206 / 2024-02-27 18:25:33

Homogeneity and trends of precipitation in the Peninsular Malaysia East Coast using National Hydrological Network datasets

Precipitation,Homogeneity,Trend,Peninsular Malaysia,Standard Precipitation Index

Long-term precipitation records are essential in the development of the water resources model to ensure its ability to consider climate variability. Satellite products are believed to have inherited a certain degree of inaccuracy, resulting in a preference for ground-based gauges to obtain the datasets. However, these gauges always suffer from uncertain records caused by the replacement of equipment, instrument calibration, and malfunctioning gauges, which, at worst, leads to misrecords of the particular precipitation events. This is causing a problem in the hydrological model development and hydroclimatic analysis since the quality check of the involved stations is time-consuming due to its complexity, and in most cases, it is not being conducted. The study is conducted to identify reliable stations that can be referred for any future hydrological and hydroclimatic analysis within the East Coast of Peninsular Malaysia. This region is particularly vulnerable to the climate disaster on account of its exposed location, which directly faces the South China Sea. Infilling of missing daily precipitation datasets was carried out using the Thiessen polygon technique in order to sequentially complete the long-term records. Via four established homogeneity tests: Alexandersson’s standard normal homogeneity test, Buishand’s test, Pettitt’s test, and the von Neumann ratio test, all precipitation gauges registered under the Malaysia National Hydrological Network are reviewed and checked, annually and seasonally for 50 years from 1973 to 2022. It was found that 73 and 125 out of 232 stations were inhomogeneous at the 1% and 5% significance levels, hence being eliminated prior to in-depth precipitation analysis.  The homogenous gauges are then referred to examine the temporal trends based on the Mann-Kendall trend test with Sen’s slope approach to identify the changes in magnitude. The trend test shows that most areas are dominated by positive trends over the years, except for the southwest monsoon. Lastly, the historical spatiotemporal precipitation over the study area in the past years is observed using the Standard Precipitation Index, also known as SPI, to measure the historical magnitude of wet and dry conditions.