Behaviours of Extreme Sunshine Duration Events in Eastern China

ABSTRACT Extreme sunshine duration events (ESDEs) are characterized by anomalously long sunshine and intense solar radiation. ESDEs severely threaten ecosystem functions and human health by disrupting photosynthesis and elevating skin cancer risks, but how these events occur and evolve remains largely unclear. Here, we present an investigation of the synoptic behaviours and driving mechanisms of ESDEs by taking eastern China as an example, using a homogenized daily dataset. We identify four ESDE hotspots featured by persistent anticyclonic and high‐pressure anomalies, which promote clear, dry, and stable atmospheric conditions. In the Middle Yangtze River valley, ESDEs are associated with a northward extension of the high‐pressure system, which strengthens subsidence and suppresses moisture. In the hotspots of Central and North China, a midlatitude wave train linked to a blocking extension of high‐pressure ridge from the northwest parts and a high‐pressure centre over the Sea of Japan is identified. Meanwhile, Central China is also modulated by persistent near‐surface anticyclonic conditions before and during the ESDEs, creating hotter and drier atmospheric columns. In comparison, ESDEs in Northeast China are mainly controlled by the joint influence of the Northeast Asian thermal high and the high‐pressure system over Mongolia. Understanding the synoptic behaviours and mechanisms of ESDEs advances our knowledge of such weather hazards to better mitigate their detrimental effects.