Understanding North Indian Ocean Tropical Cyclones Through Numerical Modeling: A Comprehensive Investigation of Dynamic and Thermodynamic Properties

Abstract

The constraints posed by the availability of relevant observations and resolution of analysis data sets over the North Indian Ocean (NIO) elucidate the compulsions of numerical modelling studies for understanding the intricate mechanisms governing extreme weather events such as tropical cyclones (or TCs). This study comprehensively investigates Bay of Bengal (BOB) TCs, emphasizing dynamic, thermodynamic, and microphysical/macro-physical characteristics. Employing Weather Research and Forecasting (WRF) modelling with three-dimensional variational data assimilation (3DVAR), the study highlights the dynamic and thermodynamic characteristics associated with BOB TCs during the 2001-2020 pre-monsoon and post-monsoon seasons. Two sets of numerical simulations are conducted: the CTRL experiment without data assimilation and the WRFDA experiment, with data assimilation. The CTRL simulations are initialized with NCEP-FNL and NOAA Sea surface temperature (SST) datasets, and DA simulations consider modified initial conditions generated employing the data assimilation technique using scatterometer wind datasets. Results demonstrate that DA simulations consistently yield comparable predictions for CS and SCS type of TCs in pre-monsoon conditions while underestimating temperature and potential temperature anomalies for HICS type of TCs. CTRL simulations predominantly overestimate dynamic parameters for all categories, whereas it underestimates thermodynamic parameters. The study also provides insights into the TC vertical structure through a composite analysis by highlighting the performance of both simulations to capture dynamic and thermodynamic features, closely aligned with IMDAA data