Performance Evaluation of GPU-Based WRF Model in Simulating a Unique Tropical Cyclone of Arabian Sea: A Case Study of VSCS Vayu

Mukherjee, Pubali ; Ramakrishnan, Balaji

Abstract

Tropical cyclone (TC) Vayu developed from a low-pressure system on 9 June 2019 near the West coast of India. Itunderwent rapid intensification (RI) to a very severe cyclonic storm (VSCS) before weakening into a deep depression on 17June 2019 with a unique track. The present study aims to evaluate the performance of the GPU-WRF model in simulatingthe unique tropical cyclone Vayu when initialized with different meteorological boundary conditions and the effect of inputof time-varying SST data, the track, and the cyclone's intensity. The study also aims to investigate the cyclone's synopticparameters during its development and intensification. Four simulations are conducted with GFS and NCEP-FNL data withand without SST input. The four-dimensional data assimilation analysis technique, the fdda analysis nudging scheme, wasused on the GFS data with SST input, which showed a significant improvement in track and intensity. The system skirtingthe Gujrat coastline on 13 June is skillfully captured. Given the appreciable improvement of track and intensity with GFSdata using nudging, further investigation of the cyclone's synoptic parameters is done on the same. Overall, comparing thesimulated dynamics with the ERA-5 dataset indicated that the model simulated a stronger TC. WRF can skillfully simulate awell-delineated eye wall at the matured stage (wind speed >40 m/s). An anomalously high mid-tropospheric relativehumidity (RH) (~90%) is indicated at the developing stage, indicating the onset of RI, during which the system showed RH~100% at the mid-troposphere. On 14 June, when the system reached VSCS, the simulated storm's low-level relativevorticity was ~359.93 × 10 –5 s-1, whereas ERA-5's was ~175.39 × 10 –5 s-1 only. The simulated storm cyclone energy(9.35×104 knts2) was lower than the observed (11.54 ×104 knts2). The significance of the results obtained from the study isthat the model can skillfully simulate the track and intensity of an Arabian Sea TC and capture TC Vayu's cyclogenesis. Thestudy also provides insight into the cyclone's synoptic parameters, such as mid-tropospheric relative humidity, low-levelrelative vorticity, and cyclone energy, during its development and intensification. The study's findings can be useful inimproving the accuracy of tropical cyclone forecasting and enhancing our understanding of the physical processes involvedin their formation and intensification for the Arabian Sea region.

Keyword(s)

WRF; GFS; NCEP; SST; Nudging; Cyclone Vayu; GPP

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