"Tau-Omega"- and Two-Stream Emission Models Used for Passive L-Band Retrievals: Application to Close-Range Measurements over a Forest
"Tau-Omega"- and Two-Stream Emission Models Used for Passive L-Band Retrievals: Application to Close-Range Measurements over a Forest
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DOI：
10.3390/rs10121868
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发表时间：
2018-12-01
期刊：
影响因子：
5
通讯作者：
Matzler, Christian
中科院分区：
文献类型：
--
作者：
Schwank, Mike;Naderpour, Reza;Matzler, Christian
微波发射模型（EM）用于反演算法中，以根据在水平和垂直偏振p = {H，V}下在最低点角θ处测量的亮度温度T-B（p，θ）来估计地球物理状态参数，诸如土壤含水量（WC）和植被光学深度（τ）。适合于在检索算法中实现的EM必须捕获T-B（p，theta）对检索参数的响应，并且EM参数必须是实验上可访问的并且代表测量足迹。本研究的目的是探索的好处，多散射双流（2S）EM的“τ-欧米茄”（TO）EM被视为“参考”，以检索WC和τ从L波段T-B（p，θ）。对于稀疏和低散射植被T-B，EM = {TO，2S}模拟的EM（p，θ）收敛。对于密集和强烈分散的植被，情况并非如此。双参数（2 P）反演2 P（RC）=（WCRC，tau（RC））是从与TO EM合成的高程扫描T-B（p，theta j）= T-B，TO（p，theta j）以及从落叶林内的塔测量的T-B（p，theta j）计算的。反演反演（RC）采用EM = TO或EM = 2S，并假设固定的散射曲率。使用2S RC获得的WCRC比使用“参考”TO RC获得的WCRC略低（类似于1 m（3）m（-3）），而使用2S EM而不是TO EM时，tau（RC）显著降低。我们的研究概述了一些优点的2S EM在TO EM目前实施的业务SMOS和SMAP检索算法。
Microwave Emission Models (EM) are used in retrieval algorithms to estimate geophysical state parameters such as soil Water Content (WC) and vegetation optical depth (tau), from brightness temperatures T-B(p,theta) measured at nadir angles theta at Horizontal and Vertical polarizations p = {H,V}. An EM adequate for implementation in a retrieval algorithm must capture the responses of T-B(p,theta) to the retrieval parameters, and the EM parameters must be experimentally accessible and representative of the measurement footprint. The objective of this study is to explore the benefits of the multiple-scattering Two-Stream (2S) EM over the "Tau-Omega" (TO) EM considered as the "reference" to retrieve WC and tau from L-band T-B(p,theta). For sparse and low-scattering vegetation T-B,EM(p,theta) simulated with EM = {TO, 2S} converge. This is not the case for dense and strongly scattering vegetation. Two-Parameter (2P) retrievals 2P(RC) = (WCRC, tau(RC)) are computed from elevation scans T-B(p,theta j) = T-B,TO(p,theta j) synthesized with TO EM and from T-B(p,theta j) measured from a tower within a deciduous forest. Retrieval Configurations (RC) employ either EM = TO or EM = 2S and assume fixed scattering albedos. WCRC achieved with the 2S RC is marginally lower (similar to 1 m(3)m(-3)) than if achieved with the "reference" TO RC, while tau(RC) is reduced considerably when using 2S EM instead of TO EM. Our study outlines a number of advantages of the 2S EM over the TO EM currently implemented in the operational SMOS and SMAP retrieval algorithms.