A China-Japan Cooperative JICA Atmospheric Observing Network over the Tibetan Plateau (JICA/Tibet Project) : An Overviews (Special Issue on Japan-China Meteorological Disaster Reduction Corporation Research Center Project (JICA/Tibet Project))
A China-Japan Cooperative JICA Atmospheric Observing Network over the Tibetan Plateau (JICA/Tibet Project) : An Overviews (Special Issue on Japan-China Meteorological Disaster Reduction Corporation Research Center Project (JICA/Tibet Project))
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DOI：
10.2151/jmsj.2012-c01
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发表时间：
2012-07
影响因子：
3.1
通讯作者：
Renhe Zhang;T. Koike;Xiangde Xu
中科院分区：
文献类型：
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作者：
Renhe Zhang;T. Koike;Xiangde Xu
鉴于青藏高原对中国、亚洲乃至世界大气环流和气候的重要影响，中日两国科学家于2005—2009年在日本国际协力机构（JICA）项目（JICA/西藏项目）下共同建设了青藏高原及其邻近地区综合大气观测系统，特别是水汽观测。 JICA/西藏项目旨在了解青藏高原的陆地-大气相互作用过程及其对青藏高原及其东部东亚地区恶劣天气和气候的影响。该项目旨在通过提高预报能力来减轻这些地区气象灾害的影响。项目的实施增强了高原大气监测能力。数值预报技术是通过将观测数据同化到数值模型中而发展起来的。在观测地表能量平衡研究的基础上，改进了地表模型。研究发现，高原降水日变化与水汽密切相关，潜热释放是影响高原低涡的主要因素。通过分析观测到的对流层顶季节特征，为青藏高原上空存在强烈的平流层和对流层交换提供了证据。揭示了华东地区夏季降水的年际变化与高原植被指数的年际变化相对应。高原热力和机械力驱动的跨半球环流不仅在东亚乃至全球范围内的水汽输送中发挥着重要作用。 1. 背景和动机青藏高原位于亚洲中部的北纬25-40度、东经74-104度的亚热带地区。它是世界上海拔最高的高原，地形极为复杂。高原平均海拔在4000米至5000米之间 通讯作者：张仁和：中国气象科学研究院，北京市海淀区中关村南大街46号 100081。 E-mail: renhe@cams.cma.gov.cn 2012年6月，日本气象学会海拔高度，因此也被称为“世界屋脊”、“第三极”。高原东以横断山脉为界，南、西与喜马拉雅山脉接壤，北依昆仑山。高原大部分地区位于中国西南部，包括西藏自治区、青海省、四川省西部、新疆维吾尔自治区南部以及甘肃省和云南省的部分地区。从地理上看，还包括不丹、尼泊尔、印度、巴基斯坦、阿富汗、塔吉克斯坦、吉尔吉斯斯坦的部分地区。高原面积250万平方公里，其中240万平方公里位于中华人民共和国境内。青藏高原是一块突出于地球表面的巨大陆地，一直延伸到对流层中部。因此，高原上空的温度、湿度、气压等气象要素与周围自由大气有明显不同。在北半球夏季，高原是对流层中层的巨大热源，在北半球冬季是冷源（Ye和Gao，1979）。其热力和动力效应对中国、亚洲乃至全世界大气环流和气候的形成和演变产生重大影响(Ye等，1957，1998；Huang，1985；Yanai等，1992)。高原上空形成的涡旋及其东移对我国东部地区的暴雨产生了至关重要的影响。例如，1963年袭击华北的特大暴雨和1954年席卷长江流域的特大洪水都与高原涡旋东移有关（陶和丁，1981）。高原的动力和热力作用对于中国梅雨期水汽向长江流域的输送起着关键作用(Xu et al., 2002)。高原的显热驱动气泵（SHAP）效应不仅维持了亚洲的夏季风，而且还通过诱发罗斯贝波列影响全球气候（Wu et al. 1997）。最近还确定了潜热和显热的影响。 Fujinami 和 Yasunari (2001) 研究了高原云活动的季节性变化，报告了春季（3 月至 4 月）云活动显着。上田等人。 (2003)还证明了西部高原夏季风爆发前阶段凝结加热在热平衡中的重要性。 2004 年 4 月，在协调增强观测期（CEOP）的框架下，对青藏高原进行了第一次早春密集实地观测（Koike 2004）。基于现场和卫星观测以及数值模拟，Taniguchi 和 Koike (2007) 报告了积云活动对于对流层上层大气温度升高的重要性，即使在四月份也是如此。北半球冬季，青藏高原热源的变化可能会在赤道太平洋孕育出异常的纬向风，进而导致海面温度异常，最终影响ENSO事件（Chen等，2001）。近年来，中国气象灾害发生频率有所增加（中国气象局，2007）。中国一直致力于建立功能完善的气象观测网络，以满足防灾减灾的需要。然而，与东部地区相比，西部地区运行的气象站数量明显较少（Zhang，2006）。青藏高原约占国土面积的四分之一，由于海拔高、自然环境恶劣、观测难度大，气象站数量与其幅员面积极不成比例。如此广阔的区域观测数据的匮乏，不仅影响了科学研究，而且对青藏高原及其东部地区，特别是长江、黄河流域以及其他东亚国家的高影响天气事件预测的可靠性和准确性提出了质疑。考虑到青藏高原对研究和预测中国乃至东亚天气气候演变的重要性，有必要提高“世界屋脊”及其邻近地区的大气监测能力和实用性，增强我国灾害性天气预报和防灾减灾能力。考虑到建立青藏高原综合大气观测系统的重要性，1999年12月中日两国政府将青藏高原大气联合观测与研究确定为重点合作课题之一。2002年7月，中国气象科学研究院第2期日本气象学会学报第2期，第1期。 90℃
Because of the importance of the impact of the Tibetan Plateau on atmospheric general circulations and climate across China, Asia, and even the world, Chinese and Japanese scientists jointly constructed an integrated atmospheric observing system, especially for the water vapor observation, across the Tibetan Plateau and its adjacent areas during the period of 2005–2009 under the JICA (Japan International Co-operation Agency) project (JICA/Tibet Project). The JICA/Tibet Project aims at understanding processes of the land-atmosphere interaction over the Tibetan Plateau and their impacts on the severe weather and climate over the Tibetan Plateau and the area to its east in the East Asian region. The project is designed in an attempt to alleviate impacts of meteorological disasters in these areas through improving the prediction skill. The implementation of the project has enhanced the capability of monitoring the Plateau atmosphere. The numerical forecast techniques are developed through assimilating observed data into the numerical model. Based on the investigation of observed surface energy balance, the land surface model is improved. It is found that the diurnal variation of precipitation over the Plateau is closely related with water vapor, and the latent heat release is a main factor a¤ecting the Plateau vortex. By analyzing observed seasonal features of the tropopause, the evidence of strong stratosphere and troposphere exchange over the Tibetan Plateau is provided. It reveals that the interannual variability of summer rainfall in East China corresponds to that of vegetation index over the Plateau. The crossing hemispheric circulations driven by the thermal and mechanical forcings of the Plateau play an important role in water vapor transports not only over East Asia, but also in the global scale. 1. Background and motivation The Tibetan Plateau sits in the subtropical area within 25 N–40 N, 74 E–104 E in the middle of Asia. It is the highest plateau in the world, with extremely complex terrains. The Plateau’s averaged elevation ranges between 4,000 m and 5,000 m Corresponding author: Renhe Zhang: Chinese Academy of Meteorological Sciences, No. 46 Zhong-GuanCun South Ave., Haidian District, Beijing 100081, China. E-mail: renhe@cams.cma.gov.cn 6 2012, Meteorological Society of Japan above sea level and thus is also called ‘the roof of the world’, or ‘the third pole’. The Plateau is bounded on the east by the Hengduan Mountains, with the Himalaya Range bordering the south and west, and the Kunlun Mountains the north. Most part of the Plateau sits in the southwest part of China, including the Xizang Autonomous Region, Qinghai Province, the west part of Sichuan Province, the southern part of Xinjiang Uygur Autonomous Region, and parts of Gansu Province and Yunnan Province. Geographically, it also covers part of Bhutan, Nepal, India, Pakistan, Afghanistan, Tajikistan, and Kyrgyzstan. The Plateau occupies an area of 2.5 million square kilometers, with 2.4 million square kilometers standing within the territory of the People’s Republic of China. The Tibetan Plateau is a huge piece of land jutting out of the earth surface, stretching up to the middle troposphere. As a result, the temperature, humidity, air pressure and other meteorological elements over the Plateau are noticeably di¤erent from the ones in the surrounding free atmosphere. In the boreal summer, the Plateau is an immense heat source in the middle troposphere, and a cold source in the boreal winter (Ye and Gao 1979). Its thermal and dynamical e¤ects cast a major impact on the formation and evolution of atmospheric circulations and climate across China, Asia, and even the world (Ye et al. 1957, 1998; Huang 1985; Yanai et al. 1992). The vortex formed up above the Plateau and its eastward moving can produce a critical e¤ect on the heavy rains occurred in the east part of China. For example, an extraordinary heavy rain that attacked North China in 1963, and an extraordinary flush flood that swept across the Yangtze River valley in 1954 were associated with the eastbound movement of vortexes stemmed from the Plateau (Tao and Ding 1981). The dynamic and thermal e¤ects of the Plateau play a key role in the water vapor transportation to the Yangtze River valley during the Meiyu period in China (Xu et al. 2002). The Plateau’s sensible heat driven air pump (SHAP) e¤ect not only sustains the summer monsoons in Asia, but also a¤ects global climate by inducing up a Rossby wave train (Wu et al. 1997). The e¤ects of the latent heat as well as the sensible heat were also identified recently. Fujinami and Yasunari (2001) investigated seasonal variations in cloud activity over the Plateau, reporting significant cloud activity in spring (March–April). Ueda et al. (2003) also demonstrated the importance of condensation heating in the heat balance during the pre-onset phase of the summer monsoon over the western Plateau. The first intensive in situ observations during early spring upon the Plateau were performed in April 2004 under the framework of the Coordinated Enhanced Observing Period (CEOP) (Koike 2004). Based on in situ and satellite observations, and numerical simulations, Taniguchi and Koike (2007) reported the importance of cumulus activity in terms of increases in atmospheric temperature in the upper troposphere, even in April. In the boreal winter, the change of the heat source across the Plateau may breed out abnormal zonal winds over the equatorial Pacific Ocean, which in turn may result in an abnormal sea surface temperature that would eventually a¤ect ENSO events (Chen et al. 2001). In recent years, China has witnessed a raised frequency of meteorological disasters (China Meteorological Administration 2007). China has been working hard to establish a well functioned meteorological observing network, in an attempt to meet the needs of disaster prevention and reduction. However, the operational meteorological stations in the west part of the country are noticeably lower in number, compared with the east part (Zhang 2006). The number of the meteorological stations sitting across the Tibetan plateau, a region that takes up about one fourth of the nation’s territory, is extremely out of proportion to the vast area it has covered, due to high elevation, tough natural environment and di‰cult observation. The scarcity of the observed data over such a vast area not only compromises the scientific research, but also questions the reliability and accuracy of predictions of high impact weather events across the Plateau and the area to its east, the Yangtze River and Yellow River valleys and other East Asian countries, in particular. Taking into account the importance of the Tibetan Plateau in studying and predicting the evolution of weather and climate in China and in East Asia as well, it is necessary to improve the capability and utility of the atmospheric watch across ‘the roof of the world’ and its adjacent areas, and enhance China’s capabilities in severe weather prediction and disaster prevention and reduction. Considering the importance of establishing an integrated atmospheric observing system on the Tibetan Plateau, the joint observation and research on the Tibetan atmosphere between Chinese and Japanese governments were defined as one of key cooperation topics in December 1999. In July 2002, the Chinese Academy of Meteorological Sciences 2 Journal of the Meteorological Society of Japan Vol. 90C