This paper examines probability distributions of local wave activity (LWA), a measure of the jet stream's meander, and factors that control them. The observed column-mean LWA distributions exhibit significant seasonal, interhemispheric, and regional variations but are always positively skewed in the extratropics, and their tail often involves disruptions of the jet stream. A previously derived one-dimensional (1D) traffic flow model driven by observed spectra of transient eddy forcing qualitatively reproduces the shape of the observed LWA distribution. It is shown that the skewed distribution emerges from nonlinearity in the zonal advection of LWA even though the eddy forcing is symmetrically distributed. A slower jet and stronger transient and stationary eddy forcings, when introduced independently, all broaden the LWA distribution and increase the probability of spontaneous jet disruption. A quasigeostrophic two-layer model also simulates skewed LWA distributions in the upper layer. However, in the two-layer model both transient eddy forcing and the jet speed increase with an increasing shear (meridional temperature gradient), and their opposing influence leaves the frequency of jet disruptions insensitive to the vertical shear. When the model's nonlinearity in the zonal flux of potential vorticity is artificially suppressed, it hinders wave-flow interaction and virtually eliminates reversal of the upper-layer zonal wind. The study underscores the importance of nonlinearity in the zonal transmission of Rossby waves to the frequency of jet disruptions and associated weather anomalies.

中文翻译：

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什么控制着中纬度地区局地波活动的概率分布？

本文研究了局部波浪活动的概率分布(LWA)，射流曲流的度量，以及控制它们的因素。观察到的柱平均 LWA 分布表现出显着的季节性、半球间和区域变化，但在温带地区始终呈正偏斜，其尾部通常涉及急流的中断。由观察到的瞬态涡强迫谱驱动的先前导出的一维 (1D) 交通流模型定性地再现了观察到的 LWA 分布的形状。结果表明，即使涡流强迫是对称分布的，偏斜分布也源于 LWA 纬向平流的非线性。当独立引入时，较慢的射流和更强的瞬态和静止涡力强迫都会扩大 LWA 分布并增加自发射流中断的可能性。准地转两层模型还模拟了上层的倾斜 LWA 分布。然而，在两层模型中，瞬态涡力和射流速度都随着剪切（经向温度梯度）的增加而增加，它们的相反影响使射流中断的频率对垂直剪切不敏感。当模型在位涡纬向通量中的非线性被人为抑制时，它阻碍了波流相互作用，实际上消除了上层纬向风的逆转。该研究强调了非线性在罗斯比波的纬向传输对喷射中断和相关天气异常频率的重要性。在两层模型中，瞬态涡力和射流速度都随着剪切（经向温度梯度）的增加而增加，它们的相反影响使射流中断的频率对垂直剪切不敏感。当模型在位涡纬向通量中的非线性被人为抑制时，它阻碍了波流相互作用，实际上消除了上层纬向风的逆转。该研究强调了非线性在罗斯比波的纬向传输对喷射中断和相关天气异常频率的重要性。在两层模型中，瞬态涡力和射流速度都随着剪切（经向温度梯度）的增加而增加，它们的相反影响使射流中断的频率对垂直剪切不敏感。当模型在位涡纬向通量中的非线性被人为抑制时，它阻碍了波流相互作用，实际上消除了上层纬向风的逆转。该研究强调了非线性在罗斯比波的纬向传输对喷射中断和相关天气异常频率的重要性。位涡纬向通量的非线性被人为抑制，它阻碍了波流相互作用，实际上消除了上层纬向风的逆转。该研究强调了非线性在罗斯比波的纬向传输对喷射中断和相关天气异常频率的重要性。位涡纬向通量的非线性被人为抑制，它阻碍了波流相互作用，实际上消除了上层纬向风的逆转。该研究强调了非线性在罗斯比波的纬向传输对喷射中断和相关天气异常频率的重要性。