Application of Pettit and Buishand tests to quality control of annual rainfall data of Chaharmahal and Bakhtiari, and Khuzestan provinces

It is necessary to collect rainfall data for hydrological and hydrometeorological studies. To prepare this data, it is necessary to observe and record it at meteorological stations. In the process of determining rainfall amounts using rain gauges, various types of errors can occur. Therefore, some errors may be introduced into the final data during the observation and recording process. As a result, quality control of rain gauge data is of utmost importance. The objective of this study was to investigate the homogeneity of annual rainfall data at 61 rain gauge stations in the province of Chaharmahal and Bakhtiari and at 82 rain gauge stations in the province of Khuzestan. To detect the heterogeneity of the data, Pettit and Buishand's non-parametric tests were compared. The results indicated that, according to the Pettit test, the data of seven stations in Chaharmahal and Bakhtiari, and 24 stations in Khuzestan provinces are heterogeneous among the investigated stations. According to the Buishand test, there were significant differences in rainfall data among the three stations in Khuzestan province. Consequently, the data appears to be heterogeneous. It should be noted that even though both of these tests are used to test the homogeneity of rainfall data, the Pettit test involves two hypotheses with different continuous distributions. The Pettit test is considered more reliable in detecting homogeneity in comparison to the Buishand test in the study stations.