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Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
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Volume 19, issue 9 | Copyright
Hydrol. Earth Syst. Sci., 19, 4023-4040, 2015
https://doi.org/10.5194/hess-19-4023-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 29 Sep 2015

Research article | 29 Sep 2015

High-resolution modelling of interactions between soil moisture and convective development in a mountain enclosed Tibetan Basin

T. Gerken1,2,a, W. Babel1, M. Herzog2, K. Fuchs1,b, F. Sun3, Y. Ma4, T. Foken1,5, and H.-F. Graf2 T. Gerken et al.
  • 1Department of Micrometeorology, University of Bayreuth, Bayreuth, Germany
  • 2Centre for Atmospheric Science, Department of Geography, University of Cambridge, Cambridge, UK
  • 3Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou, China
  • 4Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, CAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing, China
  • 5Member of Bayreuth Center of Ecology and Environment Research (BayCEER), Bayreuth, Germany
  • anow at: Department of Meteorology, The Pennsylvania State University, University Park, PA, USA
  • bnow at: Institute of Agricultural Science, ETH Zürich, Zurich, Switzerland

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.

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Surface moisture is an important control for the development of clouds and precipitation on the Tibetan Plateau. While dry surface conditions do not provided enough water for the development of precipitation and convection, wet surface conditions lead to increased cloud cover and a decrease in solar irradiation, which also reduces convection development. It was found that intermediate soil moistures are associated with the strongest convection.
Surface moisture is an important control for the development of clouds and precipitation on the...
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