Optimization of empirical typhoon model considering the difference of radius between pressure gradient and wind speed distributions

ABSTRACT This study proposes empirical relations for the ratio of the radius of maximum pressure gradient to the radius of maximum wind speed for the empirical typhoon model (ETM) based on the results of analysis of multiple typhoons obtained from the meteorological model. One proposed relation was parameterized based on the attenuation rate from the peak time to landfall time. The other was parameterized based on the distance from where the typhoon reached its peak intensity to the coastline. These relationships are useful for practical applications. In addition, the typhoon pressure shape parameter B was calculated from the constructed equations and the relational equation proposed by Holland. The improvement in accuracy, as compared with conventional ETM (B = 1, and B estimated by the gradient-wind equilibrium assumption), was determined for three cases of typhoons making landfall in Japan in recent years. As a result, it was confirmed that the proposed equations for parameter B are the most accurate amongst the three estimation methods. Accordingly, the improvement in the accuracy of the ETM using the estimation equations was validated. When using the ETM in the future, high accuracy can be realized by utilizing the estimation equations used in this study.