Homogeneity Test on Daily Rainfall Series for Malaysia

In this study, homogeneity tests have been applied at 76 meteorological stations inPeninsular Malaysia from 1975 to 2010 and also 7 stations in Sabah and Sarawak. A twostepapproach is followed. First, four homogeneity tests, namely standard normalhomogeneity test (SNHT), Buishand range test, Pettittt test, and von Neumann ratio tests areapplied to evaluate the daily series. In order to evaluate the performance of the methodsused, two testing variables i.e. annual rainfall amount and annual number of wet days withthreshold 1mm are selected. After that, the results of the different tests are classified intothree classes: ‘useful’, ‘doubtful’ and ‘suspect’. Each test is evaluated separately andinhomogeneous stations are determined. By considering both of the testing variables, theresult shows that 22% of the station series in Peninsular Malaysia are detected asinhomogeneous series and the remaining 59 stations which are equivalent to 78% areconsidered homogeneous. Meanwhile, for Sabah and Sarawak all stations or 100% areclassified into homogenous series.