scholarly journals Towards the Sea Ice and Wind Measurement by a C-Band Scatterometer at Dual VV/HH Polarization: A Prospective Appraisal

2020 ◽  
Vol 12 (20) ◽  
pp. 3382
Author(s):  
Alexey Nekrasov ◽  
Alena Khachaturian ◽  
Ján Labun ◽  
Pavol Kurdel ◽  
Mikhail Bogachev
Keyword(s):  
Wind Speed ◽  
Sea Ice ◽  
Cross Sections ◽  
Potential Application ◽  
Geophysical Model ◽  
Radar Cross Sections ◽  
Statistical Distance ◽  
Sea Wind ◽  
Ice Water ◽  
Discrimination Method

Following the mission science plan of EPS/Metop-SG C-band scatterometer for 2023–2044, we consider the potential application of the sea ice/water discrimination method based on the minimum statistical distance of the measured normalized radar cross sections (NRCS) to the geophysical model functions (GMF) of the sea ice and water, respectively. The application of the method is considered for the classical spacecraft scatterometer geometry with three fixed fan-beam antennas and the hypothetical prospective scatterometer geometry with the five fixed fan-beam antennas. Joint vertical (VV) and horizontal (HH) transmit and receive polarization are considered for the spaceborne scatterometer geometries. We show explicitly that the hypothetical five fixed fan-beam antenna geometry combined with the dual VV and HH polarization for all antennas provides better estimates of the sea wind speed and direction as well as sea ice/water discrimination during single spacecraft pass. The sea ice/water discrimination algorithms developed for each scatterometer geometry and dual VV/HH polarization are presented. The obtained results can be used to optimize the design of new spaceborne scatterometers and will be beneficial to the forthcoming satellite missions.

scholarly journals On Sea Ice Measurement by a C-Band Scatterometer at VV Polarization: Methodology Optimization Based on Computer Simulations

2019 ◽  
Vol 11 (21) ◽  
pp. 2518 ◽  
Author(s):  
Alexey Nekrasov ◽  
Alena Khachaturian ◽  
Evgeny Abramov ◽  
Oleg Markelov ◽  
Mikhail Bogachev
Keyword(s):  
Sea Ice ◽  
Computer Simulations ◽  
Wind Direction ◽  
Point Of View ◽  
Wind Vector ◽  
Geophysical Model ◽  
Beam Geometry ◽  
Statistical Distance ◽  
Ice Water ◽  
Microwave Backscatter

We consider sea ice and water microwave backscatter features at the C-band with vertical transmit and receive polarization and present a method for sea ice/water discrimination using a multiple fixed fan-beam satellite scatterometer. The method is based on the criterion of the minimum statistical distance of measured backscatter values to the sea ice and water (CMOD7) geophysical model functions. Implementation of the method is considered both for a typical three fan-beam geometry as well as for a potential five fan-beam geometry of a satellite scatterometer. By using computer simulations, we show explicitly that the number of looks at the same cell from different azimuthal directions needs to be increased to provide better (unambiguous) retrieval of the wind vector and sea ice/water discrimination. The algorithms for sea ice/water discrimination are described, and the results obtained are also discussed along with recommendations for the number of different azimuthal looks (beams) at the same cell from the point of view of sea ice/water discrimination as well as unambiguous wind direction retrieval during the satellite’s single pass.

scholarly journals Ocean Wind Retrieval Models for RADARSAT Constellation Mission Compact Polarimetry SAR

2018 ◽  
Vol 10 (12) ◽  
pp. 1938 ◽  
Author(s):  
Tianqi Sun ◽  
Guosheng Zhang ◽  
William Perrie ◽  
Biao Zhang ◽  
Changlong Guan ◽  
...  
Keyword(s):  
Cross Sections ◽  
Quadratic Function ◽  
Retrieval Model ◽  
Retrieval Models ◽  
Wind Retrieval ◽  
Geophysical Model ◽  
Radar Cross Sections ◽  
Geophysical Model Function ◽  
Ocean Wind

We propose two new ocean wind retrieval models for right circular-vertical (RV) and right circular-horizontal (RH) polarizations respectively from the compact-polarimetry (CP) mode of the RADARSAT Constellation Mission (RCM), which is scheduled to be launched in 2019. For compact RV-polarization (right circular transmit and vertical receive), we build the wind retrieval model (denoted CoVe-Pol model) by employing the geophysical model function (GMF) framework and a sensitivity analysis. For compact RH polarization (right circular transmit and horizontal receive), we build the wind retrieval model (denoted the CoHo-Pol model) by using a quadratic function to describe the relationship between wind speed and RH-polarized normalized radar cross-sections (NRCSs) along with radar incidence angles. The parameters of the two retrieval models are derived from a database including wind vectors measured by in situ National Data Buoy Center (NDBC) buoys and simulated RV- and RH-polarized NRCSs and incidence angles. The RV- and RH-polarized NRCSs are generated by a RCM simulator using C-band RADARSAT-2 quad-polarized synthetic aperture radar (SAR) images. Our results show that the two new RCM CP models, CoVe-Pol and CoHo-POL, can provide efficient methodologies for wind retrieval.

scholarly journals Study on Non-Bragg Microwave Backscattering from Sea Surface Covered with and without Oil Film at Moderate Incidence Angles

2021 ◽  
Vol 13 (13) ◽  
pp. 2443
Author(s):  
Honglei Zheng ◽  
Jie Zhang ◽  
Ali Khenchaf ◽  
Xiao-Ming Li
Keyword(s):  
Cross Sections ◽  
Sea Surface ◽  
Scale Model ◽  
Bragg Scattering ◽  
Total Scattering ◽  
Microwave Scattering ◽  
Wind Speeds ◽  
Geophysical Model ◽  
Radar Echoes ◽  
Radar Cross Sections

In the past decades, Bragg scattering has been considered to be an important scattering mechanism of microwave backscattering from sea surfaces. However, as reported in many recent literatures, non-Bragg scattering (which is often attributed to wave breaking) also makes a significant impact on radar scattering, especially for Horizontal–Horizontal (HH) polarized radar signals. To date, we know far less about non-Bragg scattering than Bragg scattering. Herein, this paper carries out an investigation on non-Bragg scattering and its effect on radar echoes at moderate incidence angles, both for oil-free and oil-covered sea surfaces. This paper firstly presents a systematic comparison of several sea spectra commonly used for the simulation of microwave scattering from sea surfaces. It is found that none of them perform well for the description of Bragg waves. Then, the “pure” Bragg wave spectra are inverted in the framework of the two-scale model (TSM) and geophysical model functions (GMFs). The normalized radar cross sections (NRCS) related to total scattering, non-Bragg scattering, and “pure” Bragg scattering in C, X, and Ku-bands are simulated under various conditions (i.e., incidence angles, wind speeds, and wind directions). Quantitative assessments of the relative contributions of non-Bragg scattering to total scattering are conducted. We also perform a survey on the non-Bragg scattering from the oil-covered sea surface. This article provides some new insights for a better understanding of the non-Bragg microwave scattering from rough sea surfaces at moderate incidence angles.

scholarly journals Summer Antarctic sea ice as seen by ASAR and AMSR-E and observed during two IPY field cruises: a case study

2011 ◽  
Vol 52 (57) ◽  
pp. 327-336 ◽  
Author(s):  
Ahmet E. Tekeli ◽  
Stefan Kern ◽  
Stephen F. Ackley ◽  
Burcu Ozsoy-Cicek ◽  
Hongjie Xie
Keyword(s):  
Sea Ice ◽  
Cross Sections ◽  
Ice Core ◽  
First Year ◽  
International Polar Year ◽  
Brightness Temperatures ◽  
Earth Observing System ◽  
Antarctic Sea Ice ◽  
Radar Cross Sections ◽  
International Polar

AbstractEnvisat Advanced Synthetic Aperture Radar (ASAR) Wide Swath Mode (WSM) images are used to derive C-band HH-polarization normalized radar cross sections (NRCS). These are compared with ice-core analysis and visual ship-based observations of snow and ice properties observed according to the Antarctic Sea Ice Processes and Climate (ASPeCt) protocol during two International Polar Year summer cruises (Oden 2008 and Palmer 2009) in West Antarctica. Thick first-year (TFY) and multi-year (MY) ice were the dominant ice types. the NRCS value ranges between –16.3 ± 1.1 and –7.6 ± 1.0 dB for TFY ice, and is –12.6 ± 1.3 dB for MY ice; for TFY ice, NRCS values increase from –~15 dB to –9 dB from December/January to mid-February. In situ and ASPeCt observations are not, however, detailed enough to interpret the observed NRCS change over time. Co-located Advanced Microwave Scanning Radiometer–Earth Observing System (AMSR-E) vertically polarized 37 GHz brightness temperatures (TB37V), 7 day and 1 day averages as well as the TB37V difference between ascending and descending AMSR-E overpasses suggest the low NRCS values (–15 dB) are associated with snowmelt being still in progress, while the change towards higher NRCS values (–9 dB) is caused by commencement of melt– refreeze cycles after about mid-January.

New Method for Internal Wave Parameters Retrieval by SAR

2015 ◽  
Vol 1092-1093 ◽  
pp. 1326-1330
Author(s):  
Kai Guo Fan ◽  
Peng Chen ◽  
Yan Zhen Gu ◽  
Ting Ting Liu ◽  
Wei Wang
Keyword(s):  
Wind Speed ◽  
Internal Wave ◽  
Cross Sections ◽  
Kdv Equation ◽  
Surface Current ◽  
New Method ◽  
Sar Image ◽  
Wave Parameters ◽  
Radar Cross Sections ◽  
The Kdv Equation

This paper introduce a new method for extracting internal wave parameters from SAR image. The surface current induced by the internal wave is simulated according to the KDV equation. Then the radar cross section induced by the internal wave can be calculated. The wind speed and pycnocline depth are modified using the dichotomy method step by step which causes the simulation radar cross sections close to those measured from the SAR image. Finally, both the wind speed and pycnocline depth can be obtained. This method is tested on the example of an SAR image. The simulated internal wave signal is consistent with the radar cross sections of SAR images. Their correlation coefficient is up to 90%, which indicates that this method is convergent and applicable.

Variational estimation of radar cross-sections

1990 ◽  
Vol 137 (4) ◽  
pp. 237 ◽  
Author(s):  
D.A. Edwards ◽  
R.A. McCulloch ◽  
W.T. Shaw
Keyword(s):  
Cross Sections ◽  
Radar Cross Sections

scholarly journals Sea-ice habitat minimizes grazing impact and predation risk for larval Antarctic krill

Polar Biology ◽  
2021 ◽  
Author(s):  
Carmen L. David ◽  
Fokje L. Schaafsma ◽  
Jan A. van Franeker ◽  
Evgeny A. Pakhomov ◽  
Brian P. V. Hunt ◽  
...  
Keyword(s):  
Sea Ice ◽  
Predation Risk ◽  
Water Column ◽  
Antarctic Krill ◽  
Standing Stock ◽  
Euphausia Superba ◽  
Grazing Impact ◽  
Water Interface ◽  
Winter Habitat ◽  
Ice Water

AbstractSurvival of larval Antarctic krill (Euphausia superba) during winter is largely dependent upon the presence of sea ice as it provides an important source of food and shelter. We hypothesized that sea ice provides additional benefits because it hosts fewer competitors and provides reduced predation risk for krill larvae than the water column. To test our hypothesis, zooplankton were sampled in the Weddell-Scotia Confluence Zone at the ice-water interface (0–2 m) and in the water column (0–500 m) during August–October 2013. Grazing by mesozooplankton, expressed as a percentage of the phytoplankton standing stock, was higher in the water column (1.97 ± 1.84%) than at the ice-water interface (0.08 ± 0.09%), due to a high abundance of pelagic copepods. Predation risk by carnivorous macrozooplankton, expressed as a percentage of the mesozooplankton standing stock, was significantly lower at the ice-water interface (0.83 ± 0.57%; main predators amphipods, siphonophores and ctenophores) than in the water column (4.72 ± 5.85%; main predators chaetognaths and medusae). These results emphasize the important role of sea ice as a suitable winter habitat for larval krill with fewer competitors and lower predation risk. These benefits should be taken into account when considering the response of Antarctic krill to projected declines in sea ice. Whether reduced sea-ice algal production may be compensated for by increased water column production remains unclear, but the shelter provided by sea ice would be significantly reduced or disappear, thus increasing the predation risk on krill larvae.

scholarly journals Tank study of physico-chemical controls on gas content and composition during growth of young sea ice

2002 ◽  
Vol 48 (161) ◽  
pp. 177-191 ◽  
Author(s):  
Jean-Louis Tison ◽  
Christian Haas ◽  
Marcia M. Gowing ◽  
Suzanne Sleewaegen ◽  
Alain Bernard
Keyword(s):  
Sea Ice ◽  
Sea Water ◽  
Bubble Nucleation ◽  
Water Dynamics ◽  
Gas Content ◽  
First Year ◽  
Water Interface ◽  
Atmospheric Gases ◽  
Physico Chemical ◽  
Ice Water

AbstractDuring an ice-tank experiment, samples were taken to study the processes of acquisition and alteration of the gas properties in young first-year sea ice during a complete growth–warming–cooling cycle. The goal was to obtain reference levels for total gas content and concentrations of atmospheric gases (O2, N2, CO2) in the absence of significant biological activity. The range of total gas-content values obtained (3.5–18 mL STP kg−1) was similar to previous measurements or estimates. However, major differences occurred between current and quiet basins, showing the role of the water dynamics at the ice–water interface in controlling bubble nucleation processes. Extremely high CO2concentrations were observed in all the experiments (up to 57% in volume parts). It is argued that these could have resulted from two unexpected biases in the experimental settings. Concentrations in bubbles nucleated at the interface are controlled by diffusion both from the ice–water interface towards the well-mixed reservoir and between the interface water and the bubble itself. This double kinetic effect results in a transition of the gas composition in the bubbles from values close to solubility in sea water toward values close to atmospheric, as the ice cover builds up.

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