Abstract
Temperature Vegetation Dryness Index (TVDI) is widely used in soil moisture estimation for its simplicity and convenient data access. Although the factors that affect the Ts-NDVI space from which the TVDI is derived is widely discussed, little work has been done in lessening the affections in the quantitative derivation. In this study, considering the geographical characteristics in China, the affection of lapse rate on soil moisture estimation is discussed. An approach of correcting Ts with DEM before constructing Ts-NDVI space is tried to lessen the lapse rate affection. Lapse rate is used in the correction and measured topsoil moisture from around China is used to confirm the parameter in the correction. Compare between TVDI obtained before and after the correction shows that TVDI obtained after correction do better reflect the soil moisture status in China. Ⅰ. INTRODUCTIONS Soil moisture condition is an important index in evaluating environmental conditions related to ecological, hydrological, and atmospheric processes. Considerable researches have been done in soil moisture estimation. Among these, TVDI, for its simplicity and convenient data access, is widely used. TVDI is derived from Ts-NDVI space. The location of a pixel in the Ts-NDVI space is influenced by many factors, a number of studies have been done on this(1-3). Based on findings in the literature, the suggested affecting factors include fractional vegetation cover, evapotranspiration, thermal properties of the surface, net radiation, atmospheric forcing and surface roughness etc. These factors have certain influences on near surface energy balance, thus affect Ts. In this study, the energy balance model is explored together with
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