Regional variability of precipitation characteristics in Tropical Cyclones over the North Indian Ocean from GPM-DPR measurements

Abstract

Global Precipitation Measurement mission (GPM) satellite carries a dual-frequency precipitation radar (DPR) which provides the three-dimensional structure of precipitating systems with a coarser spatial resolution of 5 km. GPM measurements provide a unique opportunity to examine the microphysical properties of precipitating systems over the ocean, where direct precipitation measurements are extremely rare. The present study uses GPM-DPR products such as surface rainfall rate, radar reflectivity factor, storm top height, mass-weighted mean diameter (Dm), and normalized intercept parameter (Nw) to examine the regional variability of precipitation characteristics in Tropical Cyclones (TCs). The precipitation characteristics are investigated in the Eye Wall (EW), Inner Rain band (IR), and Outer Rain band (OR) regions of TCs over the North Indian Ocean using 8 years of GPM-DPR data (2014–2021). The variation in precipitation characteristics is quantified in the light of predominant precipitation regimes and microphysical processes in different regions of TCs over two oceanic basins Arabian Sea (AS) and the Bay of Bengal (BOB). Our results suggested that the storms are more intense (higher reflectivity), taller and characterized by higher surface rain intensity with bigger Dm and higher Nw in the EW region as compared to the IR and OR regions. The stratiform rain fraction dominates over convective rain fraction in IR and OR regions of TCs. However, stratiform rain fraction is comparable to convective rain fraction in EW region of TCs over BOB. The two dimensional frequency distribution (CFAD) exhibits highly concentrated (broadly distributed) reflectivity values in EW (OR), whereas IR region depicts intermediate characteristics of EW/OR regions. Raindrops encounter significant amount of growth in convective rainfall than stratiform in EW region. The coalescence/break up process is relatively more apparent in EW region of TCs over BOB. Though the bulk of precipitation features are commonly observed over AS and BOB, EW regions of TCs show distinct features over AS and BOB. The observed variations in the precipitation and DSD characteristics have implications for cloud modeling parameterization schemes over the NIO.