Vertical structure of North Indian Ocean tropical cyclones: A composite analysis using TRMM and GPM

Abstract

The present study deals with the vertical structure of Tropical Cyclones (TC) from 2010 to 2020 over the North Indian Ocean (NIO) using the Tropical Rainfall Measuring Mission (TRMM) and Global Precipitation Measurement Mission (GPM). We analyzed 31 TC which were characterized as severe cyclonic storms, very severe cyclonic storms, and super cyclones out of which 18 occurred over the Bay of Bengal and 13 over the Arabian Sea. The normalized intensity difference method of brightness temperature is used to distinguish the regions of the TC into eyewall, inner rainband, outer rainband, and outer region after identifying the eye. The eye radius (R_e) of the cyclone is used to define the annular regions. The vertical structure is explored using the reflectivity in each region of the cyclone and also with respect to convective precipitation, stratiform precipitation, and sea surface temperature. The intensity of the convection in the eyewall and the rainbands is strong and reaches up to an altitude of 14 km. The outer rainbands were more of stratiform nature and a distinct bimodal distribution is observed with a peak below and above the bright band. The outermost region exhibited the characteristics of both the convective and stratiform, however, the intensity is observed to be less. The convection is observed to be strong in the eyewall for high SST compared to the marginal, however, the vertical extent is large in the marginal SST. The vertical structure of the TC over the NIO contained a wider distribution of reflectivity and vertically extended compared to that of the cyclones in the other oceanic basins.