Mechanism of Asymmetric Precipitation by Tropical Cyclone Nada Over the Indian Peninsula

Abstract

The Tropical Rainfall Measuring Mission (TRMM) and ERA5 reanalysis data are used to research the asymmetric precipitation induced by tropical cyclone (TC) Nada, which made landfall on the southeastern coast of the Indian Peninsula on December 2, 2016. The mechanism of asymmetric precipitation is analyzed during the passage of the TC. The results show that the spatial average precipitation rate increased to a maximum of 1.78 mm/hr on the southeastern coast of the Indian Peninsula, where the vorticity of the TC center increased to more than 5 × 10–4 s–1 at 850 hPa at 06:00 UTC on December 1. Near the center of Nada, the troposphere had strong upward convection at a vertical velocity of 0.7 pa/s. The positive (negative) vertical wind shear was located on the left (right) side of the TC path. The maximum value area of wind shear was consistent with the distribution area of extreme precipitation. TC-induced asymmetric rainfall was mainly caused by the superposition of Nada and low-level cold air intrusion, which resulted in unstable atmospheric stratification, uplifting warm and humid air and producing strong convection. This study offers new insights into precipitation induced by the interaction of cold air intrusion and a TC in the northern Indian Ocean.

Keywords

• tropical cyclone
• precipitation
• strong convection
• indian peninsula