On the relationship between intensity changes and rainfall distribution in tropical cyclones over the North Indian Ocean

Abstract

AbstractUsing Tropical Rainfall Measuring Mission rain estimates the relationship between rainfall and intensity changes in tropical cyclones (TCs) over the North Indian Ocean (NIO) based on 71 TCs during 1997–2017 is investigated. The axisymmetric analyses revealed that climatologically the Bay of Bengal (BoB) TCs produce extremely heavy rainfall (~9–10 mm⋅hr−1) and Arabian Sea TCs produce very heavy rainfall (~7–8 mm⋅hr−1) in the storm inner core region (0–100 km). The inner‐core region receives three times higher rainfall than the outer region (100–300 km). The left‐forward sector experiences the maximum rainfall for any TC intensity over the NIO basin. A significant increase (decrease) in the rain rate is seen during normal to rapid intensification (weakening) phase. A notable decrease in rainfall of ~4.3 mm⋅hr−1 is observed for the rapidly weakening TCs. Slow‐moving TCs are generally stronger and produce heavy rainfall (2–4 mm⋅hr−1) up to ~300 km storm radius. As the translation speed increases, rainfall gradually shifts from rear to the forward sector of the TC. The asymmetry (wavenumber‐1) in TC rainfall structures revealed that rainfall maximum is located in the left‐forward sector for almost all intensity stages. The amplitude of wave number‐1 asymmetry in TC rainfall shows cyclonic shift as the TC intensity increases and is particularly prevalent in the BoB region. These analyses would be helpful as a baseline for evaluating the performance of numerical models and to identify the vulnerable areas for TC heavy rainfall.