Contributions of Various Temporal Components of Large-Scale Parameters in Tropical Cyclone Genesis over the North Indian Ocean

Abstract

This work compares the contributions of synoptic, intraseasonal, and interannual components of large-scale parameters to tropical cyclone (TC) genesis over the North Indian Ocean (NIO) from April to December from 1979 to 2020. A composite analysis is employed with respect to TC genesis time and location. It is shown that most TCs occur when the total sea surface temperature (SST) is between 28 and 30 °C and SST anomalies in three time ranges are small (with the magnitude less than 0.2 °C). The TCs form mostly when the anomalies of vertical zonal wind shear are between −6 and 6 m s−1 and total vertical zonal wind shear falls within −12 and −3 m s−1, with the synoptic component being a positive contributor. The intraseasonal component of vorticity and convergence in the low level, vertical motion and specific humidity in the middle level, and convection contributes dominantly to the TC genesis. Synoptic-scale tropical disturbances obtain barotropic kinetic energy from the climatological mean and intraseasonal flows, with the former dominant in the southeastern sector, and the latter dominant in the northwestern sector. The contributions of the three temporal components of environmental factors are compared for TC genesis between the Arabian Sea (AS) and Bay of Bengal (BOB) and between the early season (April through June) and late season (September through December). The relative contributions of the three temporal components of factors are also compared for the TC formation among the NIO, northern tropical Atlantic Ocean (NTA), Northwestern Pacific (WNP), and Northeastern Pacific (ENP).

Interdecadal variability of the pre-monsoon cyclone characteristics over the Bay of Bengal

“…Therefore, it is quite difficult to determine intensity accurately. Dai et al (2023) reported that the synoptic component plays a beneficial role in the formation of TCs over NIO when vertical zonal wind shear anomalies fall between −6 and 6 m s −1 and total vertical zonal wind shear falls between −12 and −3 m s −1 . Geetha and Balachandran (2014) have investigated the decadal changes of the cyclonic disturbances over the NIO basin for the past five decades , which comprise depressions and all TC classifications.…”

A Zonal See‐Saw Variation of Tropical Cyclogenesis Over the Arabian Sea and Bay of Bengal‐South China Sea

“…One of the essential requirements for the TCs that are generated over the NIO and SCS is the favorable atmosphere circulations, which are modulated locally and remotely by the sea surface temperature (SST) deviations in the tropics of the Indian and Pacific Oceans (Camargo et al., 2009; Cao et al., 2018; Chan, 2008; Chen, 2011; Dai et al., 2023; Girishkumar & Ravichandran, 2012; Gray, 1968; Singh & Roxy, 2022; Wang & Chan, 2002) and heating effect over the Tibetan Plateau (Duan et al., 2012; Wu et al., 2012). The El Niño‐Southern Oscillation (ENSO) makes a substantial influence on environmental conditions over the NIO (Balaguru et al., 2016; Fan et al., 2019).…”

“…The AS and BOB experience a bimodal distribution of TCs on a seasonal time scale, which is attributed to adverse large-scale environment prevalent during the monsoonal period (Li et al, 2013;Priya et al, 2022). The highest occurrence of TCs over the AS and BOB is observed in the period of September-December, along with a subordinate peak in the period of April-June (Dai et al, 2023;Li et al, 2013). The SCS TC formation reaches maximum in September, while the TCs forming over the western North Pacific peaks in August (Cao et al, 2018;Li, 2012).…”