Anthropogenic and atmospheric circulation drivers of the record-breaking low sunshine event over Southeast China in 2024

Extreme low sunshine duration (SSD) events exert strong constraints on surface energy balance, ecosystems, and solar power generation, yet the processes governing their occurrence and evolution remain poorly understood. From April 20^th to May 4^th 2024, Southeast China (SEC) experienced a record-breaking low SSD event, marked by an anomaly of -2.53 hours. Combining ground-based observations, reanalysis, and CMIP6 simulations, we show that this extreme event resulted from the joint effects of multiple interacting anomalous circulation patterns and anthropogenic forcing. A record-breaking anticyclone anomaly over the Bay of Bengal and the westward extension of the Western Pacific subtropical high established anomalous moisture transport into SEC, where it converged with cold-air intrusions steered by a Northeast Asia blocking high, producing a persistent frontal system. A spatially-weighted constructed flow analogues analysis attributes ~70% of the event’s severity to the atmospheric circulations, with the key patterns increasing the likelihood of the extreme event by a probability ratio (PR) of 1.46. Anthropogenic aerosols further increased the event probability (PR=1.97) through thermodynamic effects, whereas greenhouse gases (GHG) dominantly amplified the key circulation anomalies. Overall, the 2024 event arose from GHG-amplified circulation anomalies acting in concert with aerosol-driven thermodynamic effects. These results highlight a synergistic role of circulation–aerosol interactions in shaping extreme sunshine variability and provide a process-based framework for anticipating similar extremes in a warming climate.