The Inhomogeneity Test Method of Atmospheric Pressure Sequences Based on Γ-distribution

Climate change research is built on the basis of homogeneity sequence data which can reflect the real changes. Therefore the homogeneity and/or the inhomogeneity of the meteorological observation data should be tested before using the data for climate change research. Currently, the main methods of homogeneity test are based on the hypothesis that the data sequences obey the normal distribution. However, in Anhui Province, it is found the average pressure sequence homogeneity test for 23 representative stations from 1961 to 2006 that some sequences are not subject to normal distribution, which can not be tested by the common method based on normal distribution. At the same time, it is found that some sequences obey Γ-distribution (pass the significant level of 0.05 Kolmogorov goodness of fit tests). A new homogeneity test method, Γ-test, for atmospheric pressure sequences is presented, in which the hypothesis should be met at first that the sequence is subject to Γ-distribution. Firstly, some reference stations are used to construct a reference sequence; then the ration sequences of stations which will be the test sequences to reference sequences are gotten; thirdly, the ration sequences are tested by Γ-test sequence homogeneity test; finally, the cause of the inhomogeneity sequences are analyzed by checking the history of the stations.The method is briefly introduced, and the data of Tongcheng are taken as an example, the concrete process of Γ-testing and analysis are given. Furthermore, the result of Γ-test is compared with SNHT which is a widely use method. The results show that the 23 stations can be tested by Γ-test and the accuracy rate reaches 78.3%. In contrast, four stations can not be tested by SNHT and the accuracy only reaches 53.8%. In other words, Γ-test is superior to SNHT in scope and accuracy. Nevertheless, Γ-test also has some problems such as the high computational complexity and missing of some change points. The Homogeneity test results show that the change of barometer height and the station location is the main reason of the significant inhomogeneity of atmospheric pressure sequences in An hui Province.