A Systematic Comparison of Tropical Waves over Northern Africa. Part II: Dynamics and Thermodynamics
A Systematic Comparison of Tropical Waves over Northern Africa. Part II: Dynamics and Thermodynamics
复制标题
北非热带波的系统比较。
作者：
A. Schlueter;A. Fink;P. Knippertz
这项研究首次系统地比较了引起热带非洲北部降水调制的所有主要热带波动类型的动力学和热力学：Madden-Julian振荡(MJO)、赤道Rossby波(ERs)、热带扰动(TDS，包括非洲东风波)、Kelvin波、混合Rossby重力波(MRGs)和向东的惯性重力波(EIGs)。根据传出长波辐射的时空滤波，分析了1981-2013年期间的再分析和无线电探空仪数据。识别出的环流模式与理论基本一致。慢模式MJO和ER主要影响可降水量，而较快的TDS、Kelvin波和MRGs主要调制水汽辐合。季风流入在MJO、ERS和MRG的湿位相期间增强，与MJO和ERS的热带不连续向北移动有关。这项研究表明，非洲上空的MRG具有明显不同于AEW的明显动力结构。在垂直倾斜的不平衡波(如MJO、TDS、Kelvin波和部分MRG波)的传播过程中，垂直风切变的增加和上下气流条件的改善有利于中尺度对流系统的组织。平衡的ERS没有倾斜，降雨是由大范围增湿和层状抬升引发的。MJO和ERS与印度季风和温带Rossby波列的季节内变化相互作用。后者在阿特拉斯山脉上造成了一个低谷，与热带羽流和撒哈拉沙漠上的降雨有关。提出的结果揭示了需要对哪些动力过程进行现实建模，以反映热带非洲北部热带波和降雨之间的耦合。
This study presents the first systematic comparison of the dynamics and thermodynamics associated with all major tropical wave types causing rainfall modulation over northern tropical Africa: the Madden–Julian oscillation (MJO), equatorial Rossby waves (ERs), tropical disturbances (TDs, including African easterly waves), Kelvin waves, mixed Rossby–gravity waves (MRGs), and eastward inertio-gravity waves (EIGs). Reanalysis and radiosonde data were analyzed for the period 1981–2013 based on space–time filtering of outgoing longwave radiation. The identified circulation patterns are largely consistent with theory. The slow modes, MJO and ER, mainly impact precipitable water, whereas the faster TDs, Kelvin waves, and MRGs primarily modulate moisture convergence. Monsoonal inflow intensifies during wet phases of the MJO, ERs, and MRGs, associated with a northward shift of the intertropical discontinuity for MJO and ERs. This study reveals that MRGs over Africa have a distinct dynamical structure that differs significantly from AEWs. During passages of vertically tilted imbalanced wave modes, such as the MJO, TDs, Kelvin waves, and partly MRG waves, increased vertical wind shear and improved conditions for up- and downdrafts facilitate the organization of mesoscale convective systems. The balanced ERs are not tilted, and rainfall is triggered by large-scale moistening and stratiform lifting. The MJO and ERs interact with intraseasonal variations of the Indian monsoon and extratropical Rossby wave trains. The latter causes a trough over the Atlas Mountains associated with a tropical plume and rainfall over the Sahara. The presented results unveil which dynamical processes need to be modeled realistically to represent the coupling between tropical waves and rainfall in northern tropical Africa.
影响因子：
3.1
作者：
Yang, Gui-Ying;Methven, John;Hoskins, Brian
通讯作者：
Hoskins, Brian
西半球热带大气波的等效正压结构
影响因子：
3.1
作者：
Yang G
通讯作者：
Yang G