Thursday, May 2, 2013

A possible link between solar activity and tornado activity?

A paper published today in Geophysical Research Letters finds tornado activity in the central US is related to phases of the natural Madden-Julian Oscillation (MJO). Prior research has suggested the Madden-Julian Oscillation is modulated by the 11-year solar cycle. ENSO and the Pacific Decadal Oscillation have also been linked to both tornado activity and solar activity. This begs the question, are changes in solar activity a factor in explaining changes in tornado activity?

Variability of central U.S. April–May tornado day likelihood by phase of the Madden-Julian Oscillation


April–May tornado day likelihood from 1990–2011 was calculated for the central U.S. for phases of the Madden-Julian Oscillation (MJO). An April tornado day was found more likely during MJO phases 6 and 8 and less likely during phases 3, 4, and 7. A May tornado day was found more likely during phases 5 and 8 and less likely in phases 2 and 3. During phases with above-normal tornado day likelihoods, positive anomalies of convective available potential energy, bulk vertical wind shear, and storm-relative helicity were found in the central U.S. Negative anomalies were found during phases with below-normal tornado day likelihoods. Anomalies of such environmental parameters were connected to the MJO via variability in tropospheric circulation. These results provide an important starting point for extended-range prediction of U.S. tornado activity.

1 comment:

  1. Acknowledging the potential unreliability of sunspot number and tornado number by the techniques used to count in the past--The inverse relationship between the number of tornadoes per year versus the number of sunspots (starting when the data for number of tornadoes was first taken) is statistically significant. Though the conservation of angular momentum accounts for a very small change in the Earth's rotation consistent with the sunspot cycle, there may be other residual effects of energy conservation in the Earth/Sun System.