Assuming homogeneity and isotropy,geostrophic turbulence theory proposes that the eddy kinetic energy follows a power law k-n with the scale distribution.However,the actual ocean is affected by various factors,such as boundaries,topography,and stratification.These elements introduce nonhomogeneous and anisotropic characteris-tics.To reconcile theory with observations,we conducted an analysis based on 30 years of altimeter data.We esti-mated the wavenumber spectrum of sea surface height anomalies(SSHAs)in different regions:tropical,subtropical,and mid-high latitudes.Following this,we evaluated the spectral slope using linear regression in the mesoscale band.The results reveal that the SSHA wavenumber spectrum steepens from the equator toward middle and high latitudes.Simultaneously,its slope decreases from-4 to-5,which agrees well with the equatorial linear wave the-ory.We found a zonal and meridional difference in the slope of the SSHA wavenumber spectrum.For instance,in the equatorial region,the zonal spectrum appears steeper than the corresponding meridional spectrum.Conversely,in the Antarctic Circumpolar Current region,the meridional spectrum slope exceeds that of the zonal spectrum.This anisotropy in the slope of the SSHA wavenumber spectrum indicates that the mesoscale motion of the ocean is af-fected by the beta effect,resulting in considerable meridional and zonal differences.In conclusion,our results demonstrate that the mesoscale motion of the ocean oscillates between quasi-two-dimensional and three-dimensional states.Therefore,it cannot be adequately described by a global turbulence theoretical model.
维普
万方数据