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首页> 外文期刊>Journal of the Atmospheric Sciences >Potential Vorticity of the Madden-Julian Oscillation
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Potential Vorticity of the Madden-Julian Oscillation

机译：Madden-Julian振荡的潜在涡度

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This study explores the extent to which the dynamical structure of the Madden Julian oscillation (MJO), its evolution, and its connection to diabatic heating can be described in terms of potential vorticity (PV). The signature PV structure of the MJO is an equatorial quadrupole of cyclonic and anticyclonic PV that tilts westward and poleward. This PV quadrupole is closely related to positive and negative anomalies in precipitation that are in a swallowtail pattern extending eastward along the equator and splitting into off-equatorial branches westward. Two processes dominate the generation of MJO PV. One is linear, involving MJO diabatic heating alone. The other is nonlinear, involving diabatic heating and relative vorticity of perturbations spectrally outside the MJO domain but spatially constrained to the MJO convective envelope. The MJO is thus partially a self-sustaining system and partially a consequence of scale interaction of MJO-constrained stochastic processes. Convective initiation of the MJO over the Indian Ocean features a swallowtail pattern of negative anomalous precipitation and associated anticyclonic PV anomalies at the early stage, and increasing cyclonic PV generation straddling the equator in the midtroposphere due to increasing positive anomalies in precipitation. These lead to the swallowtail pattern in positive anomalous precipitation and the associated PV quadrupole that signifies the fully developed MJO. The equatorial Kelvin and Rossby waves bear PV structures distinct from that of the MJO. They contribute insignificantly to the structure and generation of MJO PV. Solely based on the PV analysis, a hypothesis is proposed that the fundamental dynamics of the MJO depends on neither Kelvin nor Rossby waves.
机译：这项研究探索了可以用势涡（PV）来描述Madden Julian振荡（MJO）的动力学结构，其演化以及与非绝热加热的联系的程度。 MJO的标志性PV结构是赤道四极气旋和反气旋PV，其向西和向极倾斜。 PV四极与正，负降水异常密切相关，后者呈燕尾状，沿赤道向东延伸，向西分裂为赤道外分支。两个过程主导着MJO PV的产生。一种是线性的，仅涉及MJO绝热加热。另一个是非线性的，涉及非绝热加热和在MJO域之外但在空间上受MJO对流包络限制的扰动的相对涡度。因此，MJO部分是一个自我维持的系统，部分是MJO约束的随机过程的规模相互作用的结果。印度洋MJO的对流启动特征是早期出现负异常降水的燕尾模式和相关的反气旋PV异常，由于正降水异常增加，横跨对流层中赤道的气旋PV产生增加。这些导致了正异常降水中的燕尾模式以及相关的PV四极杆，这标志着MJO的充分发展。赤道开尔文波和罗斯比波具有不同于MJO的PV结构。它们对MJO PV的结构和生成贡献不大。仅基于PV分析，提出了一个假设，即MJO的基本动力学既不依赖于Kelvin波也不依赖于Rossby波。

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