Xuejie Zhao

The Meiyu season over the Yangtze–Huaihe River Basin exhibits pronounced interannual variability and directly reflects the persistence of the East Asian summer rainband. This study examined the relationship between the preceding April sea ice anomaly of the Barents–Kara seas and Meiyu length during 1979–2023 based on CN05.1 precipitation, ERA5, HadISST sea ice concentration datasets, and Indo-Pacific SST index. A statistically significant inverse relationship was identified between the interannual Meiyu Length and the preceding April Barents–Kara seas sea ice anomaly, with the strongest signal located over the core Barents–Kara seas sector and a filtered Barents–Kara seas sea ice index–Meiyu length index correlation coefficient of −0.662. Composite and regression analyses demonstrated that reduced interannual April Barents–Kara seas sea ice concentration is associated with a downstream Rossby-wave-like upper-tropospheric circulation pattern, leading to a clearer upper-level potential vorticity band and an intensified westerly jet that generates increased convergence over the Yangtze–Huaihe River Basin. Additionally, the north-low–south-high circulation contrast over the East Asian–western North Pacific sector during years with a longer Meiyu period, associated with an interannual reduction in the Barents–Kara seas sea ice index, contributes to enhanced moisture convergence and convection that drive stronger ascent over the Yangtze–Huaihe River Basin, favoring a more persistent Meiyu rainband and a longer Meiyu period.

Meiyu is a critical component of the summer rainy season over the Yangtze–Huaihe River Basin (YHRB) in China, and the Meiyu onset date (MOD), serving as a key indicator of Meiyu, has garnered substantial attention. This article demonstrates an in-phase relationship between MOD and the preceding spring Barents–Kara Seas ice concentration (BKSIC) during 1979–2023. Specifically, the loss of spring BKSIC promotes an earlier MOD. Further analysis indicates that decreased spring BKSIC reduces the reflection of shortwave radiation, thereby enhancing oceanic solar radiation absorption and warming sea surface temperature (SST) in spring. The warming SST persists into summer and induces significant deep warming in the BKS through enhanced upward longwave radiation. The BKS deep warming triggers a wave train propagating southeastward to the East Asia–Northwest Pacific region, leading to a strengthened East Asian Subtropical Jet and an intensified Western North Pacific Subtropical High in summer. Under these conditions, the transport of warm and humid airflows into the YHRB is enhanced, promoting convective instability through increased low-level warming and humidity, combined with enhanced wind shear, which jointly contribute to an earlier MOD. These results may advance the understanding of MOD variability and provide valuable information for disaster prevention and mitigation.