Subjects: Other Disciplines >> Synthetic discipline submitted time 2023-03-28 Cooperative journals: 《中国科学院院刊》
Abstract： The total amount of radiation over the Tibetan Plateau (TP) is the largest in the world with an extreme area of super solar constant, where a huge heat source “embedded” in the middle troposphere forms a hollow heat island with the effect exceeding any urban agglomerations in the world and an inestimable driving impact on global and regional changes in atmospheric circulation system. In closely association with the seasonal variations of TP’s thermal forcing, the Asian summer monsoon is the most widely in the world with the strongest monsoon intensity. The seasonal changes of solar radiation results in a “rapid response” of sensible heat and its dynamic movement over the TP’s large terrain. The advancing cold-rainfall belts of East Asian summer monsoon stop just along the mountain-plain boundary area in China’s three ladder terrain distribution, indicating that the TP may play key role in summer monsoon process of air-sea-land interactions. The extreme regions of low cloud cover and total cloud cover over China, the sources of large rivers (Yangtze River, Lancang River, Yarlung Zangbo River, etc.) in the TP and the group of lakes and rivers in central-eastern China are spatially almost consistent, reflecting that an inseparable connection of the formation of “Asian Water Tower” and the unique cloud precipitation structure in the TP. The studies revealed that a significant influence of the TP’s atmospheric heat source on the cloudprecipitation and water vapor transport pattern in local and downstream areas. The precipitation in the Yangtze River Reaches has an obvious zonal high correlation structure with the low cloud cover over China, the precipitation in the Yangtze River Reaches has an important relation with the thermal divers of upper TP’s Asian Water Tower, and convection system. From the perspective of acrossequatorial circulations, it is found that the summertime cross-equatorial lower south and upper-north flows between the northern to southern hemispheric atmosphere appears just in the Asian and the North American regions with the TP and the Rocky Mountains. The TP’s zonal and meridional circulation structure and the relevant mechanism of regional and global atmospheric circulation confirm the thermal role of the TP’s “roof of the world” and the convection activities in global energy and water circles. The three-dimensional distribution of special water vapor on the TP and the vertical circulation of atmosphere across the hemispheres show that the TP contributes significantly to the change of global atmospheric circulation. A global Water Tower concept in the TP’s atmosphere was put forward, and it is believed that the “water supply” and “water storage” system of TP’s water tower is built with the “water storage tank” system of the plateau surface glaciers, snow cover and lakes, as well as “water supply pipelines” of rivers transporting water from the water tower to the downstream areas, and the upper atmosphere also provides the channels for outward transport of water vapor from the TP. The TP’s special atmospheric water circulation across the hemisphere can establish “water tower of the world” and its surrounding areas the unique hydrological function, which could provide a comprehensive description of physical picture about the TP’s “water tower of the world” and the land-sea-air water vapor circulation in global scale.
Subjects: Geosciences >> Other Disciplines of Geosciences submitted time 2019-09-10 Cooperative journals: 《干旱区研究》
Abstract：借助观测资料与FNL全球分析资料，对比研究2017年与2014年西安高温天气基本特征与有利环流形势，结果表明：① 2 a西安均发生了40 ℃以上的长时间持续高温天气，其中2014年属于常规高温年份，而2017年西安高温则提前1个月发生，高温的提前发生主要是因为南亚高压强于正常年份同期强度；② 不同于我国南方地区的闷湿高温，西安高温属于干性高温，且昼夜温差较小，由此造成24 h对人体的不适；③ 详细描述了西安高温发生的典型环流特征，即南亚高压与西太平洋副热带高压（简称副高）同时增强，并在对流层中高层相互贯通；④ 南亚高压是影响我国西北地区的主要热源基地，在较大经向度的有利环流背景下，强风速可将热气团向南向东深度输送至下游地区（即西安）；⑤ 在“上辐合、下辐散”的散度场配置下，西安500 hPa以下高空维持明显的下沉气流，加之有利的局部要素相配合，最终造成该地区高温天气的发生。
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