Spatiotemporal characteristics of hydro-meteorological droughts and their connections to large-scale atmospheric circulations in the Kelantan River Basin, Malaysia

Climate change exacerbates dry seasons in Southeast Asia, leading to water supply shortage for agricultural use. However, the link between hydro-meteorological droughts and large-scale atmospheric circulations, such as the El Nino Southern Oscillation (ENSO), Indian Ocean Dipole (IOD), and Madden–Julian oscillation (MJO), has received very little attention. Therefore, this study aims to analyse the hydro-meteorological droughts that occurred in the Kelantan River Basin (KRB) between 1985 and 2020 using the Standardized Precipitation Index (SPI) and Standardized Streamflow Index (SSI) as well as their connections to ENSO, IOD, and MJO. Sens’ slope and Mann–Kendall test were employed to evaluate the trends and magnitude changes of the historical droughts, respectively. In addition, the response rate of SSI to SPI was considered to understand how precipitation affects streamflow. The results show that extremely dry events occurred in 1986, 1987, 1989, 1990, 1992, 1997–1998, 2015–2016, and 2020. Based on the SSI results, more than 70% of extremely dry periods last 6 months or longer. Interestingly, from January to May, when there was low precipitation, SSI had a higher response rate to SPI. The ENSO, as opposed to the IOD and MJO, had a stronger impact on the dry conditions over the KRB.