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 High-Resolution Hurricane Vector Winds from C-Band Dual-Polarization SAR Observations

2014 ◽  
Vol 31 (2) ◽  
pp. 272-286 ◽  
Author(s):  
Biao Zhang ◽  
William Perrie ◽  
Jun A. Zhang ◽  
Eric W. Uhlhorn ◽  
Yijun He
Keyword(s):  
Cost Function ◽  
Surface Wind ◽  
Band Model ◽  
Retrieval Model ◽  
Dual Polarization ◽  
Wind Retrieval ◽  
Wind Speeds ◽  
Geophysical Model ◽  
Consistency Results ◽  
Geophysical Model Function

Abstract This study presents a new approach for retrieving hurricane surface wind vectors utilizing C-band dual-polarization (VV, VH) synthetic aperture radar (SAR) observations. The copolarized geophysical model function [C-band model 5.N (CMOD5.N)] and a new cross-polarized wind speed retrieval model for dual polarization [C-band cross-polarized ocean surface wind retrieval model for dual-polarization SAR (C-2POD)] are employed to construct a cost function. Minimization of the cost function allows optimum estimates for the wind speeds and directions. The wind direction ambiguities are removed using a parametric two-dimensional sea surface inflow angle model. To evaluate the accuracy of the proposed method, two RADARSAT-2 SAR images of Hurricanes Bill and Bertha are analyzed. The retrieved wind speeds and directions are compared with collocated Quick Scatterometer (QuikSCAT) winds, showing good consistency. Results suggest that the proposed method has good potential to retrieve hurricane surface wind vectors from dual-polarization SAR observations.

scholarly journals Validation of NOAA CyGNSS Wind Speed Product with the CCMP Data

2021 ◽  
Vol 13 (9) ◽  
pp. 1832
Author(s):  
Xiaohui Li ◽  
Dongkai Yang ◽  
Jingsong Yang ◽  
Guoqi Han ◽  
Gang Zheng ◽  
...  
Keyword(s):  
Wind Speed ◽  
Comprehensive Evaluation ◽  
Surface Wind ◽  
Temporal Analysis ◽  
Satellite System ◽  
Wind Retrieval ◽  
Sea Surface Wind ◽  
Geophysical Model ◽  
Geophysical Model Function ◽  
Global Navigation Satellite

The National Aeronautics and Space Administration (NASA) Cyclone Global Navigation Satellite System (CyGNSS) mission was launched in December 2016, which can remotely sense sea surface wind with a relatively high spatio-temporal resolution for tracking tropical cyclones. In recent years, with the gradual development of the geophysical model function (GMF) for CyGNSS wind retrieval, different versions of CyGNSS Level 2 products have been released and their performance has gradually improved. This paper presents a comprehensive evaluation of CyGNSS wind product v1.1 produced by the National Oceanic and Atmospheric Administration (NOAA). The Cross-Calibrated Multi-Platform (CCMP) analysis wind (v02.0 and v02.1 near real time) products produced by Remote Sensing Systems (RSS) were used as the reference. Data pairs between the NOAA CyGNSS and RSS CCMP products were processed and evaluated by the bias and standard deviation SD. The CyGNSS dataset covers the period between May 2017 and December 2020. The statistical comparisons show that the bias and SD of CyGNSS relative to CCMP-nonzero collocations when the flag of CCMP winds is nonzero are –0.05 m/s and 1.19 m/s, respectively. The probability density function (PDF) of the CyGNSS winds coincides with that of CCMP-nonzero. Furthermore, the average monthly bias and SD show that CyGNSS wind is consistent and reliable generally. We found that negative deviation mainly appears at high latitudes in both hemispheres. Positive deviation appears in the China Sea, the Arabian Sea, and the west of Africa and South America. Spatial–temporal analysis demonstrates the geographical anomalies in the bias and SD of the CyGNSS winds, confirming that the wind speed bias shows a temporal dependency. The verification and comparison show that the remotely sensed wind speed measurements from NOAA CyGNSS wind product v1.1 are in good agreement with CCMP winds.

scholarly journals Towards the Sea Wind Measurement with the Airborne Scatterometer Having the Rotating-Beam Antenna Mounted over Fuselage

2021 ◽  
Vol 13 (24) ◽  
pp. 5165
Author(s):  
Alexey Nekrasov ◽  
Alena Khachaturian
Keyword(s):  
Remote Sensing ◽  
Surface Wind ◽  
Rotating Beam ◽  
Partial Shading ◽  
Wind Measurement ◽  
Wind Retrieval ◽  
Sea Surface Wind ◽  
Geophysical Model ◽  
Geophysical Model Function ◽  
Sea Wind

Extension of the existing airborne radars’ applicability is a perspective approach to the remote sensing of the environment. Here we investigate the capability of the rotating-beam radar installed over the fuselage for the sea surface wind measurement based on the comparison of the backscatter with the respective geophysical model function (GMF). We also consider the robustness of the proposed approach to the partial shading of the underlying water surface by the aircraft nose, tail, and wings. The wind retrieval algorithms have been developed and evaluated using Monte-Carlo simulations. We find our results promising both for the development of new remote sensing systems as well as the functional enhancement of existing airborne radars.

scholarly journals Aquarius geophysical model function and combined active passive algorithm for ocean surface salinity and wind retrieval

2014 ◽  
Vol 119 (8) ◽  
pp. 5360-5379 ◽  
Author(s):  
Simon Yueh ◽  
Wenqing Tang ◽  
Alexander Fore ◽  
Akiko Hayashi ◽  
Yuhe T. Song ◽  
...  
Keyword(s):  
Ocean Surface ◽  
Model Function ◽  
Surface Salinity ◽  
Wind Retrieval ◽  
Geophysical Model ◽  
Geophysical Model Function

scholarly journals Validation of Backscatter Measurements from the Advanced Scatterometer on MetOp-A

2011 ◽  
Vol 29 (1) ◽  
pp. 77-88 ◽  
Author(s):  
C. Anderson ◽  
J. Figa ◽  
H. Bonekamp ◽  
J. J. W. Wilson ◽  
J. Verspeek ◽  
...  
Keyword(s):  
Incidence Angle ◽  
Absolute Calibration ◽  
Calibration Error ◽  
Wind Fields ◽  
Worst Case ◽  
Antarctic Sea Ice ◽  
Geophysical Model ◽  
Geophysical Model Function ◽  
Calibration Accuracy ◽  
Ocean Wind

Abstract The Advanced Scatterometer (ASCAT) on the Meteorological Operational (MetOp) series of satellites is designed to provide data for the retrieval of ocean wind fields. Three transponders were used to give an absolute calibration and the worst-case calibration error is estimated to be 0.15–0.25 dB. In this paper the calibrated data are validated by comparing the backscatter from a range of naturally distributed targets against models developed from European Remote Sensing Satellite (ERS) scatterometer data. For the Amazon rainforest it is found that the isotropic backscatter decreases from −6.2 to −6.8 dB over the incidence angle range. The ERS value is around −6.5 dB. All ASCAT beams are within 0.1 dB of each other. Rainforest backscatter over a 3-yr period is found to be very stable with annual changes of approximately 0.02 dB. ASCAT ocean backscatter is compared against values from the C-band geophysical model function (CMOD-5) using ECMWF wind fields. A difference of approximately 0.2 dB below 55° incidence is found. Differences of over 1 dB above 55° are likely due to inaccuracies in CMOD-5, which has not been fully validated at large incidence angles. All beams are within 0.1 dB of each other. Backscatter from regions of stable Antarctic sea ice is found to be consistent with model backscatter except at large incidence angles where the model has not been validated. The noise in the ice backscatter indicates that the normalized standard deviation of the backscatter values Kp is around 4.5%, which is consistent with the expected value. These results agree well with the expected calibration accuracy and give confidence that the calibration has been successful and that ASCAT products are of high quality.

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 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.

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
Sign in / Sign up

Export Citation Format

Share Document