30—50 天振荡动能特性及其与平均气流正压不稳定能的转换

该文利用冬季500 hPa的欧洲中心（ECMWF）网格点逐日资料，分析了30—50天振荡的E矢量分布、动能特性及平均气流的正压不稳定能转换特征，从而得到:30—50天振荡的能量传播与西风急流的位置有密切的关系，在西风大风速区作纬向能量传播，在小风速区作指向赤道的经向传播；在急流的出口区有较强的正压能转换，低频振荡从基本流中获得能量，使这里的低频动能最大，并表现出较强的正压特性，与低纬度的斜压特性形成鲜明对照。

The Special Property of Kinetic Energy of 30—50 Day Oscillation and Its Relationship to the Barotropic Instability of Basic Flow

By using ECMWF day–to–day grid data, the distribution of vector E, the special property of kinetic energy and the features of the barotropic instability for 30–50 day oscillation are analyzed. It is found that the energy propagation of 30–50 day disturbance is closely related to the location of the west wind jet. The wave energy propagates zonally at the place where the west wind is stronger but meridionally at the place where that is weaker. Due to the stronger conversion of barotropic energy, the disturbance with low—frequency can get energy from basic flow, which causes the greatest kinetic energy of these disturbances in the jet exit region. The vertical distributions of kinetic energy here show us the fairly barotropic characteristics which strongly contrasted to the baroclinic over area of low latitudes