由近30年的ERA5全球再分析数据采用复合方法确定了热带气旋诱发的β环流和Rossby波列。为了获取与热带气旋周围的 β 环流和罗斯比波列相关的扰动,将扰动分解为三个不同的水平尺度,包括小尺度、中尺度和行星尺度。包含中小尺度扰动的合成图显示了一个组织良好的罗斯贝波列。发现波列的方向取决于热带气旋的平移方向,除了向西-西北方向平移的方向外,还似乎分裂成两个方向。显示波列的波能沿波列轴传播,这是从波列内随时间的振幅变化推断出来的。波列呈弱向上向西倾斜,振幅随高度增加,暗示波能向上传播。从罗斯比波列中发现了一个偶极环流池,与理论和数值模型中描述的β环流非常相似。发现β环流的强度和方向随热带气旋的平移方向而变化,分别在向西和向北平移的情况下发现最弱和最强的幅度。结果表明,无论热带气旋的平移方向如何,通过滞后复合方法获得的β环流的方向都随时间顺时针旋转。波列呈弱向上向西倾斜,振幅随高度增加,暗示波能向上传播。从罗斯比波列中发现了一个偶极环流池,与理论和数值模型中描述的β环流非常相似。发现β环流的强度和方向随热带气旋的平移方向而变化,分别在向西和向北平移的情况下发现最弱和最强的幅度。结果表明,无论热带气旋的平移方向如何,通过滞后复合方法获得的β环流的方向都随时间顺时针旋转。波列呈弱向上向西倾斜,振幅随高度增加,暗示波能向上传播。从罗斯比波列中发现了一个偶极环流池,与理论和数值模型中描述的β环流非常相似。发现β环流的强度和方向随热带气旋的平移方向而变化,分别在向西和向北平移的情况下发现最弱和最强的幅度。结果表明,无论热带气旋的平移方向如何,通过滞后复合方法获得的β环流的方向都随时间顺时针旋转。与理论和数值模型中描述的β环流非常相似,是从罗斯比波列中发现的。发现β环流的强度和方向随热带气旋的平移方向而变化,分别在向西和向北平移的情况下发现最弱和最强的幅度。结果表明,无论热带气旋的平移方向如何,通过滞后复合方法获得的β环流的方向都随时间顺时针旋转。与理论和数值模型中描述的β环流非常相似,是从罗斯比波列中发现的。发现β环流的强度和方向随热带气旋的平移方向而变化,分别在向西和向北平移的情况下发现最弱和最强的幅度。结果表明,无论热带气旋的平移方向如何,通过滞后复合方法获得的β环流的方向都随时间顺时针旋转。分别在向西和向北平移的情况下发现最弱和最强的振幅。结果表明,无论热带气旋的平移方向如何,通过滞后复合方法获得的β环流的方向都随时间顺时针旋转。分别在向西和向北平移的情况下发现最弱和最强的振幅。结果表明,无论热带气旋的平移方向如何,通过滞后复合方法获得的β环流的方向都随时间顺时针旋转。
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Composite Analysis of the Beta-gyre and Rossby Wave Induced by Tropical Cyclones
Beta gyre and Rossby wave train induced by tropical cyclones were identified from the ERA5 global-reanalysis data of the recent 30 years using a composite method. To pick up the disturbances relevant to the beta gyre and Rossby wave train surrounding tropical cyclones, the disturbances were decomposed into three distinct horizontal scales including small, intermediate, and planetary-scale. Composite map of the disturbances containing small- and intermediate-scale showed a well-organized Rossby wave train. The orientation of wave train was found to depend on the translation direction of tropical cyclones, and also appeared to split into two orientations except for those translating in the west-northwestward direction. The wave energy of the wave train was shown to propagate along the wave train axis, which was inferred from the amplitude change with time within the wave train. The wave train shows a weak upward-westward tilt and increasing amplitude with height, implying the wave energy propagating upward. A dipole circulation cell, bearing a close resemblance to the beta gyre depicted in the theories and numerical models, was found from the Rossby wave train. The strength and orientation of the beta gyres were revealed to vary with the translation direction of the tropical cyclones, with the weakest and strongest amplitudes being found for the westward- and northward-translation cases, respectively. It was shown that the orientation of the beta gyre obtained by a lag-composite method rotates clockwise with time regardless of the translation direction of tropical cyclones.