Synthesis of Vortex Rossby Waves. Part III: Rossby Waveguides, Vortex Motion, and the Analogy with Midlatitude Cyclones
Synthesis of Vortex Rossby Waves. Part III: Rossby Waveguides, Vortex Motion, and the Analogy with Midlatitude Cyclones
复制标题
涡罗斯贝波的合成。
DOI：
10.1175/jas-d-20-0197.1
复制
发表时间：
2021
影响因子：
3.1
通讯作者：
Willoughby, H. E.
中科院分区：
文献类型：
--
作者：
Gonzalez III, Israel;Willoughby, H. E.
涡旋Rossby波（VRW）影响热带气旋（TC）的运动、结构和强度。它们在环形波导内传播，该环形波导由Ω1D（一维VRW的多普勒频移频率）和零之间的通带限定。波数为1的VRW直接引起TC运动，并且具有比波数≥ 2的波导更宽的波导。以固定旋转频率强迫的VRW远离强迫传播。最初向外传播的波在临界半径处多普勒频移为零，在那里它们被吸收。最初向内传播的波多普勒频移到Ω1D，从转折点反射，向外传播，并最终在临界半径处被吸收。在强迫和转弯半径之间，VRW具有驻波结构;从强迫向外，它们是拖尾螺旋。它们携带角动量通量，在强迫半径处加速平均流，在临界半径处减速。平均流涡度单极子与球形地球上的斯托克斯定理不一致，因为包围地球对极的等高线将具有非零环流，但将包围零涡度。Rossby波导范例也适合天气尺度Rossby波在纬向剪切流。这些波在一个限制在向极转向纬度和向赤道临界纬度之间的波导中传播。强迫波是类似于观测到的锋面气旋的逗号形涡旋，其尾丝朝向强迫纬度的赤道方向，驻波朝向极地方向。即使是中性的强迫Rossby波也会在强迫纬度处汇聚西风动量。
Vortex Rossby waves (VRWs) affect tropical cyclones’ (TCs’) motion, structure, and intensity. They propagate within annular waveguides defined by a passband between Ω1D, the Doppler-shifted frequency of a one-dimensional VRW, and zero. Wavenumber-1 VRWs cause TC motion directly and have wider waveguides than wavenumbers ≥ 2. VRWs forced with fixed rotation frequency propagate away from the forcing. Initially outward-propagating waves are Doppler shifted to zero at a critical radius, where they are absorbed. Initially inward-propagating waves are Doppler shifted to Ω1D, reflect from a turning point, propagate outward, and are ultimately absorbed at the critical radius. Between the forcing and the turning radii, the VRWs have standing-wave structure; outward from the forcing they are trailing spirals. They carry angular momentum fluxes that act to accelerate the mean flow at the forcing radius and decelerate it at the critical radius. Mean-flow vorticity monopoles are inconsistent with Stokes’s theorem on a spherical Earth, because a contour enclosing the monopole’s antipode would have nonzero circulation but would enclose zero vorticity. The Rossby waveguide paradigm also fits synoptic-scale Rossby waves in a meridionally sheared zonal flow. These waves propagate within a waveguide confined between a poleward turning latitude and an equatorward critical latitude. Forced waves are comma-shaped gyres that resemble observed frontal cyclones, with trailing filaments equatorward of the forcing latitude and standing waves poleward. Even neutral forced Rossby waves converge westerly momentum at the latitude of forcing.