干旱区生态环境知识资源中心(Arid): Time-variations of zeroth-order vegetation absorption and scattering at L-band

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DOI	10.1016/j.rse.2021.112726
	Time-variations of zeroth-order vegetation absorption and scattering at L-band
	Baur, Martin J.; Jagdhuber, Thomas; Feldman, Andrew F.; Chaparro, David; Piles, Maria; Entekhabi, Dara
通讯作者	Baur, MJ (corresponding author), Univ Cambridge, Dept Geog, Downing Pl, Cambridge CB2 3EN, England.
来源期刊	REMOTE SENSING OF ENVIRONMENT
ISSN	0034-4257
EISSN	1879-0704
出版年	2021
卷号	267
英文摘要	Surface soil moisture and vegetation optical depth (VOD), as an indicator of vegetation wet biomass, from passive microwave remote sensing have been increasingly applied in global ecology and climate research. Both soil moisture and VOD are retrieved from satellite brightness temperature measurements assuming a zeroth order radiative transfer model, commonly known as the tau-omega model. In this model the emission of a vegetated surface is dependent on soil moisture, vegetation absorption and vegetation scattering. Vegetation scattering is normally represented by the single scattering albedo, omega, and is commonly assumed to be a time-invariant calibration parameter to achieve high accuracy in soil moisture estimation. Therefore, little is known about omega dynamics in the context of its ecological information content. Furthermore, VOD and omega are functions of more fundamental absorption and scattering coefficients kappa(a) and kappa(s). In this study, we retrieve both VOD and omega as well as kappa(a) and kappa(s) in two separate tau-omega model frameworks using known soil moisture information. Our sensitivity analysis confirms that vegetation attenuation has a strong impact on the sensitivity of the retrieval to noise. If vegetation attenuation approaches zero, omega is weakly constrained, which leads to strong w dynamics. If vegetation attenuation is very high, VOD, kappa(a) and kappa(s) are increasingly less constrained and susceptible to noise, while omega becomes quasi time-invariant. Coinciding with our sensitivity study, global retrievals from SMAP brightness temperatures exhibit large omega dynamics in drylands and deserts, decreasing rapidly with increasing vegetation cover. In drylands omega might peak during the dry season at the seasonal VOD minimum. With increasing vegetation attenuation, omega dynamics start to follow leaf phenology before they transition to a nearly time-invariant omega in forested areas. VOD, kappa(a) and kappa(s) follow the dynamics of wet biomass and peak after the maximum of leaf area index and precipitation. Our results suggest that zeroth order scattering is generally time-invariant over a majority of the global vegetated areas. In general, time dynamic omega and kappa(s) might provide additional information on the state of the vegetation canopy, which can be valuable for biosphere studies and relevant for the parameterization of vegetation scattering in soil moisture retrievals.
英文关键词	Relative canopy absorption Relative canopy scattering Vegetation optical depth Effective scattering albedo SMAP ICESat 2 Lidar
类型	Article
语种	英语
收录类别	SCI-E
WOS记录号	WOS:000708550700004
WOS关键词	RADIATIVE-TRANSFER MODEL ; OPTICAL DEPTH ; SOIL-MOISTURE ; MICROWAVE EMISSION ; ALBEDO ; RETRIEVAL ; SMOS ; PARAMETERS ; FORESTS ; POLARIZATION
WOS类目	Environmental Sciences ; Remote Sensing ; Imaging Science & Photographic Technology
WOS研究方向	Environmental Sciences & Ecology ; Remote Sensing ; Imaging Science & Photographic Technology
资源类型	期刊论文
条目标识符	http://119.78.100.177/qdio/handle/2XILL650/364503
作者单位	[Baur, Martin J.] Univ Cambridge, Dept Geog, Downing Pl, Cambridge CB2 3EN, England; [Jagdhuber, Thomas] German Aerosp Ctr, Microwaves & Radar Inst, Munchener Str 20, D-82234 Wessling, Germany; [Jagdhuber, Thomas] Augsburg Univ, Inst Geog, Alter Postweg 118, D-86159 Augsburg, Germany; [Feldman, Andrew F.; Entekhabi, Dara] MIT, Dept Civil & Environm Engn, 77 Massachusetts Ave, Cambridge, MA 02139 USA; [Chaparro, David] Univ Politecn Cataluna, Remote Sensing Lab, Barcelona, Catalunya, Spain; [Piles, Maria] Univ Valencia, Image Proc Lab, Valencia, Spain
推荐引用方式 GB/T 7714	Baur, Martin J.,Jagdhuber, Thomas,Feldman, Andrew F.,et al. Time-variations of zeroth-order vegetation absorption and scattering at L-band[J],2021,267.
APA	Baur, Martin J.,Jagdhuber, Thomas,Feldman, Andrew F.,Chaparro, David,Piles, Maria,&Entekhabi, Dara.(2021).Time-variations of zeroth-order vegetation absorption and scattering at L-band.REMOTE SENSING OF ENVIRONMENT,267.
MLA	Baur, Martin J.,et al."Time-variations of zeroth-order vegetation absorption and scattering at L-band".REMOTE SENSING OF ENVIRONMENT 267(2021).