15.8 Relating Convective Intensity Proxies to Tropical Cyclone Intensity Changes Using 10 Years of TRMM Data

Thursday, 20 August 2009: 9:45 AM
The Canyons (Sheraton Salt Lake City Hotel)
Ellen Ramirez, University of Utah, Salt Lake City, UT; and H. Jiang

While much progress has been made concerning tropical cyclones since the advent of satellite networks, the field continues to struggle with prediction of intensity changes. Tropical cyclone intensity is a complicated function of large environmental and synoptic scale forcing, thermodynamic variables, and dynamical processes. Previous works by the authors and others have established that the convective intensity in the eyewall is related to intensification. It has been suggested recently that strong convection in outer bands are cause for de-intensification (Wang 2009). By definition, the updraft strength is most commonly used to infer convective intensity which unfortunately cannot be measured from orbit. To develop a convective intensity scale for tropical cyclones, other proxies must be established. This study utilizes the 10 years of Tropical Rainfall Measurement Mission (TRMM) Tropical Cyclone Precipitation Feature (TCPF) data to recognize the regions of highest convective intensity and study the relationships between convective intensities in the eyewall and outer rainbands and cyclone intensity change. The convective proxies derived from TRMM that we use for this study are the minimum 85GHz PCT, the minimum 37GHz PCT, the minimum 11 micron brightness temperature, the maximum 20 dbZ echo height, and the lightning count per unit area, etc. The first part of this research established values for the above parameters that correspond to strong convection, with the goal of determining if there is a significant correlation between TCPFs that satisfy this criterion and TCPFs that underwent intensification and rapid intensification. Secondly it was determined if strong convection in outer bands contributes to cyclolysis, presumably by inhibiting the low level moisture flux in the eyewall. The same convective criterion is used in the outer rainband region to infer strong convection, with the goal of determining if convection in this region significantly correlates to storms that underwent de-intensification and rapid de-intensification.
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