scholarly journals The influence of surface canopy water on the relationship between L-band backscatter and biophysical variables in agricultural monitoring

2022 ◽  
Vol 268 ◽  
pp. 112789
Author(s):  
S. Khabbazan ◽  
S.C. Steele-Dunne ◽  
P. Vermunt ◽  
J. Judge ◽  
M. Vreugdenhil ◽  
...  
Keyword(s):  
L Band ◽  
The Relationship ◽  
Canopy Water

scholarly journals POLARIMETRIC CALIBRATION OF L-BAND AIRBORNE SAR DATA

2020 ◽  
Vol V-1-2020 ◽  
pp. 369-374
Author(s):  
A. Maiti ◽  
S. Kumar ◽  
V. Tolpekin ◽  
S. Agarwal
Keyword(s):  
Accurate Estimation ◽  
Distortion Model ◽  
Propagation Of Uncertainty ◽  
Statistical Measures ◽  
Dry Lake ◽  
L Band ◽  
Airborne Sar ◽  
Optimal Kernel ◽  
Target Characteristics ◽  
The Relationship

Abstract. The PolSAR calibration ensures that the relationship between the SAR observations and the target characteristics on the ground are consistent and resembles the theoretical estimation which in turn improves the overall data quality. Essentially, calibration prevents the propagation of uncertainty into further analysis to characterise the target. In this study, the UAVSAR L-Band data of Rosamond dry lake bed has been calibrated. The calibration of amplitude and phase are carried out with the help of the corner reflector array present in the Rosamond site. The dataset is further calibrated for the crosstalk and channel imbalance using the Quegan’s distortion model. Since the crosstalk distortion model requires an accurate estimation of the covariance matrix, the optimal kernel size for the its computation is selected based on the distortion model behaviour with varying window sizes. Furthermore, the effectiveness of the calibration process has been studied using polarimetric signatures and other statistical measures.

Inferring the effects of surface canopy water on VOD estimation from L-band backscatter 

2021 ◽  
Author(s):  
Saeed Khabbazan ◽  
Paul.C. Vermunt ◽  
Susan.C. Steele Dunne ◽  
Ge Gao ◽  
Mariette Vreugdenhil ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Linear Relationship ◽  
Water Content ◽  
Growing Season ◽  
Empirical Parameter ◽  
Vegetation Water Content ◽  
L Band ◽  
Vegetation Water ◽  
Canopy Water ◽  
Effect Of Surface

<p>Quantification of vegetation parameters such as Vegetation Optical Depth (VOD) and Vegetation Water Content (VWC) can be used for better irrigation management, yield forecasting, and soil moisture estimation. Since VOD is directly related to vegetation water content and canopy structure, it can be used as an indicator for VWC. Over the past few decades, optical and passive microwave satellite data have mostly been used to monitor VWC. However, recent research is using active data to monitor VOD and VWC benefitting from their high spatial and temporal resolution.</p><p>Attenuation of the microwave signal through the vegetation layer is parametrized by the VOD. VOD is assumed to be linearly related to VWC with the proportionality constant being an empirical parameter b. For a given wavelength and polarization, b is assumed static and only parametrized as a function of vegetation type. The hypothesis of this study is that the VOD is not similar for dry and wet vegetation and the static linear relationship between attenuation and vegetation water content is a simplification of reality.</p><p>The aim of this research is to understand the effect of surface canopy water on VOD estimation and the relationship between VOD and vegetation water content during the growing season of a corn canopy. In addition to studying the dependence of VOD on bulk VWC for dry and wet vegetation, the effect of different factors, such as different growth stages and internal vegetation water content is investigated using time series analysis.</p><p>A field experiment was conducted in Florida, USA, for a full growing season of sweet corn. The corn field was scanned every 30 minutes with a truck-mounted, fully polarimetric, L-band radar. Pre-dawn vegetation water content was measured using destructive sampling three times a week for a full growing season. VWC could therefore be analyzed by constituent (leaf, stem, ear) or by height. Meteorological data, surface canopy water (dew or interception), and soil moisture were measured every 15 minutes for the entire growing season.</p><p>The methodology of Vreugdenhil et al.  [1], developed by TU Wien for ASCAT data, was adapted to present a new technique to estimate VOD from single-incidence angle backscatter data in each polarization. The results showed that the effect of surface canopy water on the VOD estimation increased by vegetation biomass accumulation and the effect was higher in the VOD estimated from the co-pol compared with the VOD estimated from the cross-pol. Moreover, the surface canopy water considerably affected the regression coefficient values (b-factor) of the linear relationship between VOD and VWC from dry and wet vegetation. This finding suggests that considering a similar b-factor for the dry and the wet vegetation will introduce errors in soil moisture retrievals. Furthermore, it highlights the importance of considering canopy wetness conditions when using tau-omega.</p><ul><li>[1] Vreugdenhil,W. A. Dorigo,W.Wagner, R. A. De Jeu, S. Hahn, andM. J. VanMarle, “Analyzing the vegetation parameterization in the TU-Wien ASCAT soil moisture retrieval,” IEEE Transactions on Geoscience and Remote Sensing, vol. 54, pp. 3513–3531, 2016</li> </ul>

Genotypic Variation in Carbon Isotope Discrimination and Transpiration Efficiency in Wheat. Leaf Gas Exchange and Whole Plant Studies

1990 ◽  
Vol 17 (1) ◽  
pp. 9 ◽  
Author(s):  
AG Condon ◽  
GD Farquhar ◽  
RA Richards
Keyword(s):  
Boundary Layer ◽  
Water Loss ◽  
Dry Matter ◽  
Carbon Isotope Discrimination ◽  
Genotypic Variation ◽  
Transpiration Efficiency ◽  
Layer Resistance ◽  
Boundary Layer Resistance ◽  
The Relationship ◽  
Canopy Water

The relationship between carbon isotope discrimination, Δ, measured in plant dry matter and the ratio of intercellular to atmospheric partial pressures of CO2, pi/pa, in leaves was examined in two glasshouse experiments using 14 wheat genotypes selected on the basis of variation in Δ of dry matter. Genotypic variation in Δ was similar in both experiments, with an average range of 1.8 x 10-3. Variation in pi/pa was significant but the range in pi/pa was relatively small, averaging 0.075. In both experiments, Δ measured in dry matter and pi/pa measured in flag leaves were positively correlated. Variation among genotypes in pi/pa was attributed, approximately equally, to variation in leaf conductance and in photosynthetic capacity. The relationship between plant transpiration efficiency, W* (the amount of above-ground dry matter produced per unit water transpired) and � was also examined. There was a negative correlation between W * and Δ; under well watered conditions and under gradually increasing terminal water stress. The relationship between W* of stressed plants and Δ measured in well watered plants was also negative. These results indicate that genotypic variation in Δ measured in dry matter should provide a reasonable measure of genotypic variation in long-term mean leaf pi/pa in wheat. Further, selection for improved plant transpiration efficiency in wheat under both well watered and terminally water- stressed conditions should be possible based on Δ measured in well watered plants. The extent to which such selection will be effective in improving transpiration efficiency at the field canopy level may depend on the influence of boundary layer resistance on transpirationsal water loss. Under well watered conditions and at full canopy closure, the influence of boundary layer resistance on canopy water loss may be relatively large and stomatal control of water loss may be limited. Under water stress, stomatal control of canopy water loss will be greater.

On the relationship between the circumference of rubber trees and L-band waves

2019 ◽  
Vol 40 (16) ◽  
pp. 6395-6417
Author(s):  
Bambang H. Trisasongko ◽  
David J. Paull ◽  
Amy L. Griffin ◽  
Xiuping Jia ◽  
Dyah R. Panuju
Keyword(s):  
L Band ◽  
The Relationship

Design of Miniaturization Microstrip Filter in L-Band

2013 ◽  
Vol 816-817 ◽  
pp. 1037-1040
Author(s):  
Hao Ru Wang ◽  
Kai Yang ◽  
Xiang Rang Ren ◽  
Yi Meng Liu
Keyword(s):  
Design Theory ◽  
Bandpass Filter ◽  
Filter Design ◽  
Coupling Coefficients ◽  
Microstrip Resonator ◽  
Relative Bandwidth ◽  
L Band ◽  
Capacitive Loading ◽  
Fifth Order ◽  
The Relationship

A curve of the relationship between the gaps of microstrip resonator and coupling coefficients is presented in this paper, which based on the study of small planar microstrip bandpass filter design theory and implementation. According to the curve, a small microstrip bandpass filter with 6.67% relative bandwidth in L-band is designed by Multi-zigzag line and capacitive loading technology. Compared to the similar hairpin line filters, the area of the filter designed in this paper is reduced by 64% with advantage of smaller size and more simple structure. The examples and results of a fifth-order Chebyshev responsible L-band bandpass filter are presented in the end of this paper.

Reconstructing daily cycles of canopy water for the validation of (subdaily) microwave estimates

2021 ◽  
Author(s):  
Paul Vermunt ◽  
Susan Steele-Dunne ◽  
Saeed Khabbazan ◽  
Nick van de Giesen ◽  
Jasmeet Judge
Keyword(s):  
Remote Sensing ◽  
Microwave Remote Sensing ◽  
Water Dynamics ◽  
Fuel Load ◽  
Data Sets ◽  
Destructive Sampling ◽  
Essential Information ◽  
L Band ◽  
Vegetation Water ◽  
Canopy Water

<p>Monitoring rapid, subdaily vegetation water dynamics is key to address fundamental questions surrounding the role of vegetation in the water, carbon and energy cycles, and to provide essential information for detecting and monitoring droughts on local to global scales. Active and passive microwave remote sensing has been used to estimate vegetation water content (VWC), e.g. using vegetation optical depth (VOD), because of the sensitivity of microwave observables to plant dielectric properties. These estimates were used for applications such as fuel load estimation, soil moisture retrieval, crop monitoring and studies on drought propagation. The expected availability of subdaily observations from the next generation of satellites opens the opportunity to also monitor rapid vegetation water dynamics. However, one of the main challenges is the validation of subdaily microwave products.</p><p>VWC is commonly measured through destructive sampling, which is labor- and time-intensive, in particular when this has to be done multiple times per day. Here, we present a proof of concept for a more efficient validation method, using continuously measuring sensors. First, we present our latest study on reconstructing continuous records of VWC in corn, using hydrometeorological data and sparse destructive sampling [Vermunt et al., in prep.]. Second, we present the estimation of surface canopy water (dew, rainfall interception), and illustrate the value of both data sets by using them to analyse our tower-based observations of subdaily fully polarimetric L-band backscatter [1]. The results demonstrate the potential for radar to monitor rapid vegetation water dynamics.</p><p>[1] Vermunt, P. C., Khabbazan, S., Steele-Dunne, S. C., Judge, J., Monsivais-Huertero, A., Guerriero, L., & Liu, P. W. (2020). Response of Subdaily L-Band Backscatter to Internal and Surface Canopy Water Dynamics. IEEE Transactions on Geoscience and Remote Sensing.</p>

Response of Subdaily L-Band Backscatter to Internal and Surface Canopy Water Dynamics

2020 ◽  
pp. 1-16
Author(s):  
Paul C. Vermunt ◽  
Saeed Khabbazan ◽  
Susan C. Steele-Dunne ◽  
Jasmeet Judge ◽  
Alejandro Monsivais-Huertero ◽  
...  
Keyword(s):  
Water Dynamics ◽  
L Band ◽  
Canopy Water

Interstellar gas in the central region of the Galaxy

1967 ◽  
Vol 31 ◽  
pp. 239-251 ◽  
Author(s):  
F. J. Kerr
Keyword(s):  
Central Region ◽  
Galactic Plane ◽  
Neutral Hydrogen ◽  
Continuum Emission ◽  
Galactic Centre ◽  
Interstellar Gas ◽  
Hydrogen Recombination ◽  
The Galaxy ◽  
Centre Region ◽  
The Relationship

A review is given of information on the galactic-centre region obtained from recent observations of the 21-cm line from neutral hydrogen, the 18-cm group of OH lines, a hydrogen recombination line at 6 cm wavelength, and the continuum emission from ionized hydrogen.Both inward and outward motions are important in this region, in addition to rotation. Several types of observation indicate the presence of material in features inclined to the galactic plane. The relationship between the H and OH concentrations is not yet clear, but a rough picture of the central region can be proposed.

The relationship of the scleractinian corals to the rugose corals

Paleobiology ◽  
1980 ◽  
Vol 6 (02) ◽  
pp. 146-160 ◽  
Author(s):  
William A. Oliver
Keyword(s):  
Critical Points ◽  
Scleractinian Corals ◽  
Convincing Evidence ◽  
Early Triassic ◽  
Rugose Corals ◽  
History Of ◽  
The Subject ◽  
Relationship Of ◽  
The Relationship ◽  
Biologic Factors

The Mesozoic-Cenozoic coral Order Scleractinia has been suggested to have originated or evolved (1) by direct descent from the Paleozoic Order Rugosa or (2) by the development of a skeleton in members of one of the anemone groups that probably have existed throughout Phanerozoic time. In spite of much work on the subject, advocates of the direct descent hypothesis have failed to find convincing evidence of this relationship. Critical points are:(1) Rugosan septal insertion is serial; Scleractinian insertion is cyclic; no intermediate stages have been demonstrated. Apparent intermediates are Scleractinia having bilateral cyclic insertion or teratological Rugosa.(2) There is convincing evidence that the skeletons of many Rugosa were calcitic and none are known to be or to have been aragonitic. In contrast, the skeletons of all living Scleractinia are aragonitic and there is evidence that fossil Scleractinia were aragonitic also. The mineralogic difference is almost certainly due to intrinsic biologic factors.(3) No early Triassic corals of either group are known. This fact is not compelling (by itself) but is important in connection with points 1 and 2, because, given direct descent, both changes took place during this only stage in the history of the two groups in which there are no known corals.

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