• Journal of Korean Society for Atmospheric Environment
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• v.20 no.E2
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• pp.61-68
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• 2004

Aerosol losses in a 100L Tedlar$^{(R)}$ bag were investigated for the aerosols with number median diameter of 0.05 ${\mu}{\textrm}{m}$ and number concentration of 6.4 ${\times}$ 10$^4$ cm$^{-3}$ . Over a 1 hr period, loss of particles in the bag is apparent, and the volume decrease with time is significant. The number concentration, surface area, and volume concentration of the aerosols decreased to 34, 50, and 52% of the initial value in 30 min, respectively. This indicates that deposition to the walls was the main loss process for aerosols in the Tedlar$^{(R)}$ bag. Theoretical calculations showed that coagulations and deposition by diffusion and gravitational sedimentation would not change aerosol characteristics significantly, and the electrical force was the dominant loss process for particles in the Tedlar$^{(R)}$ bag over a 1 hr period.eriod.

• Journal of ILASS-Korea
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• v.3 no.4
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• pp.25-34
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• 1998

Hygroscopic aerosols can rapidly grow in size by steam condensation even under subsaturated steam conditions. Much efforts have been made to handle this process, but there have been computational difficulties in handling the condensational growth of hygroscopic aerosols by contentional methods. A recently released computer code, CONTAIN 2.0, employs a new technique called Moving Sectional Method(MSM) to handle the growth of hygroscopic aerosols. As a part of the model verification efforts, we have used the code to simulate the VANAM M3U hygroscopic aerosol experiment. We assess the accuracies of the new MSM and the conventional Fixed Sectional Method(ESM) based on the simulation results. Also presented are discussions about the robustness of the MSM.

• Nuclear Engineering and Technology
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• v.55 no.11
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• pp.3935-3939
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• 2023

The paper presents the results of a study of radioactive noble gases and from decay products in the atmosphere of the reactor hall of the research nuclear reactor IVV-2M. The distribution of short-lived ⁸⁸Rb and ¹³⁸Cs activity by sizes of aerosol particles was measured in the range of 0.5-1000 nm. It is shown that radioactive aerosols are characterized by three main modes with AMTD 2-3 nm, 7-15 nm and 400 nm. About 70% of aerosol activity is due to ⁸⁸Rb. The equilibrium factor between ⁸⁸Kr and ⁸⁸Rb is 0.2 ± 0.1. The total concentration of aerosols particles was measured using an aerosol diffusion spectrometer. The value of unattached fraction of radioactive aerosols in the atmosphere of reactor hall IVV2M was f = 0.15-0.25 at the average total aerosol particles concentration from 20,000 cm³ to 53,000 cm³.

• Journal of Korean Society for Atmospheric Environment
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• v.22 no.1
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• pp.1-14
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• 2006

Tropospheric aerosols are highly variant in time and space due to non-uniform source distribution and strong influence of meteorological conditions. Backscatter lidar measurement is useful to understand vertical distribution of aerosol. However, the backscatter lidar equation is undetermined due to its dependence on the two unknowns, extinction and backscattering coefficient. This dependence necessitates the exact value of the ratio between two parameters, that is, the lidar ratio. Also, Iidar ratio itself is useful optical parameter to understand properties of aerosols. Tropospheric aerosols were observed to understand variance of lidar ratio at Anmyeon island ($36.32^{/circ}N$, $126.19^{/circ}E$), Korea using a multi-wavelength raman lidar system developed by the Advanced Environmental Monitoring Research Center (ADEMRC), Gwangju Institute Science and Technology (GIST), Korea during measurement periods; March 15$\sim$April $16^{th}$, 2004 and May 24$\sim$ $8^{th}$ 2005. Extinction coefficient, backscattering coefficient, and lidar ratio were measured at 355 and 532 nm by the Raman method. Different types of aerosol layers were distinguished by the differences in the optical properties such as Angstrom exponent, and lidar ratio. The average value of lidar ratio during two observation periods was found to be $50.85\pm4.88$ sr at 355 nm and $52.43\pm15.15$ sr at 532 nm at 2004 and $57.94\pm10.29$ sr at 355 nm and $82.24\pm15.90$ sr at 532 nm at 2005. We conduct hysplit back-trajectory to know the pathway of airmass during the observation periods. We also calculate lidar ratio of different type of aerosol, urban, maritime, dust, continental aerosols using OPAC (Optical Properties of Aerosols and Clouds), Remote sensing of atmospheric aerosol using a multi-wavelengh lidar system with Raman channels is quite and powerful tool to characterize the optical propertises of troposheric aerosols.

• Korean Journal of Remote Sensing
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• v.21 no.4
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• pp.273-285
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• 2005

This study has investigated the suitable wavelength for detecting biomass burning aerosols. We have performed the analysis of the wavelength at 380nm in near-UV, 400nm, 412nm, 460nm, and 490nm in visible, and 2100nm in shortwave infrared regions from the Global Imager measurements. It is well known that the UV bands have the advantage of the aerosols retrieval due to the low surface reflectance and a weak effect of Bidirectional Reflectivity Distribution Function. However, the pure surface reflectances of shortwave visible bands, except 412nm, are as low as that of 380nm in near-UV over northeast Asia. In order to detect the aerosol signal, we have retrieved the aerosol reflectance as a function of wavelength based on the surface reflectivity contrast method for the period of May 2003. It is interesting that the retrieved aerosol reflectance with 460nm is slightly more sensitive than that with 380nm. Additionally, we have applied the TOMS aerosol index method to determine the best pair for biomass burning aerosols and found that the pair of 380 and 460nm results in the best signal for retrieving aerosols.

• Journal of Korean Society for Atmospheric Environment
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• v.26 no.5
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• pp.554-566
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• 2010

We present optical and microphysical particle properties of aerosol retrieved by multi-wavelength Raman lidar at Anmyun island ($36.32^{\circ}N$, $126.19^{\circ}E$), Korea. The results present aerosol properties in various height layers of the atmospheric pollution layers observed over the Korean peninsula on eight consecutive days (27, 28, 29, 30 and 31 May, 4, 5 and 7 June) in 2005 at Anmyun island. We found anthropogenic pollution on 27, 28, and 29 May and local haze on other measurement days. The origin of the particle plumes was determined by simulations of FLEXPART. The source regions of the particles resulted in rather clear differences between the optical and microphysical properties of the pollution layers. The single-scattering albedo of anthropogenic aerosols from China ($0.91{\pm}0.01$ at 532 nm) were lower than the single-scattering albedo of local haze aerosols ($0.95{\pm}0.01$ at 532 nm). Local haze aerosols show larger effective radii of $0.24{\pm}0.02\;{\mu}m$ at relative humidity of 55~75%. The effective radii of anthropogenic aerosols are $0.20{\pm}0.2\;{\mu}m$ and $0.27\;{\mu}m$ at relative humidity of 25~50%.

• Atmosphere
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• v.20 no.4
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• pp.483-494
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• 2010

The vertical profiles of the extinction coefficient, the backscatter coefficient, and the lidar ratio (i.e., extinction-to-backscattering ratio) for Asian dust and pollution aerosols are determined from Raman (inelastic) and elastic backscatter signals. The values of lidar ratios during two polluted days is found between 52 and 82 sr (July 22, 2009) and 40~60 sr (July 31, 2009) at 52 nm, with relatively low value of particle depolarization ratio (<5%) and high value of sun photometer-derived Angstrom exponent (> 1.2). However, lidar ratios between 25 and 40 sr are found during two Asian dust periods (October 20, 2009 and March 15, 2010), with 10~20% of particle depolarization ratio and the relatively low value of sun photometer-derived Angstrom exponent (< 0.39). The lidar ratio, particle depolarization ratio and color ratio are useful optical parameter to distinguish non-spherical coarse dust and spherical fine pollution aerosols. The comparison of aerosol extinction profiles determined from inelastic-backscatter signals by the Raman method and from elastic-backscatter signals by using the Fernald method with constant value of lidar ratio (50 sr) have shown that reliable aerosol extinction coefficients cannot be determined from elastic-backscatter signals alone, because the lidar ratio varies with aerosol types. A combined Raman and elastic backscatter lidar system can provide reliable information about the aerosol extinction profile and the aerosol lidar ratio.

• Journal of Korean Society for Atmospheric Environment
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• v.17 no.E1
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• pp.1-7
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• 2001

The elemental characteristics of atmospheric aerosols were investigated as a function of particle size and water solubility. The aerosol particles were samples at 12 individual size ranges between 0.01 and 30㎛. Collected aerosol particles were separated into both soluble and insoluble components. The concentrations of 15 elements in both components were determined by a PIXE analysis using a 2.0 MeV-proton beam. In general, the mass size distribution of particulate matter was represented as a bimodal distribution. The maximum rations of S in July and December were 5.5 and 3.8 %, and they appeared in the size range of 0.47∼1.17㎛(stage No. 6 or 7) . The ratios of a S at non-separated size were 3.1 and 2.2 % in July and December, respectively, On the other hand, the maximum rations of Si in July and December were 7.0 and 5.4% and they appeared in the size range of 5.1∼30㎛(stage No. 0∼2). The ratios of Si at the non-separated size were 2.1 and 1.8% in July and December, respectively, The mass diameter of 12 elements ranged between 0.59㎛ of S and 3.20 of Fe. More than 90% of atmospheric aerosols consisted of the light elements such as C, N, O, H and Al. The soluble component was dominant in the smaller size range and the insoluble component in the larger size range. Large portions of Si. Ti and Fe existed in insoluble state. By contrast, S, Cl, Ca, Zn and Br were dissolved in water.

• Proceedings of the KSRS Conference
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• v.1
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• pp.467-470
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• 2006

Geostationary Ocean Color Imager (GOCI) onboard its Communication Ocean and Meteorological Satellite (COMS) is scheduled for launch in 2008. GOCI includes the eight visible-to-near-infrared (NIR) bands, 0.5km pixel resolution, and a coverage region of 2500 ${\times}$ 2500km centered at 36N and 130E. GOCI has had the scope of its objectives broadened to understand the role of the oceans and ocean productivity in the climate system, biogeochemical variables, geological and biological response to physical dynamics and to detect and monitor toxic algal blooms of notable extension through observations of ocean color. To achieve these mission objectives, it is necessary to develop an atmospheric correction technique which is capable of delivering geophysical products, particularly for highly turbid coastal regions that are often dominated by strongly absorbing aerosols from the adjacent continental/desert areas. In this paper, we present a more realistic and cost-effective atmospheric correction method which takes into account the contribution of NIR radiances and include specialized models for strongly absorbing aerosols. This method was tested extensively on SeaWiFS ocean color imagery acquired over the Northwest Pacific waters. While the standard SeaWiFS atmospheric correction algorithm showed a pronounced overcorrection in the violet/blue or a complete failure in the presence of strongly absorbing aerosols (Asian dust or Yellow dust) over these regions, the new method was able to retrieve the water-leaving radiance and chlorophyll concentrations that were consistent with the in-situ observations. Such comparison demonstrated the efficiency of the new method in terms of removing the effects of highly absorbing aerosols and improving the accuracy of water-leaving radiance and chlorophyll retrievals with SeaWiFS imagery.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.6 no.3
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• pp.237-246
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• 1994

Experimental data are reported for charging and collection of NaCl aerosols in the 0.03- to $0.2{\mu}m$-geometric-mean-diameter range in 2-stage parallel-plate electrostatic precipitators. The NaCl aerosols are generated with geometric standard deviation of about 1.74 and particle generation rate of about 10^9 particles/see by the constant output atomizer and injected into the air flow in the clean wind-tunnel. The 2-stage parallel-plate electrostatic precipitator installed in the test section of the wind-tunnel is operated with a positive corona discharge. The NaCl aerosols in the channel flow are sampled and transported to the aerosol particle number concentration measurement system by using the isoaxial sampling and transport system constructed based on the Okazaki and Willeke design. The aerosol particle number concentration measurement system measures the size distribution of submicrometer aerosols by an electrical mobility detection technique. It is confirmed from comparing the measured collection efficiencies in this study and the predicted ones by our previous theoretical analysis that the predicted collection efficiencies agree well with the experimental ones. It is also found from the comparison that below about $0.02{\mu}m$ all particles are not charged and the uncharged particles are not collected, and consequently 2-stage parallel-plate electrostatic precipitators are not suitable for that particle size range.