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首页> 外文期刊>Journal of the Atmospheric Sciences >The Tropospheric Response to Tropical and Subtropical Zonally Asymmetric Torques: Analytical and Idealized Numerical Model Results
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The Tropospheric Response to Tropical and Subtropical Zonally Asymmetric Torques: Analytical and Idealized Numerical Model Results

机译：对流层对热带和亚热带区域非对称扭矩的响应：解析和理想数值模型结果

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摘要

The tropospheric response to prescribed tropical and subtropical zonally asymmetric torques, which can be considered as idealizations of vertical momentum transfers by orographic gravity waves or convection, is investigated. The linear analytical Gill model response to westward upper-tropospheric torques is compared to the response to a midtropospheric heating, which is a familiar point of reference. The response to an equatorial torque projects onto a Kelvin wave response to the east that is of opposite sign to the response to the east of the heating at upper levels. In contrast, the torque and heating both produce Rossby gyres of the same sign to the west of the forcing and the zonal-mean streamfunction responses are identical. When the forcings are shifted into the Northern Hemisphere, the streamfunction responses have opposite signs: there is upwelling in the Southern (Northern) Hemisphere in response to the torque (heating). The nonlinear response to westward torques was explored in idealized general circulation model experiments. In the absence of a large-scale meridional temperature gradient, the response to an equatorial torque was confined to the tropics and was qualitatively similar to the linear solutions. When the torque was moved into the subtropics, the vorticity budget response was similar to a downward control type balance in the zonal mean. In the presence of a meridional temperature gradient, the response to an equatorial torque involved a poleward shift of the midlatitude tropospheric jet and Ferrel cell. The response in midlatitudes was associated with a poleward shift of the regions of horizontal eddy momentum flux convergence, which coincided with a shift in the upper-tropospheric critical line for baroclinic waves. The shift in the critical line was caused (in part) by the zonal wind response to the prescribed torque, suggesting a possible cause of the response in midlatitudes. Overall, this hierarchy of analytical and numerical results highlights robust aspects of the response to tropical and subtropical zonally asymmetric torques and represents the first step toward understanding the response in fully comprehensive general circulation models.
机译：研究了对流层对规定的热带和亚热带纬向不对称扭矩的响应，可以将其视为通过地形重力波或对流进行的垂直动量传递的理想化。将线性分析吉尔模型对西对流层上层扭矩的响应与对中对流层加热的响应进行比较，这是一个常见的参考点。对赤道转矩的响应投射到对东方的开尔文波响应上，这与高层加热对东方的响应相反。相比之下，扭矩和加热都在强迫力的西边产生具有相同符号的Rossby回转，并且区域平均流函数响应相同。当强迫转移到北半球时，流函数响应具有相反的迹象：响应扭矩（加热），南（北）半球出现上升流。在理想化的一般循环模型实验中探索了对向西扭矩的非线性响应。在没有大尺度子午温度梯度的情况下，对赤道转矩的响应仅限于热带，并且在质量上与线性解相似。当扭矩移入亚热带时，涡度预算响应类似于纬向均值中的向下控制类型平衡。在存在子午温度梯度的情况下，对赤道扭矩的响应涉及中纬对流层射流和Ferrel单元的极移。中纬度地区的响应与水平涡动量通量收敛区域的极移有关，这与斜压波的对流层上临界线发生了偏移。临界线的偏移（部分）是由纬向风对规定扭矩的响应引起的，表明中纬度地区响应的可能原因。总的来说，这种分析和数值结果的层次结构突出了对热带和亚热带区域性非对称扭矩响应的稳健方面，并代表了在全面全面的一般环流模型中理解响应的第一步。

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