Sensitivity experiments of tropical cyclone track and intensity on SST: WRF simulations with bogus vortex

Abstract:

Effects of sea surface temperature on WRF (Weather Research and Forecasting model) tropical cyclone (TC) forecasts were investigated to figure out an optimal humidity profile of the bogus vortex. For this purpose, sensitivity of relative humidity (RH) of the bogus vortex on the initial sea surface temperature (SST) and surface heat fluxes was analyzed through WRF TC simulations for both ideal and real TC cases. For both cases, the SABV (Structure Adjustable Balanced Vortex) consisting of three-dimensional empirical functions for surface pressure, geopotential, temperature, tangential- and radial wind was used as an initial bogus vortex. Based on the sensitivity experiments, the humidity profile of the bogus vortex used as TC initial field was modified and then applied to the WRF TC forecasts for the Typhoons from 2017 to 2019. Effect of SST on the track and intensity forecasts with focus on the temporal resolution (6 hourly or daily) was also examined, where different data set of SST provided by FNL and ERA5 were compared. Forecast experiments with the modified bogus vortex based on the sensitivity tests showed an improvement, particularly for the track prediction. Forecast performance using different data set of SST, however, did not show a significant difference between them, although the forecasts with the FNL data exhibited a slight better results over the ERA5 SST for some cases.