Sensitivity study for the simulation of Tornado/Nor’wester during pre-monsoon season over Bangladesh using high resolution WRF-ARW model

Abstract

Comprehensive sensitivity analyses on physical parameterization schemes of Weather Research and Forecasting (WRF-ARW V3.5.1) Model have been carried out for the simulation of squall/nor'wester on 07 April 2012, 28 April 2012, 27 April 2014 and 15 May 2014 over Bangladesh. Final Reanalysis (FNL) data (l° x l°) from National Centre for Environment Prediction (NCEP), is used as initial and lateral boundary conditions which is updated at six hourly interval i.e. the model is initialized with 0000, 0600, 1200 and 1800 UTC initial fields of corresponding dates. The NCFP FNL data is interpolated to the model horizontal and vertical grids. The model is configured in a single domain, having 3 km horizontal grid spacing with 173x225 grids in the east-west and north-south directions and 15 vertical levels. By using Grads software, the different meteorological parameters, stability indices and energies are obtained, which are related to Nor'wester/squall line. The six different MP schemes used in this research are Kessler, Lin et al., WSM6, Thompson, SBU and WDM6. The meteorological parameters, which have been analyzed, are Wind Speed at 10m Level, Temperature at 2m Level, Sea Level Pressure (SLP), Relative Humidity (RH), Maximum Reflectivity, Latent Heat, MCAPE, MCIN, Total Total Index ('IT), Vertical Total Index (VT). Cross Total Index (CT), K Index (KI), Lifting Condensation Level (LCI.) and Level of Free Convection (LFC) at Dhaka, Chittagong, Sylhet, Khulna and Barisal stations. Significant changes are found by all the MPs coupling with CPs in all the parameters during the time of occurrence of squall/gusty wind. Significant changes are found in all the parameters for all MPs coupling with CPs at Dhaka after 0500 UTC and at Chittagong after 0900 UTC of 7 April 2012, which is delayed almost one and half hours. BMJ has simulated reflectivity at a particular time but KF simulated reflectivity wide range of time over Dhaka and Chittagong on 7 April 2012. Significant changes are found by all the MPs coupling with CPs in all the parameters during the time of occurrence of squall at Barisal and Chittagong on 15 May 2014.