青藏高原大气科学试验研究进展

该文对半个世纪以来, 我国气象工作者在青藏高原研究, 特别是1979年和1998年两次大规模青藏高原大气科学试验科学成果进行了全面回顾, 给出近年来青藏高原研究许多有重要价值的研究成果, 可概要地归纳为以下几个方面:两次青藏高原大气科学试验在青藏高原边界层研究、对流特征研究方面取得新进展, 发现许多新的观测事实。证明青藏高原也可能是低频振荡源地。试验发现青藏高原摩擦层风的Ekman螺线及热力混合层特征, 发现青藏高原上对流边界层高度可达2200 m, 湍流边界层高度比平原地区明显偏高; 研究给出了青藏高原近地层与边界层动力、热力结构及其湍流、对流云特征可构成青藏高原地区边界层的综合物理图像。追踪分析研究发现, 连续成串从青藏高原中部或东部发生、发展的对流云团族呈显著东移的特征, 认为长江暴雨洪水的初始对流云系统可追溯到青藏高原; 研究发现, 在适当的云天条件下, 在青藏高原上可观测到极大的太阳总辐射、有效辐射和地表净辐射。青藏高原地面反照率的变化产生热源、热汇的区域影响效应, 这种源汇带来季节性和区域性的变化将进一步影响到大气中长波波形的季节尺度变化, 研究还强调指出青藏高原雪盖的年度变化的反馈作用表现对行星尺度环流特征的影响, 在热带洋面也产生对SST异常的相互作用与影响; 青藏高原与亚洲季风系统影响研究取得显著进展; 研究发现, 青藏高原“感热气泵” (SHAP) 的有效工作导致了青藏高原地区由冬到夏大气环流的突变及南亚高压的突然北跳, 并维持着亚洲季风期; 研究揭示出青藏高原周边“大三角”区域是影响我国长江中下游暴雨的水汽输送关键区, 揭示在青藏高原地区及其东部水汽输送的“转运站”特征。水汽流向东的“转运”效应对长江梅雨期洪涝形成甚为重要; 青藏高原大气物质输送及其臭氧异常特征研究取得进展, 研究发现夏季在青藏高原上大气臭氧总量有一明显的低值中心存在, 并且发现拉萨的臭氧递减趋势比我国东部同纬度地区大, 而拉萨位于青藏高原臭氧低值中心的区域。

Advances of the Study on Tibetan Plateau Experiment of Atmospheric Sciences

A review of the research work on Tibetan Plateau for the recent 50 years is given.Especially,the important results for the first atmospheric science experiment on Tibetan Plateau in 1979(QXPMEX) and the second one in 1998(TIPEX) are suggested.It is found the long-frenquency oscillation which is inherent in Tibet Plateau tropospheric circulation and marked by out-ward propagation and the characteristics of Ekman spiral of PBL can be seen over Tibetan Plateau.The height of PBL is found to be as high as 2200 m over Tibetan Plateau,it is much higher than those in the plain areas.Dynamic and thermodynamic structures,as well as the characteristics of turbulence and convective clouds in the Plateau are discussed.A comprehensive physical pattern of convective structure of PBL is also given.It is found that under the condition of proper cloud cover,extremely high values of global solar radiation,effective radiation and surface net radiation are measured and the rain storm and flooding associated with the initial convective cloud system can be tracked to the Tibetan Plateau area.The regional impacts of heat source and heat sink associated with changes of the surface albedo over Tibetan Plateau are discussed.And the seasonal scale change of mid-long wave in the atmosphere is under the influence of the regional and seasonal change that is brought by the heat source and sink.The feedback of annual scale change of snow cover on the Tibetan Plateau is also emphasized in the research result,it shows that the planetary scale circulation on the Tibetan Plateau,the anomaly of SST and their interactions can be influenced by the snow cover.There are remarkable evolutions of the interactions of Tibetan Plateau and Asian monsoon.It is found that the availability of sensitive heat pump(SHAP) induces the abrupt air circulation from winter to summer and the South Asian High jump to the north,and maintains the period of the monsoon.It is found that Tibetan Plateau and its eastern areas "large triangle" are key areas for the transportation of water vapor flow.It is a very important rule to form the rain storm and the flooding in the Yangtze River during Meiyu period.The characteristics of matter transfer and ozone anomaly on Tibetan Plateau are found.There is a low value center of ozone on Tibetan Plateau in summer and the descending trend of ozone in Lhasa is notable than that of the east of China at the same latitude.Lhasa locates in the areas of ozone low value center.