ABSTRACT Using the National Centers for Environmental Prediction–Department of Energy Atmospheric Model Intercomparison Project 2 daily reanalysis datasets, the present study reveals that an upper tropospheric vertical thermal contrast (VTC) exists between pressure levels at 100 and 250 hPa over the Mediterranean region (MR) during the midsummer monsoon. An increase and decrease in the tropospheric temperature (TT) at the 100 and 250 hPa levels respectively, are found to be centred over the MR during El Niño years. The former is characterized by an anticyclonic circulation in the wind shear and the latter by a cyclonic circulation. The opposite pattern is exhibited during La Niña years. It is shown that the MR VTC remotely affects convection over the western Tibetan Plateau (WTP) by inducing favourable temperature, circulation patterns, and ascending (descending) winds on the upper vertical levels of the WTP during El Niño (La Niña) years. This effect has been further substantiated by a careful causality analysis with a new causal inference technique, which identifies a dominant causality from the MR VTC to the WTP longwave fluxes through the top of the atmosphere.

中文翻译：

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ENSO年间地中海地区对流层上层垂直热对比对青藏高原西部对流的影响

摘要 本研究使用国家环境预测中心 - 能源部大气模型比对项目 2 每日再分析数据集，表明地中海地区 (MR) 上空 100 至 250 hPa 的压力水平之间存在对流层上层垂直热对比 (VTC) ) 在仲夏季风期间。发现在厄尔尼诺年期间，分别在 100 和 250 hPa 水平的对流层温度 (TT) 的升高和降低以 MR 为中心。前者以风切变中的反气旋环流为特征，后者以气旋环流为特征。拉尼娜年则表现出相反的模式。结果表明，MR VTC 通过诱导有利的温度、环流模式、和在厄尔尼诺（拉尼娜）年期间 WTP 上垂直水平面上的上升（下降）风。使用新的因果推断技术进行仔细的因果分析进一步证实了这种影响，该技术确定了从 MR VTC 到穿过大气顶部的 WTP 长波通量的主要因果关系。