High-resolution modelling of interactions between soil moisture and convective development in a mountain enclosed Tibetan Basin
High-resolution modelling of interactions between soil moisture and convective development in a mountain enclosed Tibetan Basin
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DOI：
10.5194/hess-19-4023-2015
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发表时间：
2015-09
影响因子：
6.3
通讯作者：
T. Gerken;W. Babel;M. Herzog;K. Fuchs;F. Sun;Yaoming Ma;T. Foken;H. Graf
中科院分区：
文献类型：
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作者：
T. Gerken;W. Babel;M. Herzog;K. Fuchs;F. Sun;Yaoming Ma;T. Foken;H. Graf
青藏高原在大气环流和亚洲季风系统中起着重要的作用。湍流表面通量和边界层云的演变，深和潮湿的对流提供了一个反馈系统，修改高原的表面能量平衡的尺度上，目前尚未解决的中尺度模型。这项工作分析了陆面的作用，特别是土壤水分对触发对流的横截面的纳木错湖流域，拉萨以北150公里，使用云解析大气模式与完全耦合的表面的影响。模拟的湍流通量和对流发展与观测到的天气相当吻合。模拟范围为0.5至2.5的Bowen比率。结果表明，在中等土壤湿度下对流发展最强。干燥的情况下，土壤接近永久萎蔫点的水分限制在对流发展，而对流在潮湿的土壤水分的情况下是有限的云层覆盖减少传入的太阳辐射和感热通量，这对地表能量平衡有很大的影响。这项研究还表明，对流的局部发展是水汽向上输送的一个重要机制，水汽来自湖盆，然后可以输送到高原的干燥地区。这两个过程表明，土壤水分和地表-大气相互作用的能量和青藏高原的水文循环的重要性。
The Tibetan Plateau plays a significant role in atmospheric circulation and the Asian monsoon system. Turbulent surface fluxes and the evolution of boundary-layer clouds to deep and moist convection provide a feedback system that modifies the plateau's surface energy balance on scales that are currently unresolved in mesoscale models. This work analyses the land surface's role and specifically the influence of soil moisture on the triggering of convection at a cross section of the Nam Co Lake basin, 150 km north of Lhasa using a cloud-resolving atmospheric model with a fully coupled surface. The modelled turbulent fluxes and development of convection compare reasonably well with the observed weather. The simulations span Bowen ratios of 0.5 to 2.5. It is found that convective development is the strongest at intermediate soil moisture. Dry cases with soils close to the permanent wilting point are moisture limited in convective development, while convection in wet soil moisture cases is limited by cloud cover reducing incoming solar radiation and sensible heat fluxes, which has a strong impact on the surface energy balance. This study also shows that local development of convection is an important mechanism for the upward transport of water vapour, which originates from the lake basin that can then be transported to dryer regions of the plateau. Both processes demonstrate the importance of soil moisture and surface–atmosphere interactions on the energy and hydrological cycles of the Tibetan Plateau.