Simulation of track and intensity of TCs over Bay of Bengal: Sensitivity to micro physics and Cu parameterization schemes

Abstract

Under the influence of climate change the frequency and severity of Tropical Cyclones is increasing alarmingly. It has become very important to define appropriate models that produce the best estimates of incoming cyclone parameters ([5], [6]). With this objective in mind, the impact of cloud microphysics and cumulus parameterization schemes is evaluated for the simulation of Track and Intensity of Very Severe Cyclonic Storm (VSCS) ‘VARDAH’ formed in 6th –13th December 2016 and Severe Cyclonic Storm (SCS) ‘MORA’ formed in 28th – 31st May 2017 over south Andaman Sea and adjoining southeast Bay of Bengal (BoB). The cloud microphysics provides estimation of atmospheric heat and moisture tendencies, formation of cloud droplets, accounts for the vertical flux of precipitation and sedimentation process. The cumulus parameterization vertically redistributes heat and moisture independent of latent heating due to precipitation ([3], [4]). The Advance Research WRF mesoscale model is configured with single domain of 9 km resolution for the region covering the BoB ([7]). Simulations are performed with NCEP GFS 0.5⁰ analysis and forecasts for initial/boundary conditions. Track location, wind and MSLP associated with Vardah and Mora are simulated for five different schemes (Table 1) that are combinations of Cloud Microphysics and Cumulus parameterization schemes and validated with IMD observations ([8], [9]).The simulated maximum sustained winds and central pressure calculated using five different combination of Cloud Microphysics and Cumulus parameterization schemes has been analysed in order to observe the impact of the combination of scheme on the simulation of cyclone. It was observed that a combination of Betts-Miller-Janjic and WSM 6-class Schemes (5th Scheme combination) seems to give the best results. The central pressure follows a similar trend with all schemes, however 3rd and 5th scheme combinations perform better when it comes to wind speeds, 1st, 2nd and 4th schemes seem to overestimate the winds at and post landfall.