Abstract: The ETKF (Ensemble Transform Kalman Filter)DRY adaptive observation scheme can obtain the relative accurate sensitive region, but it hasn’t contained the humidity factor. This article is based on the ETKFDRY scheme developed by Ma (2008). According to the difference of the data and the metrics we constructed three different schemes, and compared with the old one. We choose the freezing disaster occurred in the early 2008 as an example. The results show that the sensitive area which is calculated by the old one is more scattered, and there are false sensitive areas when the verification time is equal to the adaptive observation time; with the adding of the humidity factor and the changing of the metrics the false sensitive areas have an apparent decrease; the ETKFWETE6 system which only contains the humidity factor has the best results, say, the sensitive areas are more concentrated at the adaptive observation time and there are no false sensitive areas when the verification time is equal to the adaptive observation time.