Investigation of the microphysical processes during the rapid intensity changes of tropical cyclones over the Bay of Bengal: A modelling approach

Abstract

Tropical cyclones (TCs) are one of the natural destructive weather phenomena. The accurate prediction of TC intensity is dependent on the understanding of the physical processes behind that. This study exposes the importance of microphysical (MP) processes in the rapid intensity changes of cyclones. For this, tropical cyclone simulations were made from the WRF model with a double nested (9 km-Static and 3 km-moving nests) configuration. This study shows that the heating generated by the MP processes in the TC’s inner-core region is highly (moderately) correlated with precipitated (non-precipitated) hydrometeors. During the rapid intensification (RI) period, heat-released microphysical processes such as condensation, freezing due to the accretion of liquid hydrometeors with ice particles, and deposition, etc., are dominant as compared to cooling-induced processes. In addition, the saturated envelope in the TC Phailin (2013) is responsible for more convection, heating, and hence consecutive RI episodes. While dry air intrusion hampers the prolonged RI episodes in TC Fani (2019). However, rapid weakening (RW) in TC Lehar (2013) is promoted by asymmetric, limited convection, and hence, lesser heating. During this RW period, the warm rain (ice) microphysical processes mainly produce heating (cooling).