• Atmosphere
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• v.15 no.4
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• pp.203-211
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• 2005

One algorithm has been developed for retrieving aerosol optical thickness from GMS-5 visible channel measurements, and then the algorithm was applied for obtaining the geographical distribution of aerosol optical thickness over East Asia during April 2002. Algorithm employs a look-up table based upon radiative transfer calculations with solar geometry, aerosol optical thickness, and surface albedo as inputs. Validation was conducted by comparing retrieved aerosol optical thickness with measured values from ground-based sky radiation measurements at Anmyon Do, Korea. It was found that the correlation coefficient is 0.71 with -0.03 of bias and 0.34 of root mean square error, suggesting that the algorithm developed in this study can be used for estimating aerosol optical thickness in a quantitative sense.

• Journal of Korean Society for Atmospheric Environment
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• v.15 no.6
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• pp.739-746
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• 1999

The spectral aerosol optical thickness of vertical air columns were measured by a ground-based multi-channel sunphotometer at the BAPMoN station(36$^{\circ}$31'N, 126$^{\circ}$19'E) in Anmyon Island, Korea, from 1 March 1998 to 31 May 1998. We used the data of three yellow sand and two clear sky days in order to analyze the temporal variations in aerosol optical thickness at the station. The basic aerosol optical thickness generally represented smaller than 0.3 in a clear sky and the range 0.5 to 1.1 in yellow sand. Especially the aerosol optical thickness represented larger than 0.9 in a heavy yellow sand. It was found that the aerosol optical thickness of yellow sand was highly increased in comparison with the case of a clear sky andparticles larger than 0.5$mu extrm{m}$ were also increased in the spectral distribution of aerosol volume during yellow sand. Consequently the spectral variations in tropospheric aerosol caused by yellow sand were determined by the number concentration of particles larger than 0.5${\mu}{\textrm}{m}$ and the magnitude of yellow sand.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.1255-1257
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• 2003

This study proposes a single-channel satellite remote sensing algorithm for retrieving aerosol optical thickness over global ocean using FY-1C/1D data. An efficient lookup table (LUT)method is adopted in this algorithm to generate apparent reflectance in channel 1 and channel 2 of FY-1C/1D over ocean. The algorithm scale the apparent reflectance in cloud-free conditions to aerosol optical thickness using a state-of-art radiative transfer model 6S with input of the relative spectral response of channel 1 and 2 of FY-1C/1D. Monthly mean composite maps of the aerosol optical thickness have been obtained from FY-1C/1D global area coverage data between 2001 and 2003. Aerosol optical thickness maps can show the major aerosol source which are located off the west coast of northern and southern Africa, Arabian Sea and India Ocean. These result is very similar to other satellite sensors such as AVHRR and MODIS in the location area of heavy aerosol optical thickness over global ocean. The algorithm have been used to FY-1D operational performance and it is the first operational aerosol remote sensing product in China.

• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.378-381
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• 2002

We retrieved the aerosol optical thickness $\tau$$_{a}$ over land from Landsat-7/ETM+ image data using the correlation between the visible reflectance and middle IR reflectance. This band correlation method for aerosol retrieval was originally proposed fur MODIS data analysis by Kaufman et al.(1977). The results of retrieved aerosol optical thickness $\tau$$_{a}$ from Landsat-7/ETM+ data were compared with the simultaneous sky observation data at our study site. We found a good agreement between the retrieved and observed values. We presented the distribution maps of the aerosol optical thickness over land, retrieved from Landsat-7/ETM+ image data. Then, the surface reflectance map was also presented. The aerosol optical thickness over sea was retrieved assuming no reflected contribution from sea in the near IR band. In addition, we discussed some limitations when we apply the band correlation method.

• Korean Journal of Remote Sensing
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• v.33 no.5_1
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• pp.607-615
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• 2017

The aerosol optical thickness data retrieved by Moderate Resolution Imaging Spectrometer (MODIS) of Terra & Aqua and Meteorological Imager (MI) of Communication Ocean and Meteorological Satellite (COMS) are analyzed and compared with the measurement data of Aerosol Robotic Network (AERONET) in Northeast Asia. As the result, the aerosol optical thickness retrieved by MODIS and MI were well agreed at ocean region but quite different at cloud edge and barren surface. The reason was that MODIS aerosol optical thickness was retrieved using the visible and infrared channels but MI was retrieved with the visible channel only. Consequentially, the thin cloud be misinterpreted as aerosol by MI and the difference between MODIS and MI aerosol optical thicknesses could be occurred with Normal Distribution Vegetation Index (NDVI) and land surface property. Therefore, the accuracies of clear/cloud region and surface reflectivity are required in order to improve the aerosol optical thickness algorithm by MI.

• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.12-16
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• 2002

The clear sky radiative forcings of aerosols were evaluated over East Asia. We first investigated optical characteristics of aerosol using sky radiation measurements. An algorithm of Nakajima et al. (1996) is used for retrieving aerosol parameters such as optical thickness, ${\AA}$ngstr$\"{O}$m exponent, single scattering albedo, and size distribution from sky-radiation measurements, which then can be used for examining spatial and temporal variations of aerosol. Obtaining aerosol radiative forcing at TOA and surface, a radiative transfer model is used with inputs of obtained aerosol parameters and GMS-5 satellite-based cloud optical properties. Results show that there is a good agreement of simulated downwelling radiative flux at the surface with observation within 10 W m$^{-2}$ rms errors under the clear sky condition. However, a relatively large difference up to 40 W m$^{-2}$ rms error is found under the cloudy sky condition. The computed aerosol radiative forcing at the surface shows downward flux changes ranging from -100 to -170 W m$^{-2}$ per unit aerosol optical thickness at 0.7 $\mu$m. The different values of aerosol radiative forcing among the stations is mainly due to the differences in single scattering albedo ($\omega$$_{0.7}$) and asymmetric parameter (g$_1$) related to the geographical and seasonal variations.

• Atmosphere
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• v.18 no.4
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• pp.287-297
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• 2008

The vertical profiles and optical properties of Asian dust are investigated using ground-based measurements from 1998 to 2002. Vertical profiles of aerosol extinction coefficient are evaluated using MPL (Micro Pulse Lidar) data. Optical parameters such as aerosol optical thickness ($\tau$), ${\AA}ngstr\ddot{o}m$ exponent ($\alpha$), single scattering albedo ($\omega$), refractive index, and volume size distribution are analyzed with sun/sky radiometer data for the same period. We can separate aerosol vertical profiles into three categories. First category named as 'Asian dust case', which aerosol extinction coefficient is larger than $0.15km^{-1}$ and dust layer exists from surface up to 3-4km. Second category named as 'Elevated aerosol case', which aerosol layer exists between 2 and 6km with 1-2.5km thickness, and extinction coefficient is smaller than $0.15km^{-1}$. Third category named as 'Clear sky case', which aerosol extinction coefficient appears smaller than $0.15km^{-1}$. and shows that diurnal variation of background aerosol in urban area. While optical parameters for first category indicate that $\tau$ and $\alpha$ are $0.63{\pm}0.14$, $0.48{\pm}0.19$, respectively. Also, aerosol volume concentration is increased for range of 1 and $4{\mu}m$, in coarse mode. Optical parameters for second category can be separated into two different types. Optical properties of first type are very close to Asian dust cases. Also, dust reports of source region and backward trajectory analyses assure that these type is much related with Asian dust event. However, optical properties of the other type are similar to those of urban aerosol. For clear sky case, $\tau$ is relatively smaller and $\alpha$ is larger compare with other cases. Each case shows distinct characteristics in aerosol optical parameters.

• Asian Journal of Atmospheric Environment
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• v.3 no.1
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• pp.1-8
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• 2009

Enhancement of aerosol optical thickness (AOT) and surface aerosol mass concentration in Korea for an active forest fire episode in Northeast Asia were estimated by Community Multi-scale Air Quality (CMAQ) model. MODIS/TERRA remote detects of fires in Northeast Asia for May 2003 gave a constraint for estimation of wildfire emissions with an NDVI distribution for recent five years. The simulated wildfire plumes and enhancement of AOT were evaluated and well resolved by comparing multiple satellite observations such as MODIS, TOMS, and others. Scatter plots of observed daily mean aerosol extinction coefficient versus $PM_{10}$ concentration in ground level in Korea showed distinctively different trends based on the ambient relative humidity.

• Journal of Korean Society for Atmospheric Environment
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• v.32 no.1
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• pp.57-66
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• 2016

Aerosol optical thickness (AOT) and ${\AA}ngstr{\ddot{o}}m$ exponents were monitored at the KIU site ($N35.91^{\circ}$, $E128.80^{\circ}$) during the continuous observation period of 5 November 2010~19 March 2013 using a Microtops-II handheld munti-wavelenth radiometer. Comparisons of AOT values from the Microtops-II with the Sun-sky radiometer data from the Aerosol Robotic Network (AERONET) showed very good agreements: correlation coefficients are lies between 0.98 and 0.99, slopes range from 0.98 to 1.01, and intercepts are smaller than 0.008 at five wavelengths (380 nm, 440 nm, 500 nm, 675 nm, 870 nm). During the observation period, the Microtops-II AOT and ${\AA}ngstr{\ddot{o}}m$ exponents are ${\tau}_{500}=0.560{\pm}0.351$, ${\alpha}_{500-870}=1.135{\pm}0.445$. Fine mode aerosols appear to dominate in the study region with significant contributions from small particles.

• Proceedings of the KSRS Conference
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• 1999.11a
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• pp.100-102
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• 1999

We have analyzed AVHRR global data set for obtaining aerosol and cloud microphysical parameters, i. e., optical thickness and size index of particle polydispersions. From the results, it is found that the cloud optical thickness increases with increasing aerosol column number, which seems to be caused mainly by decreasing cloud particle radius, The cloud liquid water path was observed to be relatively constant without a significant dependence on the aerosol number. Further comparison of the satellite results with a general circulation model simulation.