Sunday, November 11, 2007

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.

1 comment:

Erl said...

I note criticism of your paper on the relation between tropical cyclones and solar activity based on the notion that UV does not heat the upper troposphere. It certainly does. You may be interested to look at my paper at:

It is apparent that temperatures at 200hPa are strongly affected by solar activity. Seasonal variation is about half that in sea surface temperature. Inter-annual variation at 200hPa is about double sea surface temperature. The biggest shift in 200hPa temperature occurred in 1978. Currently 200hPa temperature is plummeting.

Strongest variation in the tropics and near tropics is in September when geomagnetic activity peaks.

There are implications for cirrus density and the occurrence of tropical warming and cooling events that feed into temperatures at high latitudes in winter.