基于HYCOM数据对中尺度涡统一三维结构的研究

Study on the Universal 3D Structure of Mesoscale Eddy Based on HYCOM Data

通过分析HYCOM模式数据,利用基于物理特性的Okubo-Weiss参数化涡旋探测方法,对西北太平洋副热带逆流区中尺度涡进行探测识别,应用归一化和坐标变换方法得到了中尺度涡的统一三维结构。其中,中尺度涡的统一水平结构可以用解析函数R(r_n)=(1-r_n^2/4)·exp(-r_n^2/4)表示,与利用卫星观测资料和Argo剖面浮标得到的全球范围内统一水平结构R(r_n)=(1-r_n^2/2)·exp(-r_n^2/2)存在差异,产生这种差异的原因可能是由于模式数据分辨率高,导致在涡旋识别过程中将小尺度、次中尺度信号引进,还可能是对压强异常场进行处理时存在季节信号带来的影响。此外,2倍标准化半径范围外涡旋的压强异常分布具有明显的区域差异性,这也可能是导致统一水平结构存在差异的原因。在拉伸坐标系下中尺度涡的统一垂直结构可以表示为H_n=sin(z_n)正弦函数形式,与全球范围内观测资料得到的统一垂直结构一致。

In this paper,the Okubo-Weiss parameterized vortex detection method based on physical properties is used to identify mesoscale eddies in the subtropical countercurrent zone of the northwest Pacific Ocean.The normalization and coordinate transformation method are used to obtain the universal three-dimensional structure of mesoscale eddy.The universal horizontal structure of the mesoscale eddy can be expressed by the analytic function R(rn)=(1-rn2/4)·exp(-rn2/4),which is slightly different fro m the global horizontal structure R(rn)=(1-rn2/2)·exp(-rn2/2)obtained by using the satellite observation data and the Argo profile buoy.The reason for this difference is that the resolution of the model data is too high,which leads to the introduction of small-scale and sub-mesoscale signals in the process of vortex recognition.It may also be the effect of the seasonal signal when the pressure anomaly field is processed.In addition,the distribution of the pressure anomalyof the mesoscaleeddiesin the 2 times standard radius has obvious regional differences,which may also be the reasonfor the difference of the horizontal structure.The universal vertical structure of the mesoscale eddy can be expressed in the form of a sinusoidal function Hn=sin(zn)in the stretched coordinate,consistent with the universal vertical structure obtained from observational data on a global scale.