11.5
Do auroral atmospheric gravity waves influence mesoscale processes, extratropical and tropical cyclones?
Paul Prikryl, Communications Research Centre Canada, Ottawa, ON, Canada; and D. B. Muldrew and G. J. Sofko
Cases of mesoscale cloud bands in extratropical cyclones are observed a few hours after atmospheric gravity waves (AGWs) are launched from the auroral ionosphere. It is suggested that the solar-wind-generated auroral AGWs seed (trigger a release of) instabilities in the mid-latitude troposphere that initiate convection leading to cloud bands and growth of extratropical cyclones and, if ducted to low latitudes, influence the development of tropical cyclones. The gravity-wave-induced vertical lift may modulate the slantwise convection by releasing the moist symmetric instability in the warm frontal zone of an extratropical cyclone. Latent heat release associated with the mesoscale slantwise convection has been linked to explosive cyclogenesis and severe weather.
The circumstantial evidence of the solar wind influence on extratropical cyclones is supported by a statistical analysis of high-level clouds (<440 mb) extracted from the International Satellite Cloud Climatology Project (ISCCP) D1 dataset. A statistically significant response of a high-level cloud area index (HCAI) to fast solar wind from coronal holes is found in extratropical and tropical latitudes during autumn-winter and spring-summer, respectively. In the extratropics, this response of the HCAI to solar wind forcing is consistent with the effect on tropospheric vorticity found by Wilcox et al. (1974).
Wilcox et al., 1974: Influence of solar magnetic sector structure on terrestrial atmospheric vorticity. J. Atmos. Sci., 31, 581–588.
Recorded presentationSession 11, Mulitscale processes, atmospheric waves
Wednesday, 8 August 2007, 3:15 PM-4:30 PM, Waterville Room
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