This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: 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.
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