Impact of microphysics parameterizations and horizontal resolutions on simulation of 'MORA' tropical cyclone over Bay of Bengal using Numerical Weather Prediction Model

摘要

A numerical weather prediction model, Weather Research and Forecasting (WRF model) version 3.8 has been used to simulate a severe cyclonic storm "MORA" observed over Bay of Bengal (BoB) during 28-31 May, 2017. The initial simulation has been carried out over the region at 6-km horizontal resolution with 310 x 330 grid points in both north-south and east-west directions having 30 vertical levels. Initial conditions were used from National Centers for Environmental Prediction (NCEP) Final analysis (FNL) fields available at every 6 h at a spatial resolution of 1 degrees x 1 degrees. The model-simulated features of this event were evaluated against Indian Meteorological Department (IMD) data over the region. Sensitivity experiments were performed using six different microphysics schemes (Lin, Kessler, WSM3, Eta, WSM6 and Thompson) among which WSM3 scheme-simulated track was close to the observed IMD track. The model with WSM3 scheme has efficiently captured many important features in simulating the occurrence of the storm accompanied with wind speed, and sea level pressure, though there are some spatial and temporal biases in the simulation. After choosing the best microphysics scheme, we looked into the model performance in simulating the storm at different horizontal resolutions, 4 km and 9 km with 480 x 510 and 210 x 210 grid points, respectively. The results clearly revealed that cyclone track as well as other parameters related to the storm are sensible to horizontal resolution and has improved after finer resolution (i.e., 4 km) simulation.