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China University (2013)

Simulation Research Of Land Surface Process Over Two Typical Underlying Covers In The Arid And Semi-arid Areas

Yang Q D

Titre : Simulation Research Of Land Surface Process Over Two Typical Underlying Covers In The Arid And Semi-arid Areas

Auteur : Yang Q D

Grade : Doctoral Dissertation 2013

Université : China University

Résumé partiel
The arid and semi-arid regions are nearly40%of the global land area, its surface cover are diverse and complex, including various landscapes such as grassland, farmland, desert, Gobi, and permafrost. For these complicated underlying surface, their characteristics of land surface process varies with area and season obviously, and is significantly affected by natural changes and the changes of land use and land cover which is caused by the human activities, and thus their land surface process plays a very important role in the global climate system. But for the most of present land surface process models, there is still existence of a large deviation in land surface process simulation over the typical underlying surface in the arid and semi-arid areas. Furthermore, there is the energy imbalance in the surface layer in observation experiment ; this makes the land surface process simulation more difficult. How to improve the land surface parameterization schemes, and develop land surface process model more applicable to the arid and semi-arid regions is an important task in the study of land surface processes.In order to improve the performance of land surface model simulation over the typical underlying surface in the arid and semi-arid areas, the land surface model was studied from three aspects in this paper. Firstly, a land surface process model TBLSHAW was developed and verified with the observation data in the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL). Secondly, focusing on the influence of the energy imbalance, which was commonly existed in the land surface observation experiment, the impact of energy imbalance upon land surface process simulation in semi-arid region were studied by using the SACOL surface layer observation data and land surface model TBLSHAW. Finally, in view of the fact that the large number of arid areas surface was covered by plastic mulch to inhibit evaporation, a new model TBLSHAW_MULCH was developed by improving the parameterization scheme with the observation at a cropland underlying surface covered by plastic mulch in the Gulang Heterogeneous Underlying Surface Layer Experiment (GHUSLE) in the arid region to simulate the land surface process of the cropland underlying covered by plastic mulch in arid region. We draw the following conclusions :(1) Based on the energy and material balance principle between land surface and atmosphere, a land surface model TBLSHAW was developed by means of SHAW and CoLM models. The TBLSHAW model, which was a land surface model including soil-vegetation-atmosphere interactions, absorbed the two-big-leaf model to calculate the material and energy balance between the vegetation and the atmosphere and to consider the vegetation canopy radiation transfer, precipitation interception, evaporation, transpiration, photosynthesis and other physical processes in detail ; It used the general soil heat and water coupling transfer model to calculate soil moisture and temperature, and included the process of soil freezing and thawing, evaporation and precipitation infiltration ; It combined part of the land surface parameterization schemes which was developed using the long-term observations of soil temperature and moisture and surface layer at SACOL ; and it employed SHAW model framework.(2) Using observational data in SACOL, the performance of the TBLSHAW model was verified by simulating the land surface process of the typical dry (bare soil), wet season (grass land), freezing and thawing. Comparing among the observation and the simulations by TBLSHAW and different land surface process models, the results indicated that TBLSHAW model improved the simulation of soil water and heat transfer process in SCAOL.

Mots clés : arid and semi-arid region, land surface process, energy imbalance in the surface layer, SACOL, plastic mulch, GHUSLE

Présentation (Globethesis)

Page publiée le 21 avril 2013, mise à jour le 10 janvier 2018