Identification and trend analysis of compound meteorological hazards along Vietnam’s coastline

The concept of compound hazards refers to the simultaneous occurrence or rapid succession of multiple hazards within a specific area. In this study, we identified compound meteorological hazards based on three types of individual hazards: high temperatures, heavy rainfall, and tropical cyclones (TCs). We computed the number of each type of individual hazards and their compounds at 10 selected stations along the coastline of Vietnam for the period 1980–2018. A temperature hazard (rainfall hazard) is identified if the maximum temperature (rainfall amount) on a given day exceeds the 95th percentile of all daily values recorded over the study period. A location is considered exposed to a TC hazard on a given day if the distance from that location to the TC center is less than 250 km. Subsequently, a compound hazard event is identified if the interval between the ending time of one individual hazard event and the starting time of the following one is less than 10 days. The results indicate that the annual number of compound hazards shows increasing trends at the majority of the stations, mainly due to the increase in temperature hazards. At the seasonal scale, compound hazards typically occur from March to November, primarily associated with temperature hazards in the first half of the year and with TCs and rainfall hazards in the later months. The identification and analysis of compound hazards in this study provide essential information for resilience and adaptation planning in Vietnam.