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Divergent Mechanisms of High Health-Risk Compound Hot and Dry Events across China's Early and Late Warm Seasons
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DOI：10.1175/JCLI-D-25-0366.1.png)
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Abstract
En 中文
Prolonged compound hot-dry events (CHDEs) have been linked to surging emergency medical demand, especially among vulnerable populations, making them a growing public health concern in a warming climate. However, the seasonal and regional drivers of high health-risk CHDEs (HHR-CHDEs) remain unclear, limiting effective public health responses. Here, we integrate a temperature-humidity-based health-risk index, ambulance dispatch records, and distributed lag nonlinear models to obtain high health-risk temperature-humidity thresholds. During HHR-CHDEs exposure, particularly higher emergency dispatch demands are observed among males, the elderly, and individuals suffering from trauma or alcohol poisoning. We further use ERA5 reanalysis data to examine the dominant modes and physical mechanisms of HHR-CHDEs across China during the early and late warm seasons. In the early warm season, HHR-CHDEs are concentrated in northwest China and are jointly driven by enhanced surface heating (51% contribution) and intensified moisture loss (37%), underpinned by the synergistic effect of an upstream Rossby wave source over eastern Europe and anomalous northwest Pacific sea surface temperature (SST) warming. This coupling promotes a quasi-stationary high pressure anomaly that blocks synoptic disturbances and reinforces regional heat-dryness feedbacks. By contrast, in the late warm season, HHR-CHDEs are centered over the middle-lower Yangtze River region and are dominated by persistent heat accumulation (65%) with a secondary drought contribution (25%). These events are driven by large-scale circulation anomalies resulting from upstream Rossby wave energy originating in the North Atlantic and enhanced by downstream SST warming over the subtropical northwest Pacific. This Atlantic-Pacific coupling induces pronounced adjustments in the Walker and Hadley circulations, promoting subsidence and suppressed monsoonal moisture transport, and sustaining a health-threatening hot-dry atmosphere over densely populated regions. These findings reveal seasonally distinct remote forcing pathways and highlight the value of integrating large-scale diagnostics into climate-health early warning systems. SIGNIFICANCE STATEMENT: High health-risk compound hot-dry events (HHR-CHDEs) are a growing climate-health threat, yet their physical drivers remain poorly understood. This study identifies seasonally distinct large-scale atmospheric and oceanic precursors of HHR-CHDEs across China, revealing key Rossby wave pathways and land-atmosphere feedbacks that amplify these events. By integrating climate diagnostics with health-relevant thresholds, our findings bridge the gap between meteorological extremes and public health outcomes, offering a foundation for targeted early warning systems under climate change.
Keywords:
Atmosphere-land interaction
Health impacts
Extreme events
Air-sea interaction
Journal
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4
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1.4W
Citations:
5.9W
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