Inhomogeneity detection in the precipitation series: case of arid province of Pakistan

Abstract

Reliable precipitation data are often required for conducting hydro-climatological assessments. Therefore, the study aims to detect the inhomogeneity in each calendar month, mean annual and monthly time series precipitation data of Balochistan, an arid province of Pakistan. The inhomogeneity was assessed using standard normal homogeneity test, Buishand range test, Pettitt test and von Neumann ratio test at 95% confidence level. The tests were applied over the precipitation data obtained from 14 meteorological stations for the period 1961–2009. The results of the different tests were classified as ‘useful’, ‘doubtful’ and ‘suspect’ based on the null hypothesis. The result of calendar months and annual series indicates that most of the data were ‘useful’. The output of monthly time series precipitation indicates that the data at Jiwani, Lasbela, Nokkunddi, Ormara, Pasni, Turbat and Zhob stations were ‘useful’ and others are classified into ‘doubtful’ and ‘suspect’ class. It was also observed that von Neumann ratio test is sensitive to minor changes in the precipitation data, and standard normal homogeneity test was found less sensitive to changes.