Homogeneity Test on Daily Rainfall Series for Malaysia

Abstract

In this study, homogeneity tests have been applied at 76 meteorological stations in Peninsular Malaysia from 1975 to 2010 and also 7 stations in Sabah and Sarawak. A twostep approach is followed. First, four homogeneity tests, namely standard normal homogeneity test (SNHT), Buishand range test, Pettittt test, and von Neumann ratio tests are applied to evaluate the daily series. In order to evaluate the performance of the methods used, two testing variables i.e. annual rainfall amount and annual number of wet days with threshold 1mm are selected. After that, the results of the different tests are classified into three classes: ‘useful’, ‘doubtful’ and ‘suspect’. Each test is evaluated separately and inhomogeneous stations are determined. By considering both of the testing variables, the result shows that 22% of the station series in Peninsular Malaysia are detected as inhomogeneous series and the remaining 59 stations which are equivalent to 78% are considered homogeneous. Meanwhile, for Sabah and Sarawak all stations or 100% are classified into homogenous series. Keywords: Homogeneity Tests; Standard Normal Homogeneity Test; Buishand Range Test; Pettitt Test; Von Neumann Ratio Test; Rainfall Amount Series; Wet Day Series. 2010 Mathematics Subject Classification: 62P12