Threshold selection for extracting extreme rainfall using data from northern region Peninsular Malaysia

This study is aimed to extract extreme rainfall data using Peak over Threshold (POT) method. The method would be used in conjunction with the generalized Pareto distribution (GPD) model. Daily rainfall data in the northern region of Peninsular Malaysia obtained from the Department of Irrigation and Drainage Malaysia (DID) for the period 1999 to 2019 is used. The mean residual life plot and parameter stability plot are used to choose a suitable threshold. The problem of choosing a suitable threshold for the extraction of extreme rainfall data is addressed by comparing the threshold to the constant threshold and the marginal threshold. The Maximum Likelihood Estimator (MLE) is used to estimate the parameters. Diagnostic plots and the return level are determined to confirm the suitability of the adapted model. According to the analysis, the selected constant threshold is 42 mm and the selected marginal threshold for all stations are varies from 38 mm to 48 mm. Generally, the maximum daily rainfall at all stations increases steadily during a higher return period. Over the next 25 years, the maximum daily rainfall amount is expected to return to all stations.