[GTP] IMAGe GTP Seminar at NCAR--David Schecter

[Silvia Gentile]

Hurricane Formation in Diabatic Ekman Turbulence
David Schecter
NorthWest Research Associates




This study examines the emergence of hurricanes from chaotic swirling 
motions in a 3-layer model of the tropical troposphere that includes 
basic parameterizations of cumulus convection and air-sea interaction. 
The chaotic flow is referred to as Diabatic Ekman Turbulence (DET), in 
order to emphasize that cumulus convection and Ekman pumping are 
critical to its behavior.  The time required for tropical cyclogenesis 
in DET is examined over a broad range of sea-surface temperatures, 
tropical latitudes, and surface exchange coefficients for moist entropy 
and momentum. The mean results show sensible trends, but the specific 
genesis time can vary significantly with subtle details of the initial 
turbulence. Moreover, hurricanes do not always form. In the event that a 
tropical depression develops into a hurricane, the process is highly 
asymmetric. Intensification involves a shear-flow instability, the 
production of mesovortices, and contraction of the basic circulation. 
Despite the complex evolution, the intensification rate is largely 
consistent with the expectations of a quasi-linear stability analysis. 
Properties of mature hurricanes and the nature of their fluctuations are 
briefly addressed in the context of the model.



Monday, February 2, 2009
Foothills Laboratory 2, Room 1001
Lecture 3:30pm