The effect of the soil moisture heterogeneity on the spatially averaged evaporation at the permafrost plain area in Tibetan Plateau
Nozomu Hirose (1), Toshio Koike (2)
(1) Department of Civil and Environmental Engineering, Nagaoka University of Technology
(2) Department of Civil Engineering, University of Tokyo
Temporal variability of the Asian summer monsoon has been a key issue in understanding the global climate system.
The atmospheric heating over the Tibetan Plateau has been considered to play an important role on seasonal and internal change of the Asian summer monsoon.
Specifically, the impact of soil moisture and its distribution through energy and moisture transport on the atmosphere is one of important processes of land surface-to-atmosphere interaction.
Therefore we need to make a correct estimation of the spatial and temporal distribution of surface soil moisture and its effects on spatially averaged fluxes from land surface to atmosphere.
In this paper, we discuss the effect of the soil moisture heterogeneity on the spatially averaged evaporation in Tibetan Plateau.
Using the observational data obtained during the GAME/Tibet Intensive Observation Period (IOP) in 1998, the seasonal variability of the surface soil moisture distribution is shown in a 1km by 1km plain area. The water and energy flow processes in the permafrost region are studied with regard to the relationship between soil moisture and permafrost micro topography. Based on these processes, we developed and modified the 1-D heat and water flow model.
At first, this model is applied to the observation site at the center of the Tibetan Plateau.
The seasonal variability of surface soil moisture distribution is represented and good agreement with observed one using this model.
Secondly, to examine the effect of the soil moisture distribution, the spatially averaged evaporation calculated by this model is estimated using two methods. Two kinds of the spatially averaged evaporation are compared.
Consequently, this comparison indicates that it is important for the estimation of spatially averaged evaporation to consider the effects of soil moisture heterogeneity.
