Assessing drought conditions through temporal pattern, spatial characteristic and operational accuracy indicated by SPI and SPEI: case analysis for Peninsular Malaysia

A strong understanding of severe drought conditions is important for its mitigation and damage alleviation. Given the Peninsular Malaysia’s drought vulnerability and its progressively increasing temperatures in the future, this study assessed the significance of temperature for the drought formation through temporal pattern, spatial characteristic and operational accuracy indicated by the Standardized Precipitation Index (SPI) and the Standardized Precipitation Evapotranspiration Index (SPEI) at the timescales of 1-, 3- and 6-month. Temporal analyses of drought frequency and fluctuations of the SPI and SPEI showed similar changes in moisture responsiveness over the increasing timescales. However, in terms of the number of dry months, the two indices showed different trends, consequential of the influence of temperature in the SPEI. The interchangeability of the two indices was confirmed through spatial variation analysis of drought frequency, mean drought duration, mean drought severity and mean drought peak. From an occurrence, duration and onset detection accuracy consideration, the SPI is better for the 1-month short-term drought, while the SPEI is better for the 3-month mid-term and 6-month long-term droughts. This is a result of the increased significance of temperature in drought formations. Further evaluations on drought severity also showed that the SPEI had better description of the long-term drought over Peninsular Malaysia during the 1997/1998 and 2015/2016 El-Nino drought events.