RELATIONS BETWEEN EVAPORATION COEFFICIENTS AND VEGETATION INDEXES STUDIED BY MODEL SIMULATIONS
RELATIONS BETWEEN EVAPORATION COEFFICIENTS AND VEGETATION INDEXES STUDIED BY MODEL SIMULATIONS
复制标题
DOI：
10.1016/0034-4257(94)90090-6
复制
发表时间：
1994-10-01
影响因子：
13.5
通讯作者：
DAUGHTRY, CST
中科院分区：
文献类型：
--
作者：
CHOUDHURY, BJ;AHMED, NU;DAUGHTRY, CST
利用热量平衡和辐射传输模式计算了蒸发系数和植被指数之间的关系。蒸发系数为作物系数（定义为总蒸发量与参考作物蒸发量的比值）和蒸腾系数（定义为无胁迫蒸腾量与参考作物蒸发量的比值），植被指数为归一化差值、土壤调节植被指数和转换土壤调节植被指数。利用Priestley-Taylor方程计算了参考作物蒸发量。观测到的作物（小麦）的高度，叶面积指数和天气条件的变化，30天在凤凰城（亚利桑那州），连同不同类型的土壤在潮湿和干燥状态下的反射率，在模拟中使用。从模型计算的总蒸发量与蒸渗仪观测结果进行了比较。土壤蒸发量的变化会使作物系数与叶面积指数之间的关系产生较大的离散性，而蒸腾系数与叶面积指数之间的关系则离散性较小。对19种土壤类型在干湿条件下的30 d作物和气象数据以及反射率的模拟结果表明，蒸腾系数与植被指数之间存在显著的线性相关关系，土壤调节植被指数的解释方差（r2）最高（r2 = 0.88），归一化差异的解释方差（r2 = 0.81）最低。利用丛集植被模型研究了空间异质性对蒸腾系数与土壤调节植被指数之间关系的影响。这些模拟小麦蒸腾系数和植被指数之间的关系进行了讨论的背景下，来自几种作物和草的观测。本文的分析为利用遥感数据估算土壤蒸腾量提供了理论依据。
Calculations using a heat balance and a radiative transfer model have been done to study relations among evaporation coefficients and vegetation indices. The evaporation coefficients are the crop coefficient (defined as the ratio of total evaporation and reference crop evaporation) and the transpiration coefficient (defined as the ratio of unstressed transpiration and reference crop evaporation), while the vegetation indices considered in this study are the normalized difference, soil adjusted vegetation index, and transformed soil adjusted vegetation index. The reference crop evaporation has been calculated using the Priestley-Taylor equation. The observed variations of crop (wheat) height, leaf area index, and weather conditions for 30 days at Phoenix (Arizona), together with the reflectances of different types of soil in wet and dry states, are used in the simulation. The total evaporation calculated from the model compared well with lysimeter observations. Variations in soil evaporation can introduce considerable scatter in the relation between the crop coefficient and leaf area index, while this scatter is much less for the relation between transpiration coefficient and leaf area index. The simulation results for 30 days of crop and weather data and reflectances of 19 soil types in wet and dry conditions gave significant linear correlations between the transpiration coefficient and the vegetation indices, the explained variance (r2) being highest for the soil adjusted vegetation index (r2 = 0.88) and lowest for the normalized difference (r2 = 0.81). A clump vegetation model is used to address the effect of spatial heterogeneity on the relationship between the transpiration coefficient and soil adjusted vegetation index. These simulated relationships between transpiration coefficient and vegetation indices for wheat are discussed in the context of the relationships derived from observations for several crops and grasses. The present analysis provides a theoretical basis for estimating, transpiration from remotely sensed data.