Abstract:
This study analyzes rainfall variability and its links to ENSO phenomena in Ho Chi Minh City using data from Nha Be station (1999–2024). Results show that rainfall is highly concentrated in the wet season (May-November), with 84% of the annual total, while the remaining 16% occurs during the dry season (December-April). Despite high monthly and interannual fluctuations, annual totals remain relatively stable (mean 1683 mm, CV = 20.7%). Trend analysis using the Mann-Kendall test and Sen’s Slope indicates no significant trend, except for an increasing trend in September (6.2 cm/year, P = 0.052). Empirical Mode Decomposition (EMD) reveals multi-scale rainfall oscillations. IMF6-IMF8, corresponding to 1.7–6.5 years, are linked to ENSO signals. A composite IMF678 shows a significant inverse correlation with the Oceanic Niño Index (R = -0.361, lag = 7 months), indicating that El Niño reduces rainfall by 81.6 mm, while La Niña increases it by 51.8 mm. Extreme rainfall indices R25mm and R99p show strong interannual variability and tend to increase during La Niña years (1999–2000, 2010–2012, 2017–2018) and decrease during El Niño years (2002–2003, 2014–2015). However, some exceptions (2009–2010) indicate additional influences from regional factors.