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DOI	10.5194/essd-13-2819-2021
	Year-long, broad-band, microwave backscatter observations of an alpine meadow over the Tibetan Plateau with a ground-based scatterometer
	Hofste, Jan G.; van der Velde, Rogier; Wen, Jun; Wang, Xin; Wang, Zuoliang; Zheng, Donghai; van der Tol, Christiaan; Su, Zhongbo
通讯作者	Hofste, JG (通讯作者)，Univ Twente, Fac Geoinformat Sci & Earth Observat ITC, Enschede, Netherlands.
发表日期	2021
ISSN	1866-3508
EISSN	1866-3516
起始页码	2819
结束页码	2856
卷号	13 期号:6
英文摘要	A ground-based scatterometer was installed on an alpine meadow over the Tibetan Plateau to study the soil moisture and temperature dynamics of the top soil layer and air-soil interface during the period August 2017-August 2018. The deployed system measured the amplitude and phase of the ground surface radar return at hourly and half-hourly intervals over 1-10 GHz in the four linear polarization combinations (vv, hh, hv, vh). In this paper we describe the developed scatterometer system, gathered datasets, retrieval method for the backscattering coefficient (sigma(0)), and results of sigma(0). The system was installed on a 5m high tower and designed using only commercially available components: a vector network analyser (VNA), four coaxial cables, and two dual-polarization broad-band gain horn antennas at a fixed position and orientation. We provide a detailed description on how to retrieve the backscattering coefficients for all four linear polarization combinations sigma(0)(pq), where p is the received and q the transmitted polarization (v or h), for this specific scatterometer design. To account for the particular effects caused by wide antenna radiation patterns (G) at lower frequencies, sigma(0) was calculated using the narrow-beam approximation combined with a mapping of the function G(2)/R-4 over the ground surface. (R is the distance between antennas and the infinitesimal patches of ground surface.) This approach allowed for a proper derivation of footprint positions and areas, as well as incidence angle ranges. The frequency averaging technique was used to reduce the effects of fading on the sigma(0)(pq) uncertainty. Absolute calibration of the scatterometer was achieved with measurements of a rectangular metal plate and rotated dihedral metal reflectors as reference targets. In the retrieved time series of sigma(0)(pq) for L-band (1.5-1.75 GHz), S-band (2.5-3.0 GHz), C-band (4.5-5.0 GHz), and X-band (9.0-10.0 GHz), we observed characteristic changes or features that can be attributed to seasonal or diurnal changes in the soil: for example a fully frozen top soil, diurnal freeze-thaw changes in the top soil, emerging vegetation in spring, and drying of soil. Our preliminary analysis of the collected sigma(0)(pq) time-series dataset demonstrates that it contains valuable information on water and energy exchange directly below the air-soil interface - information which is difficult to quantify, at that particular position, with in situ measurement techniques alone. Availability of backscattering data for multiple frequency bands (raw radar return and retrieved sigma(0)(pq)) allows for studying scattering effects at different depths within the soil and vegetation canopy during the spring and summer periods. Hence further investigation of this scatterometer dataset provides an opportunity to gain new insights in hydrometeorological processes, such as freezing and thawing, and how these can be monitored with multi-frequency scatterometer observations. The dataset is available via https://doi.org/10.17026/dans-zfb-qegy (Hofste et al., 2021). Software code for processing the data and retrieving sigma(0)(pq) via the method presented in this paper can be found under https://doi.org/10.17026/dans-xyf-fmkk (Hofste, 2021).
关键词	RADAR CROSS-SECTION SOIL-MOISTURE SCATTERING MODEL PARAMETERS SYSTEM DEPTH
语种	英语
WOS研究方向	Geology ; Meteorology & Atmospheric Sciences
WOS类目	Geosciences, Multidisciplinary ; Meteorology & Atmospheric Sciences
WOS记录号	WOS:000663940200002
来源期刊	EARTH SYSTEM SCIENCE DATA
来源机构	中国科学院西北生态环境资源研究院
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/255013
作者单位	[Hofste, Jan G.; van der Velde, Rogier; van der Tol, Christiaan; Su, Zhongbo] Univ Twente, Fac Geoinformat Sci & Earth Observat ITC, Enschede, Netherlands; [Wen, Jun] Chengdu Univ Informat Technol, Plateau Atmosphere & Environm Key Lab Sichuan Pro, Coll Atmospher Sci, Chengdu, Peoples R China; [Wang, Xin; Wang, Zuoliang] Chinese Acad Sci, Northwest Inst Ecoenvironm & Resources, Key Lab Land Surface Proc & Climate Change Cold R, Lanzhou, Peoples R China; [Zheng, Donghai] Chinese Acad Sci, Natl Tibetan Plateau Data Ctr Inst Tibetan Platea, Beijing, Peoples R China
推荐引用方式 GB/T 7714	Hofste, Jan G.,van der Velde, Rogier,Wen, Jun,et al. Year-long, broad-band, microwave backscatter observations of an alpine meadow over the Tibetan Plateau with a ground-based scatterometer[J]. 中国科学院西北生态环境资源研究院,2021,13(6).
APA	Hofste, Jan G..,van der Velde, Rogier.,Wen, Jun.,Wang, Xin.,Wang, Zuoliang.,...&Su, Zhongbo.(2021).Year-long, broad-band, microwave backscatter observations of an alpine meadow over the Tibetan Plateau with a ground-based scatterometer.EARTH SYSTEM SCIENCE DATA,13(6).
MLA	Hofste, Jan G.,et al."Year-long, broad-band, microwave backscatter observations of an alpine meadow over the Tibetan Plateau with a ground-based scatterometer".EARTH SYSTEM SCIENCE DATA 13.6(2021).