Changes in climatic features of Northeast China Cold Vortex as reflected by ERA5 and CRA-40

The Northeast China Cold Vortex (NEC-CV) is an important part of the mid-latitude circulation system, which usually leads to high-impact weather over central China. As essential tools, global reanalysis products are widely used to understand the characteristics and mechanisms of NEC-CVs. In this study, changes in climatic features of NEC-CVs are comprehensively investigated based on the two latest reanalysis datasets (ERA5 and CRA-40). The results show that changes in climatic characteristics derived from CRA-40 are spatially and temporally consistent with that from ERA5. Climatologically, most NEC-CVs last for 3-4 days and have radii ranging from 250 to 750 km. For both datasets, there are strong decadal variabilities in the frequency and duration of NEC-CV in all seasons. In addition, obvious changes are also found in different metrics of NEC-CVs, with both datasets displaying significant increasing trends in depth and radius in February and November, respectively. Along with the northward movement of the jet stream, poleward migration of NEC-CVs is found statistically significant in May by both ERA5 and CRA-40 datasets.