Spatio-Temporal Variations and El Niño Modulation of Meteorological Droughts in Malaysia

Meteorological droughts in Malaysia have significantly impacted critical sectors such as agriculture, water resources, health, the environment, tourism and various socio-economic sectors, affecting the population's livelihood and well-being. This study analyses drought characteristics over a 39-year period, from 1982 to 2021, using the Standardised Precipitation Index (SPI) derived from 5-km resolution Climate Hazards Group InfraRed Precipitation with Station data (CHIRPS). The droughts were assessed on 3-, 6-, 9- and 12-month timescales to investigate spatio-temporal variations in characteristics such as frequency, duration, peak, severity and intensity. The study also provides an in-depth analysis of large-scale drought modulation, particularly associated with the El Niño phenomenon and its teleconnection in the Maritime Continent. Depending on the location and timescale, the number of meteorological drought occurrences varied from 10 to 22 for the 3-month timescale and 4 to 14 for the 12-month timescale. Generally, as the timescale of a drought increases, the peak intensity decreases, while the duration and severity increase. Additionally, drought intensity decreases over longer timescales. These characteristics show significant spatial variations. Results indicate that meteorological droughts in Malaysia were almost entirely modulated by the El Niño phenomenon through its induced teleconnection over the Maritime Continent. Drought characteristics exhibit a strong seasonality linked to changes in the Walker circulation and the strengthening and weakening of anticyclonic circulations associated with Rossby waves induced by heating in the Pacific Ocean. Very strong El Niño events had the most significant influence on the droughts. The positive Indian Ocean Dipole (pIOD) strengthened the effects of El Niño but it itself had no significant influence on the droughts. In most regions, there were no significant trends in the characteristics of meteorological droughts. However, in northeast Peninsular Malaysia and some scattered areas along the west coast of the peninsula, significant trends are observed in peak, duration and severity.