Multi-Test Homogeneity Assessment of Long-Term Rainfall Series in Peninsular Malaysia

Abstract

The primary goal of this study is to analyse the homogeneity of rainfall in Peninsular Malaysia, crucial for understanding climate change impacts and water resource management. Despite the importance of rainfall data for hydrological and engineering applications, inconsistencies and inhomogeneities in long-term rainfall records can lead to misleading conclusions about climate trends and compromise infrastructure design. In Peninsular Malaysia, limited studies have systematically assessed rainfall data homogeneity, leaving uncertainty about the reliability of existing datasets. Given the rising implications of climate change, assessing the consistency and potential changes in rainfall patterns is essential for effective infrastructure and resource planning. Using rainfall data collected over a 21-year period (1998–2018) from 10 meteorological stations, the study employs various statistical methods, including the Von Neumann Ratio Test, Pettitt Test, Buishand Range Test, and Standard Normal Homogeneity Test, to evaluate temporal and spatial uniformity in rainfall patterns. Rainfall stations are categorised as 'useful', 'suspect', or 'doubtful' based on the results. 'Useful' stations show consistent and reliable data, while 'suspect' and 'doubtful' stations indicate potential inconsistencies. The findings in this study are Petaling Jaya in annual and Alor Setar in May were flagged as suspect, while Subang in May, Melaka in annual, Kuala Terengganu in August, and Bayan Lepas in January were considered doubtful. The remaining stations and time series exhibited consistent and reliable patterns. Additionally, the Sequential Mann-Kendall Test is used to detect trends and shifts in the data. The findings offer crucial insights into the homogeneity of rainfall distribution across Peninsular Malaysia, highlighting discrepancies that could impact water resource planning and climate change adaptation strategies. This research is valuable for engineers, researchers, and stakeholders involved in sustainable water resource management and infrastructure development, providing empirical evidence for hydrology and climate studies.