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Tsinghua University (2008)

Vegetation Parameter and Evaporation Estimation Based on Remote Sensing for Assessing Regional Drought

Yi Yong Hong

Titre : Vegetation Parameter and Evaporation Estimation Based on Remote Sensing for Assessing Regional Drought

Auteur : Yi Yong Hong

Grade : Doctoral Dissertation 2008

Université : Tsinghua University

The water shortage has become the major factors restricting China’s social economy, especially the agricultural development, rational use and optimize the allocation of limited water resources, water law requires in-depth study crops and keep abreast of the crop drought. Traditional field observation method due to the underlying surface complexity difficult to regional expansion, and remote sensing with spatial continuity and temporal dynamics characteristics, regional water consumption and drought assessment has broad application prospects. This article using MODIS vegetation parameters inversion and regional evapotranspiration estimation methods and models have been studied, and on this basis to explore the application of remote sensing in the assessment of farmland and water shortage and drought. The paper first analyzes the different MODIS reflectance data sets uncertainty, and this uncertainty vegetation parameters inversion results by the two methods of vegetation index and radiative transfer model analysis. Findings : relatively Collection 4 (C4) of Japanese reflectance data, Data Collection 5 (C5) improved significantly reduce the uncertainty of the reflectance in the visible and near-infrared bands, the uncertainty of the data phase synthesis of the C4 also significantly reduced, according to the results of both data inversion of vegetation parameters more reliable. On this basis, the use of phase synthesis of MODIS data vegetation parameters inversion methods, remote sensing single-layer model and the two-layer model combined Weishan Irrigation District surface water heat flux observations of these two models a comparative study. Solving for the two-layer model, a new component of flux initialization method based on the definition of the surface impedance the Penman formula vegetation component MODIS LAI evapotranspiration, by comparison with ground observations simulation results of the method is better than the usual double-layer model is initialized with Priestley-Taylor equation. The study also found that two-layer model is very sensitive to the input parameters in the temperature difference is small, and large areas of vegetation coverage, the two-tier model simulation results are not better than the single-layer model. This paper also studied the assimilation of land surface process model and remote sensing methods. Preliminary results show that : the initial soil moisture error is relatively large, the assimilation of soil moisture observations can effectively improve the accuracy of the model simulated soil moisture using MODIS land surface temperature assimilation can effectively improve the simulation results of the surface heat flux, description of land face the process of assimilation model has a large potential for regional hydrothermal circulation and drought assessment application. Finally, the use of crop water stress index CWSI based on the of actual evapotranspiration definition of remote sensing inversion temperature Vegetation Drought Index Application of TVDI in based vegetation index and surface temperature Weishan Irrigation District Winter 2005-2007 water shortage and the 2006 Sichuan East and Chongqing drought assessment. Verify the results on the ground that the CWSI is not local climatic conditions and crop growth change, a more reasonable assessment of drought.

Mots clés : MODIS data Vegetation parameters Regional evapotranspiration Land surface model Drought assessment

Présentation (Dissertationtopic)

Page publiée le 3 mai 2013, mise à jour le 10 janvier 2018