The Equatorial Undercurrent（EUC） plays an important role in ocean circulation and global climate change. Near the equator, as the Coriolis parameter goes to 0, equatorial currents cannot be described by geostrophy i...The Equatorial Undercurrent（EUC） plays an important role in ocean circulation and global climate change. Near the equator, as the Coriolis parameter goes to 0, equatorial currents cannot be described by geostrophy in which the pressure gradient force term is balanced by the Coriolis force term. Many previous studies focus on the relationships between the EUC and El Ni？o-Southern Oscillation（ENSO）, the thermocline, sea surface topography, the distribution of equatorial wind stress and other atmosphere-ocean factors. However, little attention has been paid to the northward pressure gradient（NGT）, which may also be important to the EUC. The pressure can be regarded as a complex nonlinear function of terms including temperature, salinity and density.This study attempts to reveal the connection between a function of the northward pressure gradient（FNP） and the EUC. The connection is derived from primitive equations, by simplifying the equations with using scaling analysis, and shows that the beta effect may be the main reason why the FNP is important to the EUC. The vertical structure of the EUC can be partially described by the FNP. The NGT has an obvious influence on the EUC while the eastward pressure gradient has a relatively smaller effect.展开更多
基金The Open Research Fund of State Key Laboratory of Estuarine and Coastal Research of China,East China Normal University under contract No.SKLEC-KF201707the National Natural Science Foundation of China under contract No.41490642the Natural Science Foundation of Shandong Province of China under contract No.ZR2016DL09
文摘The Equatorial Undercurrent（EUC） plays an important role in ocean circulation and global climate change. Near the equator, as the Coriolis parameter goes to 0, equatorial currents cannot be described by geostrophy in which the pressure gradient force term is balanced by the Coriolis force term. Many previous studies focus on the relationships between the EUC and El Ni？o-Southern Oscillation（ENSO）, the thermocline, sea surface topography, the distribution of equatorial wind stress and other atmosphere-ocean factors. However, little attention has been paid to the northward pressure gradient（NGT）, which may also be important to the EUC. The pressure can be regarded as a complex nonlinear function of terms including temperature, salinity and density.This study attempts to reveal the connection between a function of the northward pressure gradient（FNP） and the EUC. The connection is derived from primitive equations, by simplifying the equations with using scaling analysis, and shows that the beta effect may be the main reason why the FNP is important to the EUC. The vertical structure of the EUC can be partially described by the FNP. The NGT has an obvious influence on the EUC while the eastward pressure gradient has a relatively smaller effect.
