Impact of Environmental Moisture on the Intensification of Tropical Cyclone in the Bay of Bengal using WRF-ARW Model

Abstract

Comprehensive sensitivity analysis on physical parameterization schemes of Advanced Weather Research and Forecasting model (ARW-WRF v3.8.1) has been carried out for the impact of environmental moisture on the intensification of TC Hudhud and TC Mora, which formed in the Bay of Bengal and crossed the eastern coast of India on 12 October 2014 and Bangladesh on 30 May 2017 respectively. The initial and boundary conditions of tropical cyclone (TC) are drawn from the global operational analysis and forecast products of National Center for Environmental Prediction (NCEP-GFS) available for the public at 1°×1o resolution. The model was run by using WSM6-class graupel, Thomson graupel, WDM6-class graupel and NSSL momentum-1 microphysics (MP) schemes coupling with Kain-Fritsch (KF) cumulus parameterization (CP) scheme and four different initial conditions of each cyclone. The model domain consists of 8-24oN and 77-96oE and has 9km horizontal resolution with 19 vertical sigma levels. The model was run for 168, 144, 120 and 96-h using the initial conditions at 0000 UTC of 6, 7, 8 and 9 October 2014 for TC Hudhud and 0000 UTC of 25, 26, 27 and 28May 2017 for TC Mora. We have considered (17-20oN & 85-88oE) and (7-10oN & 92-95oE) positions of TC Hudhud and (20-22oN & 88-92oE) and (8-10oN & 86-90oE) positions of TC Mora as the front and rear positions of TCs respectively to analyze the impact of environmental moisture on the intensification of TC. Track of TCs, Maximum wind speed at 10m level, Minimum Sea level pressure (SLP), Convective available potential energy (CAPE), Convective inhibition (CIN), Relative Humidity (RH), Specific Humidity (SH), Water vapor mixing ratio (WVMR) at 2 meter level, Temperature anomaly, Wind speed (WS) and Wind direction (WD) at different levels have been simulated and analyzed in rear and front positions. The area average CIN, WVMR, RH, WS, SH, and temperature are found to increase in front and rear position continuously for all MPs before the landfall for all initial conditions. CAPE is found to increase at front position and decrease at rear position with respect to time for all initial conditions. Due to the northeasterly to easterly wind from surface to 200 hPa level during 8-10 October 2014 and southeasterly wind on 11 October at front position the TC Hudhud moved towards eastern coast of India and for southwesterly wind in the upper troposphere during 27-29 May 2017 and westerly wind at all levels on 30 May the TC Mora moved towards Bangladesh coast.