| 青藏高原周边对流层顶的时空分布、热力成因及动力效应分析 |
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| 引用本文： | 夏昕,任荣彩,吴国雄,孙舒悦.青藏高原周边对流层顶的时空分布、热力成因及动力效应分析[J].气象学报,2016,74(4):525-541. |
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| 作者姓名： | 夏昕 任荣彩 吴国雄 孙舒悦 |
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| 作者单位： | 1.中国科学院大气物理研究所LASG, 北京, 100029 |
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| 基金项目： | 国家自然科学基金项目（91437105、41275088）、国家公益性行业（气象）专项（GYHY201406001）。 |
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| 摘 要： | 利用多套、多种再分析资料的逐日气候平均场，通过对比分析，揭示了青藏高原周边区域对流层顶分布及其季节演变的独特特征，并分析了其热力成因以及气候学效应。结果表明，与同纬度的落矶山和太平洋地区相比，青藏高原及伊朗高原区域对流层顶高度的冬夏变化幅度更大。冬季副热带对流层顶断裂带（热带对流层顶与极地对流层顶之间高度剧烈变化的过渡带）位于青藏与伊朗两个高原上空，春季开始两个高原上空对流层顶抬升迅速，夏季最高可超过热带对流层顶的高度（超过100 hPa），成为同纬度甚至全球对流层顶最高点。青藏与伊朗两个高原上空对流层顶的剧烈抬高，对应两个高原上空大气气柱比同纬度明显偏暖，同时伴随着青藏与伊朗两个高原上空位势涡度值的明显降低。因此，在青藏与伊朗两个高原区域，由春至夏等熵面强烈下凹，同时等位涡面剧烈抬升；夏季时等位涡面及对流层顶断裂带在青藏高原北部成近乎上下垂直分布，与南北倾斜分布的等位温面接近正交分布。这种特征与夏季同纬度其他地区相对平缓的对流层顶断裂带、等位涡面以及等熵面的经向分布形成强烈对比。进一步研究发现，青藏与伊朗两个高原上空由春至夏迅速发展的强大热源是引起上述对流层顶变化特征的主要原因。不同的是，青藏高原上空主要由发展强烈的对流凝结潜热所主导，而伊朗高原上空则主要由绝热下沉加热引起；此外，由春季至夏季，随着青藏高原地区对流层顶与等熵面剧烈相交分布的形成，南亚高压也逐步控制青藏高原上空，在南亚高压东缘盛行的偏北气流作用下，中高纬度平流层的高位涡空气得以在青藏高原东缘及东亚地区沿剧烈倾斜的等熵面被输送到较低纬度的对流层。与降水的季节演变对比可知，平流层高位涡输送的出现、加强和减弱与夏季降水的发展、加强与减弱成同步对应关系。从而证实了青藏高原影响夏季东亚地区形成独特气候格局的事实，说明在这种影响过程中，平流层-对流层动力相互作用过程不可忽视。
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| 关 键 词： | 对流层顶 青藏高原 平流层-对流层相互作用 经向等熵位涡输送 |
| 收稿时间： | 2015/10/27 0:00:00 |
| 修稿时间： | 4/1/2016 12:00:00 AM |
An analysis on the spatio-temporal variations and dynamic effects of the tropopause and the related stratosphere-troposphere coupling surrounding the Tibetan Plateau area |
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| XIA Xin,REN Rongcai,WU Guoxiong and SUN Shuyue.An analysis on the spatio-temporal variations and dynamic effects of the tropopause and the related stratosphere-troposphere coupling surrounding the Tibetan Plateau area[J].Acta Meteorologica Sinica,2016,74(4):525-541. |
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| Authors: | XIA Xin REN Rongcai WU Guoxiong and SUN Shuyue |
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| Institution: | 1.LASG, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China2.University of Chinese Academy of Sciences, Beijing 100049, China |
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| Abstract: | Based on multiple reanalysis datasets, this study diagnoses the spatial and temporal variations of the tropopause and the stratosphere-troposphere dynamical exchanges across the global subtropics to reveal some characteristics of the stratosphere-troposphere coupling over the Tibetan Plateau (TP) and the East Asian region. Results show that, comparing with that over the Rocky Mountains and the Pacific region in the subtropics, the tropopause over the TP and the Iranian Plateau (IP) demonstrates a much stronger seasonal variability. The steep tropopause-breaking-zone is located over the plateau in the winter, and shifts to the north of the plateau in the summer because the tropopause over the plateaus gets remarkably uplifted beyond 100 hPa and even becomes the highest ridge across the globe. The strong convective heating over the TP and the strong adiabatic heating over the IP in the summer are respectively responsible for the much warmer atmospheric columns above the plateaus. More importantly, the concave-down isentropic surfaces over the plateaus caused by the warmer temperature are accompanied with remarkable uplifting of the potential vorticity (PV) surfaces. Isentropic surfaces and PV surfaces intersect almost orthogonally over the plateaus in the summer. This characteristic distribution of isentropic surfaces and PV surfaces over the TP and IP is related to a significant PV transport from the extra-tropical stratosphere to the lower-latitude troposphere along the north-south tilted isentropic surfaces on the eastern flank of the TP. With the establishment of the South Asia High (SAH) over the TP in the summer, prevailing northerly winds over areas to the east of the SAH are favorable for the transport of PV. Moreover, the occurrence, development and disappearance of the meridional PV transport in this region are closely synchronized with that of the monsoonal precipitation. This clearly suggests that stratosphere-troposphere dynamical interactions have played an important role in the impact of the TP on the formation of the specific climate pattern and seasonal climate variation in East Asia. |
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| Keywords: | Tropopause Tibetan Plateau Stratosphere-troposphere interactions Meridional transport of isentropic potential vorticity |
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