The Research Progress of the Typhoon Targeted Observations Based on CNOP Method

This paper briefly yet systematically introduces the research progress of the application of conditional nonlinear optimal perturbation (CNOP) to typhoon targeted observations. The CNOP is an extension of the singular vector (SV) into the nonlinear region. It has been used to identify sensitive areas in typhoon targeted observations. Assimilation observations in this area are hoped to improve the typhoon forecast largely and this area is called sensitive area in this sense. The theoretic basis of the application of CNOP to typhoon observation is first reviewed. Then the impact of the model resolution, the verification area design and the optimization time period on the CNOP-identified sensitive areas are described. The effectiveness of the CNOP-identified sensitive areas is examined by observation system simulation experiments (OSSE) and observation system experiments (OSE). Finally, the prospect of the application of CNOP method to the operational targeted observations and its further application are discussed and summarized.