• Korean Journal of Remote Sensing
• /
• v.29 no.1
• /
• pp.35-43
• /
• 2013

We analyzed the relationships between backscattering coefficients of wheat measured by COSMO-SkyMed SAR and biophysical measurements such as biomass, vegetation water content, and soil moisture over an entire wheat growth period. Backscattering coefficients increased until DOY 129 and then decreased along with fresh weight, dry weight, and vegetation water content. Correlation analysis between backscattering and wheat growth parameters revealed that backscatter correlated well with fresh weight (r=0.88), vegetation water content (r=0.87), and dry weight (r=0.80), while backscatter did not correlated with soil moisture (r=0.18). Prediction equations for estimation of wheat growth parameters from the backscattering coefficients were developed.

• Korean Journal of Remote Sensing
• /
• v.34 no.6_3
• /
• pp.1383-1398
• /
• 2018

Sea surface wind is one of the most fundamental variables for understanding diverse marine phenomena. Although scatterometers have produced global wind field data since the early 1990's, the data has been used limitedly in oceanic applications due to it slow spatial resolution, especially at coastal regions. Synthetic Aperture Radar (SAR) is capable to produce high resolution wind field data. KOMPSAT-5 is the first Korean satellite equipped with X-band SAR instrument and is able to retrieve the sea surface wind. This study presents the validation results of sea surface wind derived from the KOMPSAT-5 backscattering coefficient data for the first time. We collected 18 KOMPSAT-5 ES mode data to produce a matchup database collocated with buoy stations. In order to calculate the accurate wind speed, we preprocessed the SAR data, including land masking, speckle noise reduction, and ship detection, and converted the in-situ wind to 10-m neutral wind as reference wind data using Liu-Katsaros-Businger (LKB) model. The sea surface winds based on XMOD2 show root-mean-square errors of about $2.41-2.74m\;s^{-1}$ depending on backscattering coefficient conversion equations. In-depth analyses on the wind speed errors derived from KOMPSAT-5 backscattering coefficient data reveal the existence of diverse potential error factors such as image quality related to range ambiguity, discrete and discontinuous distribution of incidence angle, change in marine atmospheric environment, impacts on atmospheric gravity waves, ocean wave spectrum, and internal wave.

• Journal of Korea Water Resources Association
• /
• v.56 no.3
• /
• pp.211-224
• /
• 2023

In this study, a soil moisture estimation was performed using the Water Cloud Model (WCM), a backscatter model that considers vegetation based on SAR (Synthetic Aperture Radar). Sentinel-1 SAR and Sentinel-2 MSI (Multi-Spectral Instrument) images of a 40 × 50 km² area including the Yongdam Dam watershed of the Geum River were collected for this study. As vegetation descriptor of WCM, Sentinel-1 based vegetation index RVI (Radar Vegetation Index), depolarization ratio (DR), and Sentinel-2 based NDVI (Normalized Difference Vegetation Index) were used, respectively. Forward modeling of WCM was performed by 3 groups, which were divided by the characteristics between backscattering coefficient and soil moisture. The clearer the linear relationship between soil moisture and the backscattering coefficient, the higher the simulation performance. To estimate the soil moisture, the simulated backscattering coefficient was inverted. The simulation performance was proportional to the forward modeling result. The WCM simulation error showed an increasing pattern from about -12dB based on the observed backscattering coefficient.

• The Magazine of the IEIE
• /
• v.28 no.10
• /
• pp.102.2-103
• /
• 2001

• Korean Journal of Remote Sensing
• /
• v.34 no.2_1
• /
• pp.237-248
• /
• 2018

The vertical distribution of hydrometeor before precipitation near the cloud base has been analyzed using a scanning lidar, rawinsonde data, and Cloud-Resolving Storm Simulator (CReSS). This study mostly focuses on 13 Desember 2016 only. The typical synoptic pattern of lake-effect snowstorm induced easterly in the Yeongdong region. Clouds generated due to high temperature difference between 850 hPa and sea surface (SST) penentrated in the Yeongdong region along with northerly and northeasterly, which eventually resulted precipitation. The cloud base height before the precipitation changed from 750 m to 1,280 m, which was in agreement with that from ceilometer at Sokcho. However, ceilometer tended to detect the cloud base 50 m ~ 100 m below strong signal of lidar backscattering coefficient. As a result, the depolarization ratio increased vertically while the backscattering coefficient decreased about 1,010 m~1,200 m above the ground. Lidar signal might be interpreted to be attenuated with the penetration depth of the cloud layer with of nonspherical hydrometeor (snow, ice cloud). An increase in backscattering signal and a decrease in depolarization ratio occured in the layer of 800 to 1,010 m, probably being associated with an increase in non-spherical particles. There seemed to be a shallow liquid layer with a low depolarization ratio (<0.1) in the layer of 850~900 m. As the altitude increases in the 680 m~850 m, the backscattering coefficient and depolarization ratio increase at the same time. In this range of height, the maximum value (0.6) is displayed. Such a result can be inferred that the nonspherical hydrometeor are distributed by a low density. At this time, the depolarization ratio and the backscattering coefficient did not increase under observed melting layer of 680 m. The lidar has a disadvantage that it is difficult for its beam to penetrate deep into clouds due to attenuation problem. However it is promising to distinguish hydrometeor morphology by utilizing the depolarization ratio and the backscattering coefficient, since its vertical high resolution (2.5 m) enable us to analyze detailed cloud microphysics. It would contribute to understanding cloud microphysics of cold clouds and snowfall when remote sensings including lidar, radar, and in-situ measurements could be timely utilized altogether.

• The Journal of the Acoustical Society of Korea
• /
• v.15 no.2E
• /
• pp.45-49
• /
• 1996

From the reverberation signals received in the shallower water, the surface scattered signals are identified by using the multipath eigneray model that provides launch angles, grazing angles and transmission loss from the high frequency directional source to and from the rough surface. For small scale surface waves, the perturbation method is used to compute the backscattering strength for various grazing angles and wind speeds. A scheme to inversely estimate the wind speed, by which the observed surface reverberation levels are produced, has been tested. In result, for low grazing angles the perturbation method can be used to predict the backscattering stregth, thereby the surface wind can be indirectly estimated.

• Journal of Biomedical Engineering Research
• /
• v.2 no.1
• /
• pp.15-20
• /
• 1981

In this study, the scattering of ultrasound by blood is theoretically studied. At first, the Chernow equation which represents acoustic propagation inside the region of inhomogenieties is modified to be fitted for blood. Then, scattering amplitude and scattering Cross-section at the far-field region are obtained from this equation. In this case, hemotocrit is assumed to be less than 26 per cent, and the red blood cell is modeled as independent scatterer. This study also develops a practical approximation for the backscattering of periodic sinewave bursts by a volume of randomly distributed scatterers, i.e., whole red blood cells. This expression for the received backscattering ultrasound pressure after the n-th burst of narrowband transducer is obtained from an ideal continuous wave transducer's response.

• Proceedings of the KSRS Conference
• /
• 2004.10a
• /
• pp.405-409
• /
• 2004

We chose the Kushiro wetland in Hokkaido, Japan, as a test site to monitor wetland areas. Synthetic aperture radar (SAR) can carry out continuous observation in any weather conditions, and can therefore be used to observe high humidity areas such as wetlands. We applied multi-parameter SAR data (dual-frequency, multi-polarization, and multi-incidence angle) to monitoring the wetland forest. To find the optimum incidence angle and polarization for monitoring the wetland biomass, a simple backscattering model of wetland vegetation was developed and applied to estimate backscattering coefficients for different biomass and surface conditions.

• Proceedings of the KSRS Conference
• /
• v.1
• /
• pp.479-482
• /
• 2006

The absorption coefficient and backscattering properties of phytoplankton were calculated from the Mie theory. Given a simple case that phytoplankton and mineral particles are the only constitutions in seawater, the reflectance $b_b({\lambda})/[a({\lambda})+b_b({\lambda})]$was analyzed. Then the chlorophyll concentrations were estimated from remote sensing OC2 algorithm. The results show that reflectance in short wavelength region is more sensitive to the Chl variation; High mineral concentrations in seawater have significant influence on the reflectance spectrum; the existence of high mineral concentration may result in the mistake in chlorophyll estimation from OC2 algorithm.

• Solar Energy
• /
• v.10 no.1
• /
• pp.57-62
• /
• 1990

The influence of substrate materials on the thermal stability of black chrome coating was investigated by Rutherford backscattering spectrometry(RBS). In order to study thermal degradation the sample were annealed in air for 24 hour at temperature of 450. Cu, Ni, and S.S(Stainless steel 304) were used as substrate for selective coating. The experimental results of substrate diffusion was discussed. It was found that little diffusion of substrate material occurred for the sample pre. pared on stainless steel.