Unprecedented late-summer mega-heatwave over the Yangtze River Basin in 2024: dynamical fingerprint of extreme anomalous atmospheric circulation variability
- 1Yunnan Natural Hazards Prevention Center/Climate Change and Resource Utilization in Complex Terrain Regions Key Laboratory of Sichuan Province, School of Atmospheric Sciences, Chengdu University of Information Technology
- 2Heavy Rainfall Research Center of China/China Meteorological Administration Basin Heavy Rainfall Key Laboratory/Hubei Key Laboratory for Heavy Rain Monitoring and Warning Research, Institute of Heavy Rain
- 3Wuhan Meteorological Bureau
Abstract
Record-breaking heatwaves arise from the interplay between long-term warming and transient atmospheric circulation anomalies, yet the mechanisms by which atmospheric circulation variability contributes to unprecedented heatwave severity remain an active area of investigation. Here, we investigate the unprecedented late-summer 2024 super heatwave with concurrent dry conditions (LS24) over the Yangtze River Basin (YRB), which produced the largest late-summer temperature anomaly during 1979–2024. We show that the record-breaking magnitude of LS24 was primarily associated with an extreme realization of a recurrent Eurasian circulation mode superimposed on a warmer background. In the full-record Empirical Orthogonal Function analysis, the event coincided with the largest positive phase of the leading mode of late-summer Eurasian circulation variability, manifested as a trans-Eurasian Rossby wave train that established persistent East Asian ridging and a heat-dome environment over the YRB through enhanced subsidence, radiation, and moisture divergence. The constructed flow analog method partitions the 4.8 °C total anomaly into a 26%–29% long-term background, a 50%–57% circulation-associated component and a 17%–21% residual; the circulation component alone accounts for 71%–77% of the detrended anomaly. Seasonal forecast ensembles further show that the ensemble-mean response produced only modest warming and failed to reproduce the observed wave-train structure, whereas similar extreme circulation states emerged within member-to-member circulation variability and were associated with stronger YRB warming. These results highlight that, under a warming climate, rare atmospheric circulation extremes can strongly modulate regional heat severity under concurrent dry conditions and represent a fundamental challenge for seasonal prediction of unprecedented climate extremes.
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BibTeX
@article{li2026unprecedented,
title = {{Unprecedented late-summer mega-heatwave over the Yangtze River Basin in 2024: dynamical fingerprint of extreme anomalous atmospheric circulation variability}},
author = {Xiao Li and Hedi Ma and Ruili Wang and Juan Zhou and Wanxin Zhang and Muyun Du and Anwei Lai and Xing Li},
journal = {Environmental Research Letters},
year = {2026},
month = oct,
doi = {10.1088/1748-9326/aeb434},
url = {https://iopscience.iop.org/article/10.1088/1748-9326/aeb434},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Unprecedented late-summer mega-heatwave over the Yangtze River Basin in 2024: dynamical fingerprint of extreme anomalous atmospheric circulation variability
AU - Xiao Li
AU - Hedi Ma
AU - Ruili Wang
AU - Juan Zhou
AU - Wanxin Zhang
AU - Muyun Du
AU - Anwei Lai
AU - Xing Li
PY - 2026
DA - 2026/10/23
JO - Environmental Research Letters
DO - 10.1088/1748-9326/aeb434
UR - https://iopscience.iop.org/article/10.1088/1748-9326/aeb434
AB - Record-breaking heatwaves arise from the interplay between long-term warming and transient atmospheric circulation anomalies, yet the mechanisms by which atmospheric circulation variability contributes to unprecedented heatwave severity remain an active area of investigation. Here, we investigate the unprecedented late-summer 2024 super heatwave with concurrent dry conditions (LS24) over the Yangtze River Basin (YRB), which produced the largest late-summer temperature anomaly during 1979–2024. We show that the record-breaking magnitude of LS24 was primarily associated with an extreme realization of a recurrent Eurasian circulation mode superimposed on a warmer background. In the full-record Empirical Orthogonal Function analysis, the event coincided with the largest positive phase of the leading mode of late-summer Eurasian circulation variability, manifested as a trans-Eurasian Rossby wave train that established persistent East Asian ridging and a heat-dome environment over the YRB through enhanced subsidence, radiation, and moisture divergence. The constructed flow analog method partitions the 4.8 °C total anomaly into a 26%–29% long-term background, a 50%–57% circulation-associated component and a 17%–21% residual; the circulation component alone accounts for 71%–77% of the detrended anomaly. Seasonal forecast ensembles further show that the ensemble-mean response produced only modest warming and failed to reproduce the observed wave-train structure, whereas similar extreme circulation states emerged within member-to-member circulation variability and were associated with stronger YRB warming. These results highlight that, under a warming climate, rare atmospheric circulation extremes can strongly modulate regional heat severity under concurrent dry conditions and represent a fundamental challenge for seasonal prediction of unprecedented climate extremes.
SN - 1748-9326
ER -