• Journal of the Korean Association of Geographic Information Studies
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• v.16 no.2
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• pp.141-151
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• 2013

This study presents a modeling of aerosol extinction vertical profiles in Korea by using the Moderate Resolution Imaging Spectro-radiometer(MODIS) derived aerosol optical thickness(AOT) and ground based visibility observation data. The method uses a series of physical equations for the derivation of aerosol scale height and vertical profiles from MODIS AOT and surface visibility data. The modelled results under the standard atmospheric condition showed small differences with the standard aerosol vertical profile used in the radiative transfer model. Model derived aerosol scale heights for two cases of clean(${\tau}_{MODIS}=0.12{\pm}0.07$, visibility=$21.13{\pm}3.31km$) and hazy atmosphere(${\tau}_{MODIS}=1.71{\pm}0.85$, visibility=$13.33{\pm}5.66km$) are $0.63{\pm}0.33km$ and $1.71{\pm}0.84km$. Based on these results, aerosol extinction profiles can be estimated and the results are transformed into the KML code for visualization of dataset. This has implications for atmospheric environmental monitoring and environmental policies for the future.

• Journal of the Optical Society of Korea
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• v.14 no.3
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• pp.221-227
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• 2010

Aerosol size distribution provides good information for predicting weather changes and understanding cloud formation. Aerosol extinction coefficient and backscattering coefficient are measured by many scientists, but these parameters depend not only on aerosol size but on aerosol concentrations. An algorithm has been developed to measure aerosol parameters such as ${\AA}$ngstr$\ddot{o}$m exponent, color ratio, and LIDAR ratio without any assumptions by using two wavelength rotational Raman LIDAR signals. These parameters are good indicators for the aerosol size. And we can find ${\AA}$ngstr$\ddot{o}$m exponent, color ratio, and LIDAR ratio under various weather conditions. Finally, it can be seen that the ${\AA}$ngstr$\ddot{o}$m exponent has an inverse relationship to the particle size of the aerosol and the color ratio is linearly dependent on the aerosol size. An ${\AA}$ngstr$\ddot{o}$m exponent from 1.2 to 3.1, a color ratio from 0.28 to 1.04, and a LIDAR ratio 66.9 sr at 355 nm and 32.6 sr at 532 nm near the cloud were obtained.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2006.10a
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• pp.158-160
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• 2006

• Korean Journal of Optics and Photonics
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• v.33 no.1
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• pp.1-10
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• 2022

In this study we introduce a new method for high-spatial-resolution continuous wave (CW) aerosol lidar that has a high spatial resolution in the near field and a low spatial resolution at long distances. A normal lidar system uses a nanosecond-pulse laser and measures the round-trip TOF between the aerosol and laser to obtain range resolution. In this study, however, we propose a new type of spatially resolving aerosol lidar that uses laser-scattering images. Using a laser-light-scattering image, we have calculated the distance of each scattering aerosol image for a given pixel, and recovered the short-range aerosol extinction. For this purpose, we have calculated the distance image and the contribution range of the aerosol to the given one-pixel image, and finally we have calculated the extinction coefficients of the aerosol with range-resolved information. In the case of traditional aerosol lidar, we can only obtain the aerosol extinction coefficients above 400 m. Using our suggested method, it was possible to extend the range of the extinction coefficient lower then several tens of meters. Finally, we can remove the unknown short-range region of pulsed aerosol lidar using our method.

• Current Optics and Photonics
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• v.2 no.1
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• pp.15-22
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• 2018

To measure atmospheric temperature, water vapor, and aerosol simultaneously, an efficient multi-function Raman lidar using an ultraviolet-wavelength laser has been developed. A high-performance spectroscopic box that utilizes multicavity interference filters, mounted sequentially at small angles of incidence, is used to separate the lidar return signals at different wavelengths, and to extract the signals with high efficiency. The external experiments are carried out for simultaneous detection of atmospheric temperature, water vapor, and aerosol extinction coefficient in Beijing, under clear and hazy weather conditions. The vertical profiles of temperature, water vapor, and aerosol extinction coefficient are analyzed. The results show that for an integration time of 5 min and laser energy of 200 mJ, the mean deviation between measurements obtained by lidar and radiosonde is small, and the overall trend is similar. The statistical temperature error for nighttime is below 1 K up to a height of 6.2 km under clear weather conditions, and up to a height of 2.5 km under slightly hazy weather conditions, with 5 min of observation time. An effective range for simultaneous detection of temperature and water vapor of up to 10 km is achieved. The temperature-inversion layer is found in the low troposphere. Continuous observations verify the reliability of Raman lidar to achieve real-time measurement of atmospheric parameters in the troposphere.

• Korean Journal of Remote Sensing
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• v.30 no.5
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• pp.559-570
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• 2014

Backscatter signal observed from the space-borne Light Detection And Ranging (LIDAR) system is providing unique 3-dimensional spatial distribution as well as temporal variations for atmospheric aerosols. In this study, the continuous observations for aerosol profiles were analyzed during a years of 2012 by using a Cloud-Aerosol LIDAR with Orthogonal Polarization (CALIOP), carried on the Cloud-Aerosol LIDAR and Infrared Pathfinder Satellite Observation (CALIPSO) satellite. The statistical analysis on the particulate extinction coefficient and depolarization ratio for each altitude was conducted according to time and space in order to estimate the variation of optical properties of aerosols over Northeast Asia ($E110^{\circ}-140^{\circ}$, $N20^{\circ}$ $-50^{\circ}$). The most frequent altitudes of aerosols are clearly identified and seasonal mean aerosol profiles vary with season. Since relatively high particle depolarization ratios (>0.5) are found during all seasons, it is considered that the non-spherical aerosols mixed with pollution are mainly exists over study area. This study forms initial regional 3-dimensional aerosol information, which will be extended and improved over time for estimation of aerosol climatology and event cases.

• Journal of Korean Society for Atmospheric Environment
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• v.12 no.4
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• pp.407-419
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• 1996

Characteristics of visual air quality in Seoul have been investigated between June 13 and 21, 1994. Optical properties (extinction coefficient and particle scattering coefficient), meteorological parameters (relative humidity, temperature, wind speed, wind direction, and cloud cover), particle characteristics (mass size distribution, components) were measured and analyzed. During measurement periods, northwest wind with less than 2m/sec of wind speed deteriorates visibility. Effects of relative humidity are though to be not a direct factor which influence to visibility through the size change due to hygroscopic species in aerosol. During the smoggy period both the aerosol mass concentration and fine particle fraction of the size distribution are increased compared to the clear period. Sulfate, organic carbon, and elemental carbon in aerosol are the major species in determining the occurrence and severity of a smog in Seoul.

• 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.29 no.3
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• pp.264-274
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• 2013

This study investigates long-term trends and characteristics of aerosol light scattering coefficient at Seoul and Baengnyeongdo in order to understand aerosol optical and radiative properties around Korea. The analysis period is limited to one year of 2011. First, the aerosol scattering coefficients (${\sigma}_{sp}$) of both sites show strong linear dependence on the $PM_{2.5}$ mass concentrations with significant correlations between both. Further, correlations and sensitivity between ${\sigma}_{sp}$ and $PM_{2.5}$ increase with relative humidity, implying both relationships are strongly dependent upon moisture amounts in the atmosphere. This study applied 3-step careful quality control procedures to the analysis of ${\sigma}_{sp}$ for the insurance of data confidence. For the relationship analysis of extinction coefficients (${\sigma}_{ext}$) to visibility and aerosol optical depth, ${\sigma}_{sp}$ observed at 3 p.m. have been used with help of aerosol absorption coefficients (${\sigma}_{ap}$) in order to remove its dependence upon relative humidity, and also those of rainy period have been excluded. As expected, ${\sigma}_{ext}$ estimated are inversely proportional to visibility observation by eye. Finally, aerosol extinction coefficients have been vertically integrated with an assumption of nearly well-mixed within an e-folding height to determine aerosol optical depth, and compared with those retrieved from sunphotometer. The results show a reasonable agreement in spite of an inherent difference of each definition. We expect these findings would help to eventually understand aerosol radiative forcing and its effect on the regional climate change around Korea.

• Korean Journal of Remote Sensing
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• v.32 no.2
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• pp.119-131
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• 2016

Descriptions are provided of the automated aerosol-type classification and mass concentration calculation algorithm for real-time data processing and aerosol products in Korea Aerosol Lidar Observation Network (KALION, http://www.kalion.kr). The KALION algorithm provides aerosol-cloud classification and three aerosol types (clean continental, dust, and polluted continental/urban pollution aerosols). It also generates vertically resolved distributions of aerosol extinction coefficient and mass concentration. An extinction-to-backscatter ratio (lidar ratio) of 63.31 sr and aerosol mass extinction efficiency of $3.36m^2g^{-1}$ ($1.39m^2g^{-1}$ for dust), determined from co-located sky radiometer and $PM_{10}$ mass concentration measurements in Seoul from June 2006 to December 2015, are deployed in the algorithm. To assess the robustness of the algorithm, we investigate the pollution and dust events in Seoul on 28-30 March, 2015. The aerosol-type identification, especially for dust particles, is agreed with the official Asian dust report by Korean Meteorological Administration. The lidar-derived mass concentrations also well match with $PM_{10}$ mass concentrations. Mean bias difference between $PM_{10}$ and lidar-derived mass concentrations estimated from June 2006 to December 2015 in Seoul is about $3{\mu}g\;m^{-3}$. Lidar ratio and aerosol mass extinction efficiency for each aerosol types will be developed and implemented into the KALION algorithm. More products, such as ice and water-droplet cloud discrimination, cloud base height, and boundary layer height will be produced by the KALION algorithm.