Characteristics of the potential vorticity and its budget in the surface layer over the Tibetan plateau,International Journal of Climatology

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Characteristics of the potential vorticity and its budget in the surface layer over the Tibetan plateau
International Journal of Climatology ( IF 3.5 ) Pub Date : 2020-05-04 , DOI: 10.1002/joc.6629
Chen Sheng _{1,

2} , Guoxiong Wu _{1,

2} , Yiqiong Tang _{1,

3} , Bian He _{1,

2,

4} , Yongkun Xie ₁ , Tingting Ma ₁ , Ting Ma _{1,

3} , Jinxiao Li ₁ , Qing Bao _{1,

2} , Yimin Liu _{1,

2,

4}

Affiliation

The variability of interior atmospheric potential vorticity (PV) is linked with PV generation at the Earth's surface. The present paper reveals the features of the surface PV and provides a stepping stone to investigate the surface PV budget. In this study, the formats of the PV and PV budget adopting a generalized vertical coordinate were theoretically examined to facilitate the calculation of the surface PV and its budget. Results show that the formats of the PV and PV budget equations are independent of the vertical coordinate. While the vertical component of the surface PV dominates over the platform of the Tibetan Plateau, the horizontal component plays an important role over the slopes of the Tibetan Plateau, especially the southern slope owing to the strong in‐situ meridional gradient of the potential temperature. These results indicate that the employment of complete surface PV not only provides a finer PV structure but also more appropriately reveals its effect on atmospheric circulation. Diagnosis based on reanalysis and model output demonstrates that the surface PV budget equation is well balanced both in terms of the climate mean and synoptic process, and the surface PV budget in June has a prominent diurnal cycle. The diabatic heating with a minimum in the early morning and a maximum from evening to midnight contributes dominantly to this diurnal cycle. It is further indicated that positive PV generation due to diabatic heating is essential for the formation, development, and movement of the Tibetan Plateau vortex.

中文翻译：

青藏高原表层潜在涡度特征及其收支平衡

内部大气势涡度（PV）的可变性与地球表面的PV产生有关。本文揭示了表面PV的特征，并为研究表面PV预算提供了垫脚石。在这项研究中，理论上考察了采用广义垂直坐标的PV和PV预算的格式，以便于计算表面PV及其预算。结果表明，PV和PV预算方程的格式与垂直坐标无关。尽管表面PV的垂直分量在青藏高原的平台上占主导地位，但水平分量在青藏高原的坡度上起着重要作用，尤其是在南坡上，这是由于潜在温度的强烈子午梯度所致。这些结果表明，使用完整的表面PV不仅可以提供更精细的PV结构，还可以更适当地揭示其对大气循环的影响。基于再分析和模型输出的诊断表明，地表PV收支方程在气候均值和天气过程方面均得到了很好的平衡，并且6月的地表PV收支具有明显的昼夜周期。绝热加热在清晨最低，而从傍晚至午夜最高，是这一昼夜周期的主要因素。进一步表明，非绝热加热产生的正PV对青藏高原涡旋的形成，发展和运动至关重要。

更新日期：2020-05-04

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