The Chl a was a higher in the central than in the coastal station during April, with a large standard deviation, indicating the dynamic spring phytoplankton bloom. The climatological monthly mean SST and SSW speed showed typical features, which were related to the predictable seasonal changes of irradiance and the East Asian monsoon in the marginal seas of the northwestern Pacific Ocean. However, the SST was about 2 c higher in February and March in the central area, where the impact of the YSWC was considered to be more significant.