Climatology Characteristics of Walker Circulation in East-west Direction in the Equatorial Tropical Pacific Ocean

By using OLR monthly average data which was observed by American NOAA satellite and 500 hPa ω monthly average data of NCEP reanalysis,the indexes which represented the equatorial longitudinal circulation characteristics were defined. According to the intensity,scope and distribution characteristics of longitudinal circulation in the tropical equator area,the indexes which represented the intensity,position and scope climate characteristics of longitudinal circulation in the equatorial Pacific Ocean were diagnosed and studied. The results showed that the annual variation and interannual variation characteristics of Walker circulation in east-west direction in the equatorial Pacific Ocean were that the intensity and scope existed 5 and 15-16 years oscillatory periods,and the position had 4,12 years oscillatory periods.

Longitudinal residual circulation in the South Passage of Yangtze Estuary:Combined influences from runoff,tide and bathymetry

Classical estuary circulation theory states that in the longitudinal direction of an estuary there exists a single circulation with landward,near-bottom,and seaward,near-surface flows;however,the situation becomes complicated with the presence of a river mouth bar.Here we conducted tidal-cycle observations in the South Passage of the Yangtze Estuary during both the wet and dry seasons of 2018(July and December,respectively).The simultaneous current velocity,temperature,and salinity profile data were obtained from anchored boats and base tripods at three stations along the channel in the mouth bar area.The results reveal two distinct longitudinal residual circulation patterns:a classic circulation which is formed on the seaward slope of the mouth bar during the wet season,and a double circulation system which is composed of two circulation cells over the landward and seaward slopes of the mouth bar during the dry season.The Simpson number(Si),mixing parameter(M),and salinity data were used to quantify the mixing intensity,which shows that horizontal baroclinic pressure gradient is the dominant factor in the formation of the longitudinal residual circulation.Furthermore,the double circulation pattern during the dry season is related to the mouth bar bathymetry,which affects saltwater intrusion.The double circulations can significantly influence the spatial and temporal evolution of the stagnation point in the estuarine channel,which in turn modifies the distribution patterns of suspended sediment concentration in the maximum turbidity zone.Evidently,the changes in the mouth bar sandbar bathymetry in response to human activities and river basin hydrographic conditions indirectly affect the occurrence and scale of the double circulations.