• Proceedings of the KSRS Conference
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• 1999.11a
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• pp.89-94
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• 1999

The paper first proposes an empirical algorithm for detecting dust-loaded airmass observed by Sea Wide Field-of-view Scanner (SeaWiFS). The proposed dust index formula is based on the curvature of the spectral reflectance estimated from the SeaWiFS band 4 (510 nm band) through band 8 (865 nm band) data, assuming "clear ocean water" reflectance. Evaluation of the algorithm is made over several typical Asian dust images including the ones over the Pacific in April, 1998, when a major dust event was reported. The study analyzes the performance and the characteristics of the algorithm by comparing the satellite-derived dust index images with contemporaneous columnar concentration of dust particles predicted by a numerical dust transport model. The comparison reveals several small-scale differences although their dust distribution patterns show good agreement generally.

• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.367-372
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• 2002

Asian dust aerosol layer of 4-6 km altitude accompanied by low clouds was observed by LIDAR and sky-radiometer in Tokyo urban area on April 10, 2001. To synthesize the top of atmosphere (TOA) reflectance, radiative transfer simulation conducted assuming aerosol/cloud vertical structure and aerosol size distribution that were modeled after the ground observations. The refractive index of Asian dust is derived from a laboratory measurement of sampled Chinese soil particles. The synthesized TOA reflectance is compared to the SeaWiFS-derived one sampled at the low cloud pixels whose airmass is the same as the one passed at the observation site. While the two TOA reflectances compare generally well with few percent difference in reflectance, possible sources of the discrepancy are discussed.

• Proceedings of the KSRS Conference
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• v.2
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• pp.913-916
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• 2006

Spatial distribution, seasonal and interannual variability of chlorophyll a concentration in Okhotsk Sea from SeaWiFS data between 2001 and 2004 were describe. An Empirical Orthogonal Function method was applied for analysis data. The ten modes described about 85% of total variance. Two maxima were defined - more intensive in spring and weaker in autumn. The first mode showed zones with chlorophyll a concentration during maximum bloom. The second mode specified timing of spring bloom in various regions in Okhotsk Sea. Analysis of SeaWiFS data indicated connection between highest chlorophyll a concentration and sea surface temperature limits during spring bloom. Similar relation was not found during fall bloom.

• Proceedings of the KSRS Conference
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• v.1
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• pp.316-319
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• 2006

Monthly-mean aerosol parameters derived from the 1998-2004 SeaWiFS observations over East Asian waters are analyzed. SeaWiFS GAC Level 1 data covering the Northeast Asian area are collected and processed by the standard atmospheric correction algorithm released by the SeaWiFS Project to produce daily aerosol optical thickness (AOT) and ${{\AA}}ngstr{\ddot{o}}m$ exponent imageries. Monthly mean AOT and ${{\AA}}ngstr{\ddot{o}}m$ exponent values are extracted from the daily composite images for six study areas chosen from the surrounding waters of Japan. A slight increasing trend of ${{\AA}}ngstr{\ddot{o}}m$ exponent is found and interpreted as about 4-5% increase in submicron fraction of aerosol optical thickness at 550nm. Two cloud screening methods, including the standard cloud masking method of SeaWiFS and the one based on the local variance method, are applied to the SeaWiFS data processing, in an attempt to inspect the influence to the observed statistical uptrend which probably induced by different cloud mask algorithms. The variability comes from the different cloud masking algorithms are discussed.

• Proceedings of the KSRS Conference
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• 2008.10a
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• pp.336-339
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• 2008

Monthly mean data of Angstrom exponent and Aerosol optical thickness (AOT) from Sea-viewing Wide Field-of-view Sensor (SeaWiFS) measurements over the East Asian waters were analyzed. Increasing trend of the satellite-derived Angstrom exponent was found over 1998-2006 while AOT mean was observed stable during the same period. Statistical test showed that annual increase in Angstrom exponent of about 0.01 is statistically significant over three study sub-areas out of six surrounding waters of Japan. Comparison with Aqua/MODIS-derived Angstrom exponent time series over June 2002 through June 2008 showed consistent correlation, with similar statistical significance. The trend of Angstrom exponent was interpreted as increase in fraction of small aerosol particles to give quantitative estimates on the variability of aerosols. The mean increase is evaluated to be about +0.35%/yr or more in terms of the contribution of small particles to the total AOT, or sub-micron fraction (SMF).

• Proceedings of the KSRS Conference
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• 2007.10a
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• pp.57-60
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• 2007

Monthly mean data of ${\AA}ngstr{\ddot{o}}m$ exponent and Aerosol optical thickness (AOT) from Sea-viewing Wide Field-of-view Sensor (SeaWiFS) measurements over the East Asian waters were analyzed. Increasing trend of the satellite-derived ${\AA}ngstr{\ddot{o}}m$ exponent from 1998 to 2004 was found while AOT mean was observed stable during the same period. The trend of ${\AA}ngstr{\ddot{o}}m$ exponent is then interpreted as increase in fraction of small aerosol particles to give quantitative estimates on the variability of aerosols. The mean increase is evaluated to be $4{\sim}5%$ over the 7-year period in terms of the contribution of small particles to the total AOT, or sub-micron fraction (SMF). Possibilities of the observed trend arising from the sensor calibration or algorithm performance are carefully checked, which confirm our belief that this observed trend is rather a real fact than an artifact due to data processing. Another time series of SMF data (2000-2005) estimated from the fine-mode fraction (FMF) of Moderate Resolution Imaging Spectroradiometer (MODIS) supports this observation yet with different calibration system and retrieval algorithms.

• Journal of the Korean Association of Geographic Information Studies
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• v.2 no.2
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• pp.59-68
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• 1999

The study for detecting suspended sediment distribution in Lake Sihwa, which has a large surface area and coastal area, using remote sensing technique was carried out with development of satellite data collected since 1970. The research, however, analysis of spatial distribution and quantity, is not common in domestic study and useful algorithms have not been proposed. In this study, a suspended sediment algorithm was composed with in-situ data obtained in study area and remote sensing reflectance obtained in-water optical instrument, which has SeaWiFS wavelength bands. However, when the algorithm was applied to Landsat TM data, including an in-situ data set, and some problems arose. The composition of the algorithm which was structured with band difference and band ratio showed the correlation of $R^2$=0.7649 with concentration of suspended sediments. And, between calculated and observed concentration of suspended sediments there was a correlation of $R^2$=0.6959. However, remote sensing reflectance obtained from Landsat TM is not good for the estimation of concentration of suspended sediments, because of high concentration of chlorophyll and CDOM(colored dissolved organic matter).