Typhoon initialization in the CMA global forecast system

A global model typhoon initialization scheme is developed based on the global four-dimensional variational data assimilation (4DVar) of CMA global forecast system (CMA-GFS) with reference to the BDA (Bogus Data Assimilation) method. The scheme assimilates 1 h interval information of typhoon center location and central sea level pressure diagnosed by interpolation method, and generates typhoon circulation using the model dynamic physical constraints within the 4DVar assimilation window. At the same time, errors in the central sea surface pressure are dynamically corrected using a technique that takes into account the model's ability to describe typhoon circulation. Experiments of 22 typhoon cases that occurred in the Northwest Pacific in 2016 show that the new scheme not only promotes the generation of typhoon circulation in the initial field, but also significantly reduces errors in the mean typhoon track and intensity predicted by the CMA global forecast system. Therefore, this scheme has a potential for operational application.