Spatiotemporal variability assessment and accuracy evaluation of Standardized Precipitation Index and Standardized Precipitation Evapotranspiration Index in Malaysia

Drought indices like Standardized Precipitation Index (SPI) and Standardized Precipitation Evapotranspiration Index (SPEI) are applied to determine the drought occurrence. The drought characteristics are quantified based on the frequency, duration, peak and severity. The application of the two drought indices may provide different accuracy and indication on the drought characteristics. Thus, it is necessary to determine the better drought index for an accurate drought assessment in water resources planning and management. This study assessed the spatiotemporal variation of the drought characteristics in Malaysia based on SPI and SPEI. Furthermore, the novelty of this study is to evaluate the accuracy SPI and SPEI for the historical drought formation under the influence of rainfall and potential evapotranspiration trends. The temporal analysis results indicated the reducing dry conditions for both drought indices except the inland part of East Coast region for Peninsular Malaysia. Additionally, the spatial analysis results showed a higher drought frequency but shorter duration and less severe at the inland part of East Coast Region for Peninsular Malaysia and Northern region of East Malaysia for 1-month and 3-months time scales. Besides, there were lower occurrences of 6-months and 12-months drought with the overall increase in the rainfall trend in Malaysia. For the evaluation of accuracy, the SPEI was deemed more accurate as compared to SPI by achieving a higher true positive rate and negative predictive rate, lower false detection rate, false negative rate, and onset detection. The SPEI also provided a better description of the most severe drought events in year 1997/1998 and year 2015/2016. The outcomes are useful to develop mitigation strategies against the climate change.