• Korean Journal of Remote Sensing
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• v.24 no.6
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• pp.559-569
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• 2008

The Geostationary Ocean Color Imager (GOCI) on board the Communication Ocean Meteorological Satellite (COMS), the first geostationary ocean color sensor, requires accurate atmospheric correction since its eight bands are also affected by atmospheric constituents such as gases, molecules and atmospheric aerosols. Unlike gases and molecules in the atmosphere, aerosols can interact with sunlight by complex scattering and absorption properties. For the purpose of qualified ocean remote sensing, understanding of aerosol-radiation interactions is needed. In this study, we show micro-physical and optical properties of aerosols using the Optical Property of Aerosol and Cloud (OPAC) aerosol models. Aerosol optical properties, then, were used to analysis the relationship between theoretical satellite measured radiation from radiative transfer calculations and aerosol optical thickness (AOT) under various environments (aerosol type and loadings). It is found that the choice of aerosol type makes little different in AOT retrieval for AOT<0.2. Otherwise AOT differences between true and retrieved increase as AOT increases. Furthermore, the differences between the AOT and angstrom exponent from standard algorithms and this study, and the comparison with ground based sunphotometer observations are investigated. Over the northeast Asian region, these comparisons suggest that spatially averaged mean AOT retrieved from this study is much better than from standard ocean color algorithm. Finally, these results will be useful for aerosol retrieval or atmospheric correction of COMS/GOCI data processing.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.14 no.1
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• pp.37-41
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• 1978

Optical properties were studied in the costal waters of the southern part of Korea based on twenty oceanographic stations from 1 st to 9 th February, 1977. Submarine daylight intensity was measured by using an underwater luxmeter (Toshiba No.9). Daylight intensity in the upper 30m depth layer was measured at 1 m depth interval. The absorption coefficient of the sea water in the area ranged from 0.101 to 2.539 (mean 0.578). The Secchi-disc depth in the area ranged from 0.8 to 13 meters (mean 5.33 meters). The relationship between absorption coefficient (K) and transparency (D) was k= 1. 704/ D. The mean water color in the area was 5. 75 (3-9) in Forel scales. The rates of light penetration for daylight at 1m layer in the area ranged from 13.18 to 82. 05% and the mean was 59.56%, while the rate at 5m layer ranged from 0.007 to 46.1% and the mean was 18.47%.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.11 no.1
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• pp.8-14
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• 1975

The optical properties of the sea water were studied by use of underwater lux-meters in the coastal waters of Busan from May to November 1975. The absorption coefficient of the sea water in the area ranges from O. 169 to 1. 049 and the mean absorpflOn coefficient is 0.413. Maximum monthly mean absorption coefficient (0. 56) was observed in August, while the minimum was O. 338 in September. There was a distinct discontinuity layer of the absorption coefficient in accordance with the thermocline and the halocline in summer. The mean transparency of the area was 3. 8 meters, and transparency in autumn was higher than that in summer. The relation between absorption coefficient (m) and transparency (D) was deduced, m=1. 57/ D. The rate of light penetration at 5 m-layer of sea water was 2. 5 percent when the solar altitude was six degree in July 1975.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.12 no.1
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• pp.7-12
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• 1976

The optical properties of the sea water were studied by use of underwater photometers in the coastal waters of Busan, from December 1975 to May 1976. The absorption coefficient of the sea water in the area ranged from 0.223 to 0.901 and the mean was 0.355. Maximum valae of monthly mean was 0.454 in December, while the minium was 0.301 in January. The transparency in winter was higher than that in spring and the mean was 4. 7 meters. The relation between absorption coefficient (m) and transparency (D) was m= 1. 67/ D. The rate of light penetration at 5 m-layer in the area ranged from 1. 73 to 24.09 percent and the mean was 13.63 percent, while the rate at 10 m-layer ranged from 0.067 to 8.05 percent and the mean was 2.95 percent.

• Korean Journal of Remote Sensing
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• v.37 no.3
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• pp.615-625
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• 2021

The coastal areas around Palau Island and Tonga Island, near the Pacific equator, consist of coral reefs, mangrove and seaweed. In particular, understanding the optical properties of sea surface water in coral reef habitats helps improve the accuracy of remote sensing based habitat mapping and identify tropical ecosystem characteristics. Here, we collected spectral characteristics of sea surface water of Palau Island and Tonga Island and analyzed the concentration of suspended matters, absorption coefficient, and remote sensing reflectance to understand the seawater characteristics of the coral reef habitats. Based on the results of the suspended matter concentration analysis, we developed and verified an empirical algorithm to derive the concentration from satellite data using remote sensing reflectance of three bands, 555, 625, 660 nm, showed a high determinant coefficient, 0.98. In conclusion, coral reef habitats in tropical regions are characterized by CASE-I water in terms of the marine optics with oligotrophic properties, and require monitoring using continuous collection and analysis of field data.

• Korean Journal of Remote Sensing
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• v.37 no.5_1
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• pp.1125-1133
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• 2021

This study attempted to understand seawater characteristics like chlorophyll concentration (CHL), total suspended matter concentration (TSM), absorption characteristics, and remote sensing reflectance around Weno Island, Micronesia, located in the South Pacific Ocean near the equator. 50 in-situ measurement from May to June 2013 were analyzed and compared with data from around Korean peninsula. CHL around Weno Island was 0.11-0.49 mg/m³ (average 0.26 mg/m³), and TSM was 0.03-0.31 g/m³, (average 0.16 g/m³), showing typical clear water characteristics. Absorption coefficient of total suspended matters at 443 nm showed over 0.5 times less than that from East Sea and the slope of absorption coefficient spectrum of dissolved organic matter showed much larger than that of Korean peninsula, indicating the concentration of organic matter is very low and dissolved organic matter of marine origin is considered to be the main component in the study area. As a result of comparing the remote sensing reflectance spectrum with that of coastal waters around the Korean peninsula, coastal waters around Weno Island showed typical CASE-1 water properties. It was possible to understand the marine optical characteristics of coral reef habitats in tropical waters, and it can be used to develop seawater algorithms specialized in the study area.

• Korean Journal of Remote Sensing
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• v.16 no.4
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• pp.315-325
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• 2000

Observations were made to validate ocean color algorithms in the Ulleung Basin, East Sea in May 2000. Small scale and meso-scale surveys were conducted for the validation of ocean color products (nLw: normalized water-leaving radiance and chlorophyll concentration). There were discrepancies between SeaWiFS and in situ nLw showing the current aerosol models of standard SeaWiFS processing software are less than adequate (Gordon and Wang, 1994). Applying the standard SeaWiFS in-water algorithm resulted in an overestimation of chlorophyll concentration. This is because that CDOM absorption was higher than the estimated chlorophyll absorption. TSS concentration was also high. Therefore, the study region deviated from Case 1 waters. The source of these materials seems to be the entrainment of coastal water by the Tsushima Warm Current. Study of the bio-optical properties in other season is desirable.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.36 no.4
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• pp.205-211
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• 2018

Remote estimation of water quality via radiometric instruments provides a convenient means for monitoring environmental changes in water bodies in wide areas. Combined with platforms such as satellite, manned/unmanned vehicles, it reduces the measurement cost and time for acquiring water quality information on the interested target areas. To develop accurate retrieval algorithms, however, acquisition of in-situ measurements from various optical environment is critical. In this study, hyperspectral radiometric measurements, the coincident water quality variables, and its optical properties were obtained to analyze the optical environment of the study area. Field data collected around the Tongyeong area showed that the area has optically complex environment, with occasional outbreak of red tide in summer seasons. Effect of water constituents on the optical variables (remote sensing reflectance and absorption coefficients) were qualitatively analyzed.

• Journal of the Korean earth science society
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• v.43 no.5
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• pp.591-603
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• 2022

The color and optical properties of seawater are determined by the interaction between dissolved organic and inorganic substances and plankton contained in it. The Ieodo - Ocean Research Institute (I-ORS), located in the East China Sea, is affected by the low salinity of the Yangtze River in the west and the Tsushima Warm Current in the south. Thus, it is a suitable site for analyzing the fluctuations in circulation and optical properties around the Korean Peninsula. In this study, seawater surrounding the I-ORS was classified according to its optical characteristics using the satellite remote reflectance observed with Moderate Resolution Imaging Spectroradiometer (MODIS)/Aqua and National Aeronautics and Space Administration (NASA) bio-Optical Marine Algorithm Dataset (NOMAD) from January 2016 to December 2020. Additionally, the variation characteristics of optical water types (OWTs) from different seasons were presented. A total of 59,532 satellite match-up data (d ≤ 10 km) collected from seawater surrounding the I-ORS were classified into 23 types using the spectral angle mapper. The OWTs appearing in relatively clear waters surrounding the I-ORS were observed to be greater than 50% of the total. The maximum OWTs frequency in summer and winter was opposite according to season. In particular, the OWTs corresponding to optically clear seawater were primarily present in the summer. However, the same OWTs were lower than overall 1% rate in winter. Considering the OWTs fluctuations in the East China Sea, the I-ORS is inferred to be located in the transition zone of seawater. This study contributes in understanding the optical characteristics of seawater and improving the accuracy of satellite ocean color variables.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.3
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• pp.196-200
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• 2019

In this study, photoluminescence (PL) analysis was performed to evaluate the optical properties of commercial ZnO substrates. Particular attention was paid to the bound exciton (BX) luminescence, which is usually the strongest emission intensity of commercial substrates. At 15 K, PL analysis revealed that the BX peak due to donor-type impurities (donor-bound-exciton; DX) dominated, while two-electron satellite (TES) emission, donor-accepter pair (DAP) emission, and LO-phonon replica emission were also observed. The impurity concentration of the ZnO substrate was determined to be $10^{15}$ to $10^{16}/cm^3$ by examination of the temperature variation of DAP, while the half width and intensity change of the luminescence revealed that the temperature change of BX can be interpreted almost the same as the analysis of free-exciton emission.