DOI: 10.5194/hess-21-4767-2017
Scopus记录号: 2-s2.0-85030106604
论文题名: Use of reflected GNSS SNR data to retrieve either soil moisture or vegetation height from a wheat crop
作者: Zhang S ; , Roussel N ; , Boniface K ; , Cuong Ha M ; , Frappart F ; , Darrozes J ; , Baup F ; , Calvet J ; -C
刊名: Hydrology and Earth System Sciences
ISSN: 10275606
出版年: 2017
卷: 21, 期: 9 起始页码: 4767
结束页码: 4784
语种: 英语
Scopus关键词: Agriculture
; Antennas
; Biomass
; Crops
; Ecology
; Global positioning system
; Least squares approximations
; Moisture
; Satellite antennas
; Soil moisture
; Soil surveys
; Soils
; Surface measurement
; Vegetation
; Wavelet analysis
; Accurate estimation
; Global Navigation Satellite Systems
; In-situ observations
; Land surface modeling
; Least square estimation
; Reflecting surface
; Surface soil moisture
; Volumetric soil moistures
; Signal to noise ratio
; aboveground biomass
; data set
; GNSS
; ground-based measurement
; growth
; land surface
; least squares method
; observational method
; satellite data
; signal-to-noise ratio
; smoothing
; soil moisture
; wheat
; France
; Triticum aestivum
英文摘要: This work aims to estimate soil moisture and vegetation height from Global Navigation Satellite System (GNSS) Signal to Noise Ratio (SNR) data using direct and reflected signals by the land surface surrounding a ground-based antenna. Observations are collected from a rainfed wheat field in southwestern France. Surface soil moisture is retrieved based on SNR phases estimated by the Least Square Estimation method, assuming the relative antenna height is constant. It is found that vegetation growth breaks up the constant relative antenna height assumption. A vegetation-height retrieval algorithm is proposed using the SNR-dominant period (the peak period in the average power spectrum derived from a wavelet analysis of SNR). Soil moisture and vegetation height are retrieved at different time periods (before and after vegetation's significant growth in March). The retrievals are compared with two independent reference data sets: in situ observations of soil moisture and vegetation height, and numerical simulations of soil moisture, vegetation height and above-ground dry biomass from the ISBA (interactions between soil, biosphere and atmosphere) land surface model. Results show that changes in soil moisture mainly affect the multipath phase of the SNR data (assuming the relative antenna height is constant) with little change in the dominant period of the SNR data, whereas changes in vegetation height are more likely to modulate the SNR-dominant period. Surface volumetric soil moisture can be estimated ( R 2g Combining double low line g 0.74, RMSEg Combining double low line g 0.009g m3g mg '3) when the wheat is smaller than one wavelength (g 1/4 19g cm). The quality of the estimates markedly decreases when the vegetation height increases. This is because the reflected GNSS signal is less affected by the soil. When vegetation replaces soil as the dominant reflecting surface, a wavelet analysis provides an accurate estimation of the wheat crop height ( R 2g Combining double low line g 0.98, RMSEg Combining double low line g 6.2g cm). The latter correlates with modeled above-ground dry biomass of the wheat from stem elongation to ripening. It is found that the vegetation height retrievals are sensitive to changes in plant height of at least one wavelength. A simple smoothing of the retrieved plant height allows an excellent matching to in situ observations, and to modeled above-ground dry biomass. © Author(s) 2017. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/79048
Appears in Collections: 气候变化事实与影响
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作者单位: CNRM, UMR3589 (Météo-France, CNRS), Toulouse, France; Fondation STAE, Toulouse, France; GET, UMR5563, CNRS, Université Paul Sabatier, Toulouse, France; CESBIO, Université de Toulouse, CNES, CNRS, IRD, UPS, Toulouse, France; LEGOS, UMR566 (CNES, CNRS, IRD, UPS), Toulouse, France
Recommended Citation:
Zhang S,, Roussel N,, Boniface K,et al. Use of reflected GNSS SNR data to retrieve either soil moisture or vegetation height from a wheat crop[J]. Hydrology and Earth System Sciences,2017-01-01,21(9)