青藏高原地气耦合系统及其天气气候效应:第三次青藏高原大气科学试验

The Tibetan Plateau surface-atmosphere coupling system and its weather and climate effects:The Third Tibetan Plateau Atmospheric Scientific Experiment

由于青藏高原(简称高原)是影响中国极端天气和气候事件的关键区,对天气、气候预报有重要影响。因此,中国气象局、国家自然科学基金委员会、中国科学院共同推动了"第三次青藏高原大气科学试验(TIPEX-Ⅲ)"工作。自2013年的预试验开始, TIPEX-Ⅲ在高原西部狮泉河、改则和申扎新建全自动探空系统,填补了高原西部缺少常规探空站的空白;在高原中、西部建成土壤温、湿度观测网;实施了高原尺度和那曲区域尺度的边界层观测,那曲多型雷达和机载设备的云降水物理特征综合观测,高原多站的对流层-平流层大气成分观测。在研究成果方面,项目结果指出,在高原中、西部草原、草甸和裸土下垫面状况下地表热量湍流交换系数和感热通量明显低于过去较早的估计值;高原主体的对流云活动主要不是来自南亚季风区的向北传播,而可能是局地发展所致;揭示出那曲对流云日变化特征、云宏微观特征以及云中水不同相态之间的转化机制,提出了夏季高原加热在维持亚洲大气"水塔"中的作用,以及高原加热对亚洲、非洲、北美洲气候的调节作用。在数值预报模式中,Γ分布比M-P分布更适合于高原雨滴谱特征,通过改进高原热传导过程参数化方案可以降低模式中高估的地表感热,并提升模式对中国中、东部雨带的模拟能力;此外,考虑青藏高原关键区信号可以提升中国中、东部降水的预报技巧。TIPEX-Ⅲ还带动了地面和高空常规观测、天气业务雷达和风廓线雷达等观测数据加工处理业务技术的发展,提升了中国国家级土壤湿度、水汽含量等遥感产品和高分辨率多源降水融合产品的质量,促进了气象监测、预报和数据共享业务的发展。

The Tibetan Plateau(TP) is a key area affecting extreme weather and climate events and related weather and climate forecasting in China. The China Meteorological Administration(CMA), the National Natural Scientific Foundation of China, and the Chinese Academy of Sciences jointly initiated the Third Tibetan Plateau Atmospheric Scientific Experiment(TIPEX-Ⅲ). Since the preliminary experiment conducted in 2013, routine automatic sounding systems have been newly deployed at Shiquanhe, Gaize and Shenzha stations during the TIPEX-Ⅲ, which fills the gap of routine operational sounding stations lacked over the western TP. Observational networks for soil temperature and moisture in the central and western TP have also been established. Meanwhile, the TIPEX-Ⅲ also conducted plateau-and regional-scale boundary-layer observations, measured cloud-precipitation microphysical characteristics by multiple radars and aircraft campaigns, and collected tropospheric-stratospheric atmospheric composition at multiple sites. The research results of the TIPEX-Ⅲ show that the surface turbulent heat exchange coefficient and sensible heat flux are remarkably lower than the earlier estimations at grassland, meadow and bare soil surfaces of the central and western TP. Climatologically, cumulus clouds over the main body of the TP might develop locally instead of originating from cumulus clouds that propagate northward from South Asia. The TIPEX-Ⅲ reveals diurnal variations of cumulus cloud, macro-and micro-physical characteristics of cloud and mechanisms for the transition between different water phases in clouds, proposes a maintenance mechanism responsible for the Asian "atmospheric water tower", and explores the effects of the TP heating anomalies on Asian, African, and North American climates. In the numerical forecast models, it is found that the Γ raindrop size distribution is more suitable for the TP characteristics compared to the M-P distribution, and modifying the parametrization scheme of heat transfer processes over the TP can reduce the overestimation of simulated sensible heat, which may further improve the skill for rain belt simulation in central and eastern parts of China. Considering climatic signals in some key areas of the TP can also improve the skill for rainfall forecast in the central and eastern parts of China. Moreover, the TIPEX-Ⅲ promotes the development of operational technology in processing surface observations, soundings, and radar observations, improves the quality of satellite remote sensing soil moisture and atmospheric water vapor content products as well as high-resolution gauge-radar-satellite merged rainfall products, and promotes the development of meteorological monitoring, forecast, and data sharing operations.