Research report: Meteorological drought characteristics in the South Central region of Vietnam based on SPI and SPEI indices in the period 1984–2023

Meteorological drought in Vietnam’s South Central region became markedly more severe during the final decade of a 40-year index analysis, with reduced rainfall and rising temperatures associated with more severe conditions in southern provinces. The study examined drought from 1984 through 2023 using the Standardized Precipitation Index (SPI) and Standardized Precipitation Evapotranspiration Index (SPEI), both calculated over a three-month timescale. It found that drought frequency declined during the middle decades as rainfall increased, then rose again in the last decade, particularly in the south.

The analysis combined Climate Hazards Center InfraRed Precipitation with Station (CHIRPS) rainfall data and potential evapotranspiration estimates from the Global Land Evaporation Amsterdam Model, or GLEAM. SPI and SPEI produced broadly similar spatial and temporal patterns of drought occurrence, although SPEI generally generated lower values. The study interprets this difference as evidence that potential evapotranspiration contributed to enhanced drought severity.

Its results therefore associate potential evapotranspiration not only with changes in drought frequency but also with the intensification of estimated meteorological drought under conditions of increasing temperature and decreasing rainfall. Drought patterns varied strongly across space and season. Southern provinces were characterized by longer dry seasons, lower rainfall amounts and more negative rainfall–potential evapotranspiration differences than northern provinces.

Potential evapotranspiration itself showed relatively weak spatial and seasonal variability across the region. Both indices recorded fewer drought events and a lower average number of drought months during the two middle decades of the study period, a pattern associated with increased rainfall. That change was not sustained in the final decade: drought events and the average number of drought months increased again in southern provinces as rainfall declined and temperatures rose.

Severity increased most clearly when drought was evaluated with SPEI, whose lower values showed the added influence of potential evapotranspiration. The longest drought durations also increased significantly in the southern provinces, pointing to longer-lasting dry episodes in that part of the region. Even with those limits, the results identify a geographically uneven pattern: drought was less frequent during two wetter middle decades but returned and intensified in southern provinces during the most recent decade, with SPEI indicating a particularly clear escalation in estimated severity.

The authors say the findings can contribute to drought monitoring, water-resource risk assessment and climate-adaptation planning in the region.

Subject of Research: Spatiotemporal characteristics of meteorological drought in South Central Vietnam from 1984 to 2023 using SPI and SPEI

Article Title: Meteorological drought characteristics in the South Central region of Vietnam based on SPI and SPEI indices in the period 1984–2023

Article References: Nguyen-Quoc, B., Nguyen-Minh, T., Vu-Thanh, H., & Pham-Thanh, H. (2026). Meteorological drought characteristics in the South Central region of Vietnam based on SPI and SPEI indices in the period 1984–2023. Theoretical and Applied Climatology, 157(11), Article 736. https://doi.org/10.1007/s00704-026-06672-3

Image Credits: AI Generated

DOI: 10.1007/s00704-026-06672-3

Keywords: meteorological drought, South Central Vietnam, SPI, SPEI, potential evapotranspiration, CHIRPS rainfall, drought severity, climate adaptation, Meteorological, drought, characteristics, South