New study reveals where drought and extreme heat converge across Oman

New study reveals where drought and extreme heat converge across Oman Sadie Harley Scientific Editor Andrew Zinin Chief Editor Drought and extreme heat do not always occur separately. When they coincide, their combined effects can place greater pressure on water resources, agriculture, ecosystems, energy systems and public health. A new study by researchers at Sultan Qaboos University and the Environment Authority of Oman examined where and how compound drought–heat wave events have occurred across Oman. A key finding is that the areas most affected by either hazard individually are not necessarily those most exposed to their combined occurrence. The researchers analyzed ERA5-Land climate data covering 1950–2024 to assess the frequency, duration and severity of droughts, heat waves and events in which both occurred at the same time. Drought conditions were measured using the Standardized Precipitation Evapotranspiration Index (SPEI), which considers both precipitation and atmospheric water demand. Heat waves were identified using relative temperature thresholds, allowing unusually hot conditions to be assessed in relation to the normal climate of each location. The article, "Assessing compound drought-heatwave events in Oman using non-stationary copula models," was published in Journal of Hydrology. The findings show that drought and heat wave risks were distributed differently across Oman. The interior and western parts of the country experienced the highest incidence of drought, while heat waves were more prominent along the northern and northeastern coasts. Compound drought–heat wave events occurred most frequently in central-western and northern regions. The years 2023–2024 stood out for exceptional compound-event severity within the analyzed historical record. Long-term trend analysis revealed statistically significant increases in drought frequency across approximately 60.32% of the analyzed grid cells. In contrast, heat wave and compound-event trends were more geographically heterogeneous, underscoring that different climate hazards do not necessarily change in the same way. To examine how the relationship between drought and heat waves may change over time, the team used non-stationary copula models. Unlike conventional stationary models, these approaches can represent changing statistical relationships between hazards. The researchers compared Gaussian and Clayton copula models and evaluated their performance using the Akaike Information Criterion. A model allowing both location and scale parameters to vary provided the best fit, highlighting the value of accounting for non-stationarity when assessing compound extremes. The analysis identified stronger dependencies between drought and heat waves in coastal areas. Modeled joint probability values reached up to 87% in parts of the southern and eastern coasts, while the estimated strength of dependence varied considerably across the country. The 87% figure is a joint probability estimated under the study's statistical definitions and modeling framework; it is not an 87% forecast of a drought–heat wave event in any particular future year. These findings illustrate why drought and heat waves should not always be assessed as separate hazards. A region may not have the highest incidence of either hazard individually but may still experience substantial exposure when dry and exceptionally hot conditions occur together. Mapping these regional differences could support locally targeted water management, agricultural planning, ecosystem protection, heat preparedness and climate-risk assessment. Beyond Oman, the study offers a transferable analytical framework for investigating compound climate extremes in other arid and semiarid regions, where water scarcity and extreme temperatures pose major environmental and socioeconomic challenges. The study analyzed historical climate patterns and statistical dependencies; it did not forecast events in particular future years or directly attribute observed events to human-caused climate change. Further research with climate projections, independent datasets and impact information would help assess future risks. "Our findings demonstrate that drought and heat waves cannot always be evaluated independently. Regions experiencing the most severe individual climate hazards are not necessarily those facing the greatest compound risks. Understanding these evolving relationships is essential for developing more effective and region-specific climate adaptation strategies," said Dr. Mohammad Reza Nikoo, corresponding author, Sultan Qaboos University The research team comprised Malik Al-Wardy and Erfan Zarei (Center for Environmental Studies and Research, Sultan Qaboos University), Mohammad Reza Nikoo (Department of Civil and Architectural Engineering, Sultan Qaboos University; corresponding author), and Maha Al-Balushi (Department of Climate Mitigation, Environment Authority, Oman). More information Malik Al-Wardy et al., Assessing compound drought-heatwave events in Oman using non-stationary copula models, Journal of Hydrology (2026). DOI: 10.1016/j.jhydrol.2026.136149 Provided by Sultan Qaboos University