Mesoscale eddies are omnipresent and play an important role in regulating Earth’s climate and ocean circulation in the global ocean. Here using the combination of satellite altimetry products and Argo float profile data, two types of abnormal eddies are investigated: WCEs(warm cyclonic eddies) and CAEs(cold anticyclonic eddies) with different cores than conventional eddies in the Japan/East Sea. By applying a classification method based on the calculation of the heat content anomalies in the upper ocean, it was found that 10% of the eddies that captured the Argo float profiles exhibited obvious abnormal features. Subsequently, their spatiotemporal distributions and characteristics were analyzed statistically. Three-dimensional structures of abnormal eddies were obtained via the composite analysis method, showing that the warm/cold and light/dense core of the composite WCE/CAE is confined to the upper 100 m of the ocean with a maximum temperature anomaly of approximately +1.0(-1.1)°C. The composite WCE had a double-core salinity structure with a salty core above 50 m and an inferior fresh core. Meanwhile composite CAE had a fresh single-core with a maximum magnitude of -0.05 psu. Abnormal eddies are pervasive in the Japan/East sea, a revaluation of the role of these eddies in ocean circulation and climate systems, such as heat and salt transport, air and sea interaction, and variability in mixed layer depth, is of great importance.

Traditional composite methods for mesoscale eddies predominantly employ simplistic geographical partitioning, seldom taking into account the variations in mesoscale eddy structures that are jointly influenced by seasonal and regional factors within the area., nor does it consider the issue of approximating mesoscale eddies as elliptical structures. This study combines mesoscale eddy data from satellite altimetry (2007-2022) with Argo profile data captured by eddies to propose a mesoscale eddy composite analysis method based on profile clustering and an elliptical model. This method provides the three-dimensional structures of various types of mesoscale eddies in the Philippine Sea. The results show that the eccentricity of the best-fitting ellipses for mesoscale eddies in the Philippine Sea is predominantly between 0.7 and 0.9, with the orientation of the major axis mostly directed at 80° northeast. Based on sound speed profile clustering, mesoscale eddies are classified into five categories. The composite eddy anomaly structures exhibit a clear correlation with the profile types. Compared to the single mesoscale eddy structure obtained by the traditional mesoscale eddy composite method, this approach accurately composites five typical mesoscale eddy structures in the Philippine Sea, and its elliptical shape is more consistent with actual observational results.

Current wind energy planning in the China Seas and adjacent waters generally focuses on wind speed or wind power density (WPD), yet lacks sufficient understanding of the long-term climatic evolution patterns and climatic driving mechanisms of effective wind speed occurrence (EWSO) and its correlation with climate oscillations. Based on the ERA5 10 m sea surface wind reanalysis data from the European Centre for Medium-Range Weather Forecasts (ECMWF) and multiple key climate index datasets from 1941 to 2020, this study systematically analyzed spatiotemporal distribution characteristics, long-term variation trends, and correlations with climate oscillations of EWSO in the China Seas and adjacent waters. The results indicated the following: (1) There are discrepancies between the distribution of EWSO and mean wind speed. (2) Over the past 80 years, EWSO across the study area has shown an overall significant increasing trend with pronounced regional disparities, among which the Yellow–Bohai Sea area has exhibited a significant decreasing trend. (3) The interannual variability of EWSO is regulated by climate oscillations such as ENSO. This study demonstrates that incorporating EWSO as an independent indicator separate from wind speed into the wind energy resource assessment system is crucial for identifying offshore wind power generation risks and more accurately evaluating the actual operational duration of wind farms in China’s offshore waters and adjacent sea areas. The correlation between EWSO and climate oscillations such as ENSO provides an important scientific basis for improving seasonal prediction models of wind energy resources.

Conventional wisdom about mesoscale eddies is that cyclonic (anticyclonic) eddies are commonly associated with cold(warm) surface cores. Nevertheless, plenties of surface warm cyclonic eddies (WCEs) and cold anticyclonic eddies (CAEs) in the North Pacific Subtropical Countercurrent (STCC) region are observed by a synergistic investigation based on data from satellite altimetry, microwave radiometer, and Argo float profiles in this study. The results indicate that these two types of abnormal eddies (WCEs and CAEs) are prevalent in the STCC region, comprising approximately 30% of all eddies detected via satellite observations. We then analyze their spatial-temporal distribution characteristics and composite vertical structures. A statistical comparison with surface cold cyclonic eddies (CCEs) and warm anticyclonic eddies (WAEs) reveals notable differences between the anomalous and typical eddies. Additionally, we present the composite vertical structures of temperature and salinity anomalies for the anomalous eddies across five delineated subregions within an eddy-coordinate system. Furthermore, the close relationship between these abnormal eddies and subsurface-intensified mesoscale eddies are discussed.