Abstract
Abstract. 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.
Highlights
The Tibetan Plateau has an average elevation of more than 4500 m and is the world’s largest mountain highland
We start the analysis by comparing the convective development for case 2.0 × field capacity (FC) between the 2-D and 3-D simulations
Turbulent fluxes are highly variable on the Tibetan Plateau and, are important for the Bowen ratio and the surface energy balance, and have an effect on atmospheric dynamics
Summary
The Tibetan Plateau has an average elevation of more than 4500 m and is the world’s largest mountain highland. Land use/land cover change, such as permafrost (Cheng and Wu, 2007) and grassland degradation or deforestation (Cui and Graf, 2009; Cui et al, 2006), and effects on the carbon and hydrological cycles (Babel et al, 2014), are associated with overuse of resources and climate change. They affect atmospheric circulation and hydrological resources of the Tibetan Plateau, especially the cryosphere It is important to gain a better understanding of the hydrological processes in the region
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