The China Coastal Front from Himawari-8 AHI SST Data—Part 1: East China Sea

High-resolution (2 km) high-frequency (hourly) SST data from 2015–2020 provided by the Advanced Himawari Imager (AHI) onboard Japanese Himawari-8 geostationary satellite positioned over 140.7°E were used to study spatial and temporal variability of China Coastal Front (CCF) in East Sea. This dataset was processed with Belkin O’Reilly algorithm generate long-term mean monthly maps gradient magnitude (GM) frontal frequency (FF). The horizontal structure field vicinity CCF also investigated cross-frontal distributions along eight parallels between 31°N 24°N. these 8 determine inshore offshore boundaries calculate strength defined as total step (range) dSST calculated difference SST. emerges November, fully develops December, peaks January–February. front’s fragmentation shrinking/weakening begins February March, respectively. In winter (December–February), exceeds 5 °C Zhejiang-Fujian coast could be high 7.5 when nearshore waters cool down 7 °C. winter, decreases downstream changes its physical nature seasons progress. is a water mass front cold fresh coming north warm salty south. summer, becomes coastal upwelling maintained largely southerly winds. CCF’s ramp-shaped, increasing monotonously direction. V-shaped or U-shaped, featuring minimum formed upwelled at some distance shore. Thus, summer effectively consists two parallel fronts, an one one, between. Across inshore/offshore front, decreases/increases