Understanding the characteristics of the Northeast China Cold Vortex (NCCV) during the warm season (May to September) is essential for enhancing the forecast skills in Northeast China. This study employed ERA5 reanalysis data over 2012–2022 and the optimized K-means clustering algorithm to classify NCCV tracks into five types: (A) eastward-moving dissipative, (B) eastward-moving retrogressive, (C) short-range eastward-moving offshore, (D) long-range eastward-moving offshore, and (E) long-range southeastward-moving offshore. The results demonstrated that variations in circulation configurations governed the tracks of the NCCVs, bringing about the diversity in the center intensity, lifespan, movement speed, and rainstorm probability results. Specifically, the blocking high (BH) over the Sea of Okhotsk served as the primary control system, favoring slow-moving, long-lived NCCVs (type A and type B), which were associated with a higher probability of cold vortex (CV) rainstorms. However, fast-moving, the short-lived NCCVs (type C) had a weaker impact on precipitation. A spatiotemporal analysis further revealed obvious inter-monthly variation in NCCV tracks. From May to August, under the influence of the northward-moving subtropical high and the strengthening of the BH, the occurrence of types A and B increased, while the occurrence of other types decreased. This synoptic shift promoted moisture transport into Northeast China, increasing the frequency of CV rainstorms in July and August.

GNSS radio occultation (RO) measurements are essential to global Earth observation systems. The YUNYAO constellation offers dense global coverage, high vertical resolution, and all-sky capabilities. This study proposes an improved bending-angle observation operator and presents a comprehensive evaluation of YUNYAO’s bending-angle observations against those from COSMIC-2 for December 2024. Our results indicate that YUNYAO achieves near-global coverage and provides substantially more observations than COSMIC-2. Within their region of overlap, the bending-angle quality of YUNYAO is broadly comparable to that of COSMIC-2, though YUNYAO shows a more pronounced negative relative bias above 30 km. In the vertical profile obtained by horizontally averaging the relative bias, YUNYAO exhibits a smaller bias than COSMIC-2 below 30 km. For both RO constellations, bending angles retrieved from Galileo signals exhibit a smaller relative bias than those retrieved from GLONASS in the upper atmosphere. Finally, performance differences are also evident among YUNYAO’s individual receivers.