Sensitivity analysis of the physics options in the Weather Research and Forecasting model for typhoon forecasting in Japan and its impacts on storm surge simulations

Weather Research and Forecasting (WRF) model is useful for forecasting typhoons as an external force of storm surge forecasts. This study examines the variation in typhoon forecasts caused by different choices of arbitrary physics options in WRF and their influence on storm surge forecasts. Eight frequently used combinations of cloud microphysics and planetary boundary layers were extracted via a review of previous studies. Subsequently, sensitivity analyses of these physics options were performed, targeting nine typhoons that landed in Japan during 2015–2019. Additionally, we conducted case studies of storm surge ensemble forecasts in Tokyo Bay and Osaka Bay using WRF-simulated typhoons generated in the sensitivity analysis. As a result, the ensemble mean of the forecasts was comparable to the storm surge reanalysis simulation results obtained using an empirical typhoon model wherein the best track data is integrated to reproduce atmospheric fields. This may be attributed to the fact that the typhoon parameters (intensity, size, approaching angle, and velocity) obtained from the best track at landfall were generally within the range of the parameters that were simulated using WRF.Published versionThis research was conducted as part of the Earth Simulator application project “Superimposed Disasters of Heavy Rainfall, Storm Surge and Tsunami” (Research director: T. Arikawa) of the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) and utilized the computing resources of the Earth Simulator. The work was also supported by “Collaborative Research Project on Computer Science with High-Performance Computing in Nagoya University”