Sensitive Area Estimates Based On Etkf Adaptive Observation System Is Perfect And Its Preliminary Application Study

The Adaptive observation is one of the key issues of THORPEX to improve the accuracy of High Impact Weather (HIW) forecast. There are several approaches, which have been proposed in recent years, such as: SV(Palmer,1998); HSVs(Barkmeijer,1999); ET(Bishop,1999); ETKF(Bishop,2001) ;CNOP(Mu,2007), to determine the sensitive areas for adaptive observation. Based on the products of Ensemble Prediction System at NMC (National Meteorological Center) or other EPS resources, a similar ETKF (Ensemble Transform Kalman Filter) system has been established by Ma (2008) to determine the sensitive areas of HIW forecast in CMA.In this paper, we modified Ma's scheme of DRY-ETKF by taking the moist factor into account as a WET-ETKF. Two disaster HIW process were chosen for the case study: The extreme low temperature, heavy snowstorm disasters occurred in China in January of 2008, which led to huge losses to the Country; the typhoon"sinlaku"and"fengshen". The preliminary results showed that:The new system has a better result in calculating the sensitive areas: the sensitive areas which is calculated by the new system are more concentrate and the false sensitive areas had an apparent decrease.The experiment of sensitive areas indicated that the result of the new system is reasonable: In improving the initial field of sensitive areas which are calculated by the new system can reduce the error in the verification areas at the verification time.The humidity factor has a great contribute in calculating the sensitive areas, especially to the HIW which process depends on the humidity condition. The initial data can provide the information of the humidity and the guidance which contains the humidity factor can modify the distribution of the sensitive areas in a reasonable way.There must be different sensitive areas calculating system in dealing with the different HIW. The result calculated by this paper implicit that The EX6 system which only contains the moist factor had a better result in dealing with the extreme low temperature, heavy snowstorm disasters, however the ETKF-MZ2010 system is the best one when we consider the typhoon disaster.