• Atmosphere
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• v.28 no.2
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• pp.211-222
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• 2018

Cloud droplet activation process is well described by $K{\ddot{o}}hler$ theory and several parameterizations based on $K{\ddot{o}}hler$ theory are used in a wide range of models to represent this process. Here, we test the two different method of calculating the solute effect in the $K{\ddot{o}}hler$ equation, i.e., osmotic coefficient method (OSM) and ${\kappa}-K{\ddot{o}}hler$ method (KK). To do that, each method is implemented in the cloud droplet activation parameterization module of WRF-CHEM (Weather Research and Forecasting model coupled with Chemistry) model. It is assumed that aerosols are composed of five major components (i.e., sulfate, organic matter, black carbon, mineral dust, and sea salt). Both methods calculate similar representative hygroscopicity parameter values of 0.2~0.3 over the land, and 0.6~0.7 over the ocean, which are close to estimated values in previous studies. Simulated precipitation, and meteorological variables (i.e., specific heat and temperature) show good agreement with reanalysis. Spatial patterns of precipitation and liquid water path from model results and satellite data show similarity in general, but on regional scale spatial patterns and intensity show some discrepancy. However, meteorological variables, precipitation, and liquid water path do not show significant differences between OSM and KK simulations. So we suggest that the relatively simple KK method can be a good alternative to the OSM method that requires various information of density, molecular weight and dissociation number of each individual species in calculating the solute effect.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.4
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• pp.35-41
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• 2019

Contrail is a kind of cloud that is formed during the flight by vapor condensation of engine exhaust in a cold atmospheric condition. Owing to the negative effects of contrails on the environment and in military applications, several studies for contrail mitigation had been performed in developed countries. The goal of this research is to design a lab-scale contrail generator, and to validate the contrail mitigation technology suggested by previous studies. The contrail generator was made using superheated vapor and a low temperature wind tunnel. Using this generator, the ineffectiveness of ethanol and surfactant suggested in the previous paper on contrail mitigation was found experimentally.

• Asian Journal of Atmospheric Environment
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• v.4 no.3
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• pp.115-140
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• 2010

Great concerns about atmospheric aerosols are attributed to their multiple roles to atmospheric processes. For example, atmospheric aerosols influence global climate, directly by scattering or absorbing solar radiations and indirectly by serving as cloud condensation nuclei. They also have a significant impact on human health and visibility. Many of these effects depend on the size and composition of atmospheric aerosols, and thus detailed information on the physicochemical properties and the distribution of airborne particles is critical to accurately predict their impact on the Earth's climate as well as human health. A single particle analysis technique, named low-Z particle electron probe X-ray microanalysis (low-Z particle EPMA) that can determine the concentration of low-Z elements such as carbon, nitrogen and oxygen in a microscopic volume has been developed. The capability of quantitative analysis of low-Z elements in individual particle allows the characterization of especially important atmospheric particles such as sulfates, nitrates, ammonium, and carbonaceous particles. Furthermore, the diversity and the complicated heterogeneity of atmospheric particles in chemical compositions can be investigated in detail. In this review, the development and methodology of low-Z particle EPMA for the analysis of atmospheric aerosols are introduced. Also, its typical applications for the characterization of various atmospheric particles, i.e., on the chemical compositions, morphologies, the size segregated distributions, and the origins of Asian dust, urban aerosols, indoor aerosols in underground subway station, and Arctic aerosols, are illustrated.

• Ocean and Polar Research
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• v.23 no.4
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• pp.401-410
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• 2001

Global climate change will alter many such properties of the Southern Ocean as temperature, circulation, stratification, and sea-ice extent. Such changes are likely to influence the species composition and activity of Antarctic marine microorganisms (protists and bacteria) which playa major role in deter-mining the concentration of atmospheric $CO_2$ and producing precursors of cloud condensation nuclei. Direct impacts of climate change on Antarctic marine microorganisms have been determined for very few species. Increasing water temperature would be expected to result in a southward spread of pelagic cyanobacteria, coccolithophorids and others. Growth rates of many species would be expected to increase slightly but nutrient limitation, especially micronutrients, is likely to result in a negligible increase in biomass. The extent of habitats would be reduced for those organisms presently living close to the upper limit of their thermal tolerance. Increased UVB irradiance is likely to favour the growth of those organisms tolerant of UVB and may change the trophic structure of marine communities. Indirect effects, especially those as a consequence of a diminution of the amount of sea-ice and increased upper ocean stratification, are predicted to lead to a change in species composition and impacts on both trophodynamics and vertical carbon flux.

• Journal of Aerospace System Engineering
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• v.12 no.2
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• pp.23-29
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• 2018

Contrail is type of clouds which are formed by a condensation of water vapour from the aircraft exhaust when the aircraft is flying the cold atmosphere. Since contrails have considerable effect on greenhouse-effect and military stealth efficiency, researches about contrail avoidance technology has been conducted for decades. However, none of the previous researches concerning contrail avoidance was carried out in Korea. Thus, review of the previous study regarding contrail reduction is absolutely needed. In this paper, researches conducted by several countries are categorically introduced, and practicabilities of their methods are analyzed. This paper also suggests some practical and systematized way to conduct future researches about contrail avoidance.

• Korean Chemical Engineering Research
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• v.48 no.1
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• pp.20-26
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• 2010

Water soluble organic and inorganic species are important components in atmospheric aerosol particles and may act as cloud condensation nuclei to indirectly affect the climate. To characterize organic and elemental carbon(OC and EC), water-soluble organic carbon(WSOC) and inorganic ionic species contents, daily $PM_{2.5}$ measurements were made during the wintertime at an urban site of Gwangju. Average concentrations of WSOC, $NO_3^-$, $SO_4^{2-}$ and $NH_4^+$, which are major components in the water-soluble fraction in PM2.5, are 2.11, 5.73, 3.51 and $3.31{\mu}g/m^3$, respectively, representing 12.0(2.9~23.9%), 21.0(12.9~37.6%), 11.6(2.5~25.9%) and 11.7%(3.8~18.6%) of the $PM_{2.5}$, respectively. Abundance of water soluble organic compounds ranged from 5.4 to 35.9% of total water soluble organic and inorganic components with a mean of 17.6%. Even though the sampling was performed during the winter, the average contributions of secondary OC and WSOC, as deduced from primary OC/EC(or WSOC/EC) ratio, were relatively high, accounting for 17.9%(0~44.4%) of the total OC and 11.2%(0.0~51.4%) of the total WSOC, respectively. During the sampling period, low $SO_4^{2-}/(SO_4^{2-}+SO_2$) ratio of 0.14(0.03~0.32) and relative humidity condition in the winter time suggest an possibility of impact of long-range transport and/or aqueous transformation processes such as metal catalyzed oxidation of sulfur, in-cloud processes, etc.