A typhoon initialization scheme based on incremental analysis updates technology

The main difficulty in typhoon initialization lies in how to generate variables that are consistent with the prescribed wind field based on limited observational data (such as the location of typhoon center,the minimum pressure,the maximum wind speed,and the size of typhoon). In this study,the IAU (Incremental Analysis Updates) is introduced into typhoon initialization scheme to solve this problem. The background vortex perturbation is relocated and adjusted first according to observations,other variables are then generated by the model through a strong 6 h nudging to the prescribed wind field. Multiple forecast experiments for typhoon Mangkhut indicate that:(1) The influence of typhoon initialization proposed in the present study on the track forecast is weak,while the forecast of intensity is significantly improved. Especially in the generation stage,the intensity of the typhoon is strengthened after initialization process and becomes more consistent with observation. (2) The IAU technology can make adjustment on other variables according to the prescribed wind field,and produce a more thermally and dynamically consistent vortex structure. The forecast of typhoon track and intensity is further improved after the IAU technology is implemented. (3) Sensitive experiments indicate that the relaxing time of 3-6 h can yield the best result.