叶面积指数(Leaf Area Index,LAI)是表征植被冠层结构的核心参数。在地面对LAI的间接测量是遥感反演算法验证和改进的重要手段,而目前基于Beer-Lambert定律的森林LAI地面间接测量方法存在着严重的低估问题。本文通过理论分析,指出Beer-L...叶面积指数(Leaf Area Index,LAI)是表征植被冠层结构的核心参数。在地面对LAI的间接测量是遥感反演算法验证和改进的重要手段,而目前基于Beer-Lambert定律的森林LAI地面间接测量方法存在着严重的低估问题。本文通过理论分析,指出Beer-Lambert定律在应用到森林叶面积指数测量时,LAI低估的根本原因来源于叶面积体密度、消光路径及叶倾角投影G函数在空间上的不均匀性,并定量评估了冠层非随机分布对LAI测量结果的影响,发现植被冠层的非随机分布会对LAI的测量带来20%～40%的误差。这一结论,对于Beer-Lambert定律的简单修正应用于森林LAI间接测量时仍存在着较大的局限性,尚未能根本上解决LAI的低估问题,故间接测量LAI的理论和方法需进一步深入研究。展开更多
The mean path length(MPL)of photons is a critical parameter to calculate tissue absorption coefficient as well as blood oxygenation using modified Beer-Lambert law,where in the differential path factor(DPF)is often as...The mean path length(MPL)of photons is a critical parameter to calculate tissue absorption coefficient as well as blood oxygenation using modified Beer-Lambert law,where in the differential path factor(DPF)is often assumed as constant over range of tissue absorption.By utilizing the Monte Carlo(MC)simulation of photon migrations in the leg,this study used four approaches to estimate MPL,and compared them with that determined by the MPL definition.The simulation results indicate that the DPF is remarkably affected by tissue absorption,at approximate 10% variation.A linear model is suggested to calculate MPL for measurements of tissue absorption as well as blood oxygenation using modified Beer-Lambert law.展开更多
文摘叶面积指数(Leaf Area Index,LAI)是表征植被冠层结构的核心参数。在地面对LAI的间接测量是遥感反演算法验证和改进的重要手段,而目前基于Beer-Lambert定律的森林LAI地面间接测量方法存在着严重的低估问题。本文通过理论分析,指出Beer-Lambert定律在应用到森林叶面积指数测量时,LAI低估的根本原因来源于叶面积体密度、消光路径及叶倾角投影G函数在空间上的不均匀性,并定量评估了冠层非随机分布对LAI测量结果的影响,发现植被冠层的非随机分布会对LAI的测量带来20%～40%的误差。这一结论,对于Beer-Lambert定律的简单修正应用于森林LAI间接测量时仍存在着较大的局限性,尚未能根本上解决LAI的低估问题,故间接测量LAI的理论和方法需进一步深入研究。
基金Research Funds from North University of China(No.130087)
文摘The mean path length(MPL)of photons is a critical parameter to calculate tissue absorption coefficient as well as blood oxygenation using modified Beer-Lambert law,where in the differential path factor(DPF)is often assumed as constant over range of tissue absorption.By utilizing the Monte Carlo(MC)simulation of photon migrations in the leg,this study used four approaches to estimate MPL,and compared them with that determined by the MPL definition.The simulation results indicate that the DPF is remarkably affected by tissue absorption,at approximate 10% variation.A linear model is suggested to calculate MPL for measurements of tissue absorption as well as blood oxygenation using modified Beer-Lambert law.
