Examining the Evolution of Precipitation and Convective Features in Rapidly Intensifying and Slowly Intensifying Tropical Cyclones Using 16 Years of TRMM Data

The prediction of tropical cyclone (TC) intensity change, especially the rapid intensification (RI) is one of the greatest challenges to forecasters. Previous studies have shown that precipitation and convective properties are associated with RI. Particularly, the contributions of different precipitation types show differently to the symmetry pattern that leads to RI using the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) dataset (Tao et al. 2017). Tao et al. (2017) examined the evolution of different precipitation and convective parameters in RI events, but did not investigate that for slow intensification (SI) events. They did not quantify the degree of symmetry of these parameters either. The differences and similarities of precipitation and convection features between RI and SI events are important to improve RI forecasting. Therefore, this study aims at comparing the evolution of precipitation and convective features during RI versus SI events, in order to differentiate RI from SI using precipitation and convective properties, including their degree of symmetry.

Using a 16-yr (1998-2013) Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) observations for global TCs, this study examined the evolution of precipitation and convective properties during RI and SI events by classifying overpasses into three categories including “before RI/SI”, “during RI/SI”, and “RI/SI ending” for each RI or SI event. Stratiform precipitation, deep convection, and shallow convection in TCs will be separated using the precipitation/convection classification method developed by Jiang et al. (2018) based on the combined TMI 37 GHz and TRMM PR observations. Properties to be examined include rainfall derived from TMI, 37 and 85 GHz Polarization Corrected Brightness Temperatures (PCTs), and occurrences of stratiform precipitation, deep convection, and shallow convection. Both the composite mean values and the axisymmetric indices (as defined by Shimada et al. 2018) of these parameters will be examined. The 2-D shear-relative composites and Hovmöller diagrams of evolutions of these rainfall and convective properties in RI and SI events will be compared.