Spatial Distribution and Trends of Heat Stress in Vietnam

Abstract

This study investigates the spatial distribution and trend of heat stress in Vietnam using data from 68 meteorological stations across the country’s seven climatic sub-regions between 1979 and 2018. Daily maximum wet-bulb temperature (TWmax), an indicator of heat stress, was computed based on the daily maximum air temperature (Tx) and relative humidity at 13:00 LST (RH13). Results indicate a strong positive correlation (>0.97) between daily TWmax and Tx and a weaker relationship between daily TWmax and RH13. Tx and TWmax experienced a general increasing trend across most stations over the study period, while RH13 displayed both negative and positive trends. Vietnam’s heat stress thresholds were found to be higher than those in many other parts of the world due to the country’s location and its temperature-humidity conditions. The study identifies most parts of Vietnam have experienced an increase in heat stress days, typically ranging from 5 to 12 days per decade. Among the four seasons, summer contributed the most (50-80%) to the annual number of heat stress days in most sub-regions, except for the Central Highlands and the South where spring had the highest contribution (65-80%). Overall, this study provides useful benchmark values for future research on heat stress in Vietnam.