Professor Da-Lin Zhang

(Department of Atmospheric and Oceanic Science, University of Maryland)

On the Rapid Intensification of Tropical Cyclones

What UG Homepage GR Tarbell Lecture in Meteorology
When Sep 23, 2015
from 03:30 pm to 04:30 pm
Where 112 Walker Building
Contact Name Dave Stensrud
Contact email
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Da-Lin Zhang UMD

The subject of rapid intensification (RI) of tropical cyclones (TCs) has mostly been discussed from environmental factors owing to the lack of high-resolution data in inner-core regions. Our recent studies show that rapid intensifying TCs often exhibit an upper-level warm core or double warm cores having one in the midtroposphere and the other in the lower stratosphere. The upper-level warm core is generated by the subsidence of stratospheric air associated with the detrainments of convective bursts (CBs). It is found that the development of CBs precedes RI, but most subsidence warming radiates away by gravity waves and storm-relative flows. The upper-level warm core forms only after the upper-level inertial stability increases and static stability decreases both sharply 2-3 h prior to RI. In contrast, many fewer CBs occur during RI, but more subsidence warming contributes to a balanced upper-level cyclonic circulation in the warm core (as intense as 20°C) region. Thus, sign ificant C B activity in the inner-core regions is an important ingredient in generating the upper-level warm core that is hydrostatically more efficient to the RI of TCs, given all the other favorable environmental conditions. Our work also shows that rapidly intensifying TCs may occur without an eyewall contraction. The associated dynamical and thermodynamical processes will be discussed during my presentation.