This study aimed to analyze the spatiotemporal changes of historical droughts over the Muda River basin (MRB), Malaysia, from 1985 to 2019 using the Standardized Precipitation Index (SPI) and the Standardized Streamflow Index (SSI). The Mann–Kendall test and Sens’ slope were used to evaluate the trends and magnitude changes in the droughts, respectively, while Spearman’s rho was applied to understand the relationships of the droughts with large-scale atmospheric circulations, such as the El Niño Southern Oscillation (ENSO), the Indian Ocean Dipole (IOD), and the Madden–Julian Oscillation (MJO). The results show that the intense droughts in the MRB mostly occurred in 1991–1992, 1995, 1998, 2002–2003, 2005–2006, 2008, 2012–2013, and 2016. In addition, a declining SPI trend was found from May to December at most of the stations. About 80% of the stations experienced about 10 severely dry droughts, while almost all stations experienced at least 5 extremely dry events. Moreover, a higher response rate of the SSI than the SPI was found during low-rainfall months from January to May. Lastly, ENSO had a larger impact on the drought formations over the MRB compared to the IOD and MJO, especially during the dry period.

中文翻译：

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1985-2019年马来西亚慕达河流域干旱变化特征

本研究旨在使用标准化降水指数 (SPI) 和标准化流量指数 (SSI) 分析 1985 年至 2019 年马来西亚穆达河流域 (MRB) 历史干旱的时空变化。Mann-Kendall 检验和 Sens 斜率分别用于评估干旱的趋势和幅度变化，而 Spearman 的 rho 用于了解干旱与大尺度大气环流的关系，例如厄尔尼诺南方涛动(ENSO)、印度洋偶极子 (IOD) 和马登-朱利安振荡 (MJO)。结果表明，MRB的严重干旱主要发生在1991-1992年、1995年、1998年、2002-2003年、2005-2006年、2008年、2012-2013年和2016年。此外，5-5月SPI呈下降趋势12 月在大多数车站。大约 80% 的站点经历了大约 10 次严重干旱，而几乎所有站点都经历了至少 5 次极端干旱事件。此外，在 1 月至 5 月的低降雨月份期间，SSI 的响应率高于 SPI。最后，与 IOD 和 MJO 相比，ENSO 对 MRB 干旱形成的影响更大，尤其是在干旱时期。