The climate drivers of northeast cold vortex during spring sowing period in the Songnen River Basin

The Northeast Cold Vortex (NECV), a quasi-stationary cold-core cut-off low frequently occurring over Northeast Asia, plays a key role in shaping climate conditions in Northeast China. However, its basin-scale impacts, circulation controls and potential large-scale precursor signals during the spring sowing period remain insufficiently quantified. Here, using 1981-2020 reanalysis datasets and a refined objective NECV identification scheme tailored for the Songnen Plain, we show that nearly half of May precipitation occurs during NECV days, and NECV days have increased after 2010. NECVs reduce regional daily mean temperature by about 1.7 °C on average during their occurrence, underscoring their strong modulation of early-season climate. We find that blocking highs over the Okhotsk Sea are statistically associated with the steering and anchoring of cold vortices over the Songnen Plain, enhancing quasi-stationary behavior and sustaining cold and wet anomalies. Further, three large-scale impact factors show significant lead-lag relationships with May NECV activity: (1) preceding-October Niño3.4 SST anomalies, (2) preceding-January Barents Sea ice concentration, and (3) preceding-April snow depth over central West Asia. These forcing are associated with distinct Eurasian wave-train patterns that may modulate mid-tropospheric geopotential height anomalies, thus influencing NECV strength and persistence. These precursor signals provide lead times of 1-7 months and may offer useful diagnostic information for understanding NECV-related climate variability. Our findings help clarify the atmosphere-cryosphere-land surface background condition associated with NECV variability and provide insight into seasonal climate risk assessment for the Songnen Plain, a key grain-producing region of China.