant after accounting for annual variation in ocean heat and the El Nino cycle. A warming response in the upper troposphere to increased solar UV forcing, as measured by the Mg II core-to-wing ratio, decreases the atmosphere's convective available potential energy (CAPE) leading to a weaker cyclone. The response amplitude at a hurricane intensity of 44 m/s is 6.7 m/s +/- 2.56 m/s per 0.01 Mg II units (s.d.), which compares with 4.6 m/s estimated from the heat-engine theory using a temperature trend derived from observations. An increasing response sensitivity with increasing hurricane strength is found in the observations and in an application of the theory. Read more. Citation: 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.

United States and Caribbean tropical cyclone activity related to the solar cycle

The recent increase in the power of Atlantic tropical cyclones is attributable to greater oceanic warmth in part due to anthropogenic increases in radiative forcing from greenhouse gases. However solar activity can influence a hurricane's power as well through changes in upper tropospheric temperature. Here we report on a finding that annual U.S hurricane counts are significantly related to solar activity. The relationship results from relatively more intense tropical cyclones over the Caribbean when sunspot numbers are low. The finding is in accord with the heat-engine theory of hurricanes that predicts a reduction in the maximum potential intensity with a warming in the layer above the hurricane. An active sun warms the lower stratosphere through ozone absorption of additional ultraviolet (UV) radiation. Since the dissipation of the hurricane's energy occurs through ocean mixing and atmospheric transport, tropical cyclones can act to amplify a relatively small change in the sun's output appreciably altering the climate. Results from this study have serious implications for life and property throughout the Caribbean, Mexico, and portions of the United States. The paper is currently under review for publication.