Using Climate Forecast System Reanalysis (CFSR) data and numerical simulations, the impacts of the multi-scale sea surface temperature (SST) anomalies in the North Pacific on the boreal winter atmospheric circulations are investigated. The basin-scale SST anomaly as the Pacific Decadal Oscillation (PDO) pattern, a narrow meridional band of frontal-scale smoothed SST anomaly in the subtropical front zone (STFZ) and the spatial dispersed eddy-scale SST anomalies within the STFZ are the three types of forcings. The results of Liang-Kleeman information flow method find that all three oceanic forcings may correspond to the winter North Pacific jet changing with the similar pattern. Furthermore, several simulations are used to reveal the differences and detail processes of the three forcings. The basin-scale cold PDO-pattern SST anomaly first causes negative turbulent heat flux anomalies, atmospheric cooling, and wind deceleration in the lower atmosphere. Subsequently, the cooling temperature with an amplified southern lower temperature gradient and baroclinity brings a lagging middle warming because of the enhanced atmospheric eddy heat transport. The poleward and upward development of baroclinic fluctuations eventually causes the acceleration of the upper jet. The smoothed frontal- and eddy-scale SST anomalies in the STFZ cause comparable anomalous jet as the basin-scale by changing the upward baroclinic energy and E-P fluxes. The forcing effects of multi-scale SST anomalies coexist simultaneously in the mid-latitude North Pacific, which can cause similar anomalous upper atmospheric circulations. This is probably why it is tricky to define the certain oceanic forcing that leads to specific atmospheric circulation variation in observations

The wintertime Kuroshio sea surface temperature (SST) front have the significant climate effects on southern China. The study demonstrates a close relationship between heavy precipitation over Southern China and Kuroshio SST front in winter. More than half winter heavy rainfall events in Southern China are proved to be resulted from strong High-frequency Variability events of the sea surface Wind Coupled with Precipitation (HV-WCP) over Kuroshio SST front. One day before strong HV-WCP events, the initial precipitation appears over Middle-lower Yangtze River due to the significantly enhanced frontal intensity. Then the precipitation generates low level cyclone and southeasterly wind anomalies, after it moving into Kuroshio front area because of the winter monsoon. The significant marine atmospheric boundary layer (MABL) height gradient over Kuroshio leads to plentiful moisture transporting from MABL into free atmosphere and enhances the local precipitation again. This process further causes the large-scale stratus rainband extending to Southern China and enhancing the heavy rainfall locally. Especially in 2008 winter, several processes of a strong HV-WCP event followed by continuous weak ones are conducive to the low-temperature-precipitation disaster in Southern China

The intensity and position of the western Pacific subtropical high (WPSH) have crucial effects on climate and disaster events in East Asia during summer. The WPSH significant northward jump (SNJ) events are the main manifestation of the seasonal evolution of WPSH, which are important for the precipitation over East Asia. Using the daily reanalysis datasets from year 1979 to 2020, this study further defines the early and late SNJ events of WPSH on the interannual timescale, which are connected separately with the tropical, mid-latitude subseasonal signals and the local air-sea interaction. However, the mechanisms of the WPSH-SNJ events are different in the anomalous early and late years. In the early SNJ years, the subseasonal signals from the mid-level East Asia-Pacific teleconnection pattern or the low-level boreal summer intraseasonal oscillation cause the positive 500 hPa geopotential height anomalies, which contribute to the significant WPSH northward jump in the first pentad of July. However, the above factors are unable to cause the WPSH-SNJ in the late years. Until the second pentad of August, the collaborative effects between mid-high latitudes wave trains over high levels and cold SST anomalies in the core region lead to the barotropic geopotential height anomalies and the lagged northward jump of WPSH