Spatiotemporal analysis of seasonal SPEI in Peninsular Malaysia

Precipitation prevails in Peninsular Malaysia throughout the year. However, the extremity and inconsistencies in the pattern and intensity of precipitation also subject Malaysia vulnerable to droughts and dry spells. There are two main factors affecting the climate pattern in Peninsular Malaysia, namely the Northeast Monsoon and the Southwest Monsoon. Therefore, it is important to monitor the climate pattern in these periods to offer better drought prediction in Peninsular Malaysia. The Standardized Precipitation Evapotranspiration Index (SPEI), an index that considers both precipitation and temperature variables was adopted in the study. Seasonal SPEIs were built for the periods of the Northeast Monsoon (SPEI-NEM), the first inter-monsoon (SPEI-Inter1), the Southwest Monsoon (SPEI-SWM) and the second inter-monsoon (SPEI-Inter2) to represent the drought severity during these four periods. 133 precipitation and 28 temperature stations with availability of data from year 1983 to 2017 (35 years) were used to construct the seasonal SPEIs for whole Peninsular Malaysia. The number of dry seasons identified by the indices were first been tested to investigate the linear trend of seasonal drought occurrence in each region. Then, severity represented by the indices were spatially interpolated over Peninsular Malaysia to produce an overview of the changes of moisture condition over distance. Trend analyses using the Mann-Kendall trend test and the Sen's Slope were also carried out on the drought index series. The results showed that the occurrence of seasonal droughts had increase throughout the years investigated. The spatial interpolation of drought severities also showed dissimilar variation among the seasons but justifiable on the premise of climatic change caused by monsoon winds and the topography of the study area. Thereafter, the spatial analysis of seasonal drought trend has also been carried out where the SWM season was found to be the most drought vulnerable season in the future, with the Southern region being the most vulnerable as its trend tests showed increasing drought trend regardless of the season period. These suggest that the water resources planning in the future should focus more on the two mentioned aspects for sustainable water supply.