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

Titelangaben

Gerken, Tobias ; Babel, Wolfgang ; Herzog, Michael ; Sun, Fanglin ; Ma, Yaoming ; Foken, Thomas ; Graf, Hans-F.:
High-resolution modelling of interactions between soil moisture and convective development in a mountain enclosed Tibetan Basin.
In: Hydrology and Earth System Sciences. Bd. 19 (2015) Heft 9 . - S. 4023-4040.
ISSN 1607-7938
DOI der Verlagsversion: https://doi.org/10.5194/hess-19-4023-2015

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Abstract

The Tibetan Plateau plays a significant role in at-mospheric circulation and the Asian monsoon system. Tur-bulent surface fluxes and the evolution of boundary-layerclouds to deep and moist convection provide a feedback sys-tem that modifies the plateau’s surface energy balance onscales that are currently unresolved in mesoscale models.This work analyses the land surface’s role and specificallythe influence of soil moisture on the triggering of convectionat a cross section of the Nam Co Lake basin, 150 km northof Lhasa using a cloud-resolving atmospheric model with afully coupled surface. The modelled turbulent fluxes and de-velopment of convection compare reasonably well with theobserved weather. The simulations span Bowen ratios of 0.5to 2.5. It is found that convective development is the strongestat intermediate soil moisture. Dry cases with soils close to thepermanent wilting point are moisture limited in convectivedevelopment, while convection in wet soil moisture casesis limited by cloud cover reducing incoming solar radiationand sensible heat fluxes, which has a strong impact on thesurface energy balance. This study also shows that local de-velopment of convection is an important mechanism for theupward transport of water vapour, which originates from thelake basin that can then be transported to dryer regions of theplateau. Both processes demonstrate the importance of soilmoisture and surface–atmosphere interactions on the energyand hydrological cycles of the Tibetan Plateau.