Soon-chang Yoon | Seoul National University (original) (raw)

Papers by Soon-chang Yoon

Asia Pacific Journal of Atmospheric Sciences, Oct 1, 1988

Aeolian Research, 2011

The dust cycle is an integral part of the Earth system. Each year, an estimated 2000Mt dust is em... more The dust cycle is an integral part of the Earth system. Each year, an estimated 2000Mt dust is emitted into the atmosphere, 75% of which is deposited to the land and 25% to the ocean. The emitted and deposited dust participates in a range physical, chemical and bio-geological processes that interact with the cycles of energy, carbon and water. Dust

An unarmored dinoflagellate Cochlodinium polykrikoides has formed red tides responsible for fish ... more An unarmored dinoflagellate Cochlodinium polykrikoides has formed red tides responsible for fish mass mortalities especially in coastal areas of western Japan and southern Korea almost every summer to autumn. In laboratory culture, the optimum temperature for growth of the species is ca. 27 8C. Since the species cannot survive in water of temperatures of less than 10 8C, it was considered to over-winter in some certain regions as a motile form or resting cyst, and expand its distribution after the temperature increases to a level tolerable for growth. To determine the over-wintering regions and migration pattern of C. polykrikoides, occurrences of the motile cells were surveyed in the coastal and offshore areas of western Kyushu, Japan and south coast of the Korean Peninsula from April 2006 to August 2008. Cells of C. polykrikoides were found at 14 sites during the investigated period. Motile cells occurred throughout the year in Usuka Bay, Hirado of West Japan. From offshore regions of the Goto Islands and off Shin-Nagasaki Fishing Port, motile cells of C. polykrikoides were first detected from late May, and continuously occurred until February in Nama Bay of the Kami-Goto Islands. This first appearance was before red tides of C. polykrikoides reported at coastal areas in western Kyushu. In Korea, this species was first observed in May and disappeared after October in 2007. These occurrence patterns imply that Usuka Bay in Hirado is one of the over-wintering regions in western Kyushu, and also this species is possibly transported into the northern part of the East China Sea by the Tsushima Warm Current every year.

Journal of Korean Society for Atmospheric Environment

A case study was conducted for a severe wintertime dust event that occurred on December 29, 2007 ... more A case study was conducted for a severe wintertime dust event that occurred on December 29, 2007 in Korea. Three different dust emission schemes, namely, those of Marticorena and Bergametti (1995), Lu and Shao (1999), and Shao (2004) (hereinafter, referred to MB, LS, and S04 schemes, respectively) were implemented in Weather Research Forecast with Chemistry (WRF/Chem) to assess their performance in simulating wintertime Asian dust events. WRF/Chem simulation reproduces dust emission over Mongolia on December 27 and 28, 2007 and the onset timing of the dust event in Korea well. There is, however, a huge difference among the estimated dust emission amounts for the three schemes; the dust concentration derived by MB scheme is 6 times larger than that from LS scheme. The three schemes overestimate dust concentrations when comparing to observed surface-level PM 10 mass concentrations in Ganghwa, Seoul, and Yeongwol. This discrepancy is thought to be mainly due to the overestimated model winds and the surface condition such as snow cover fraction, which did not adequately represent the real conditions. Considering frozen soil effect on dust emission, the model results are comparable with observation data: it is important to consider frozen soil in simulating wintertime dust events.

Air Quality, Atmosphere & Health

Atmospheric Chemistry and Physics Discussions

A bin-based meso-scale cloud model has been employed to explore the aerosol influence on the clou... more A bin-based meso-scale cloud model has been employed to explore the aerosol influence on the cloud microphysical properties and precipitation efficiency of shallow stratocumulus in East Asia in March 2005. We newly constructed aerosol size distributions and hygroscopicity parameters for five aerosol species that reproduced observed

Proceedings of Spie the International Society For Optical Engineering, 2003

In order to investigate the characteristic of optical properties of Asian dust particles, the atm... more In order to investigate the characteristic of optical properties of Asian dust particles, the atmospheric aerosol vertical profile was measured with the multi-wavelength LIDAR system, at the Gosan super site (33 • 17 N, 126 • 10 E) in Jeju Island, Korea, during the ACE-Asia intensive observation period, 11 March-4 May 2001. An air mass backward trajectory analysis, using Hysplit-4, was carried out to track the aerosol plume, with high mass loading, from the Chinese desert regions during the period of Asian dust storm events. Vertical atmospheric aerosol profiles on three major Asian dust storm event days, 22 March and 13 and 26 April 2001, have been analyzed. The LIDAR-derived aerosol optical depth values were compared with those measured by a collocated sunphotometer.

Journal of Korean Society for Atmospheric Environment, 2007

Journal of Korean Society for Atmospheric Environment, 2013

Journal of Korean Society for Atmospheric Environment, 2010

Journal of Korean Society for Atmospheric Environment, 2012

Journal of Geophysical Research: Atmospheres, 2013

ABSTRACT The Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) aerosol optical depth (AOD... more ABSTRACT The Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) aerosol optical depth (AOD) has been compared with the Moderate Resolution Imaging Spectroradiometer (MODIS)-Aqua AOD using Level 2 products of both instruments. Such comparisons have been performed for five different aerosol subtypes classified by CALIOP algorithm, namely clean marine, dust, polluted dust, polluted continental, and biomass burning, over the ocean from June 2006 to December 2010.MODIS AOD at 550 nm(0.111 ± 0.079) for the collocated data pairs is about 63% higher than CALIOP AOD at 532nm (0.068 ± 0.073). For clean marine,MODIS AOD(0.110 ± 0.064) is almost twice the CALIOPAOD (0.056 ± 0.038), and the difference between the AOD values has a strong latitude dependence likely related to the surface wind speed over the ocean. The difference in AOD for dust (13%) is observed to be the lowest among the five aerosol types under consideration, but it shows a slight regional variation. The discrepancy of AOD for dust also shows strong dependency on the layer mean of the particulate depolarization ratio. CALIOP AOD is higher than MODIS AOD for both polluted dust and polluted continental by 15% and 29%, respectively, for most of the ocean. One of the possible reasons for the difference is the misclassification of clean marine (or marine + dust) as polluted dust and polluted continental in the CALIOP algorithm. For biomass burning, uncertainty in the layer base altitude is thought to be one of the main reasons for the lower value of CALIOP AOD.

Meteorology and Atmospheric Physics, 2014

ABSTRACT Under cloudy conditions at the Gosan Climate Observatory (GCO), Korea, we observed disti... more ABSTRACT Under cloudy conditions at the Gosan Climate Observatory (GCO), Korea, we observed distinct new particle formation and growth (NPF) events from simultaneous co-located measurements of aerosol and cloud profiles, cloud cover, shortwave radiation, and the number concentration and size distribution of aerosols. The high frequency of NPF was observed at GCO under decreased downwelling solar radiation caused by clouds. Although we observed about 15 and 40 % decreases in downwelling surface shortwave radiations, in the presence of thick mid-level (low-level) clouds, on January 28 and 30, 2012, respectively, distinct NPFs with a growth rate of 3.3 (3.9) nm h(-1) were observed. We examined a 4-year series (May 2008 to April 2012) of continuous measurements of the size distribution of aerosol numbers and visually observed cloud cover. We found that approximately 13 % (i.e., 35 days out of 280 days) of total NPF events were observed under cloud-free conditions (i.e., cloud cover of 0/10). About 20 % (i.e., 57 days out of 280 days) of total NPF events occurred under mostly overcast conditions (i.e., cloud cover of 9/10-10/10). Although NPF events occurring under cloudy conditions were also found elsewhere, the frequency of NPF occurring at GCO seems much higher. The average value of relative humidity for the strong-NPF event days is lower than that of the weak and non-NPF event days for all cloud categories. No significant difference in the condensation sink was found among strong-, weak-, and non-NPF days, but the condensation sink showed a slight decreasing tendency with increasing cloudiness. Further investigations on precursor gases and preexisting aerosols under cloudy conditions are needed.

Science of The Total Environment, 2010

In this study, we investigate the transport of dust particles, its vertical distribution, and the... more In this study, we investigate the transport of dust particles, its vertical distribution, and the associated meteorological conditions during an Asian dust event that was observed in Seoul, Korea on May 29-31, 2008. This study analyzes data from ground-based and space-borne 2-wavelength polarization lidars, particulate mass concentrations, and synoptic weather data. Surface meteorological station observations of dust phenomena, dust transport model, and weather maps consistently show that the dust particles were transported from the source regions (Inner Mongolia, Man-Ju, and Ordos areas) to Korea via the northeastern part of China. Network observations of the PM(10) concentrations in Korea revealed that a majority of the heavy dust particles traveled across South Korea from the northwest to the southeast direction with a horizontal scale of 250-300km and a traveling speed of approximately 40kmh(-1). This extraordinary dust event, in terms of its intensity and timing during the year, occurred due to the blockage of an unusually intensified low-pressure system in the northeastern part of China as well as high-pressure system centered over the Sea of Okhotsk and the Kuril Islands. The low values of the particle depolarization ratio (delta(532)) (<or=0.05) and color ratio (CR) during the pre-dust period indicate the presence of spherical, non-dust, and relatively small particles. The mean delta(532) value was approximately 0.123+/-0.069 between altitudes of ground approximately 2.8km, and 0.161+/-0.049 for near-surface dust layer (ground approximately 1.2km). This value is quite similar to that obtained during the 3-year SNU-Lidar measurements in Seoul (delta(532) approximately 0.136+/-0.027). The value of delta(532) during the 2nd multilayered dust episode ranged between 0.081 and 0.120 for near-surface dust layers, and between 0.076 and 0.114 for elevated dust layers. The CALIPSO measurements of beta(532), delta(532), and CR also revealed the presence of dense dust aerosols along the transport route.

Meteorology and Atmospheric Physics, 2014

ABSTRACT This study performed a three-dimensional regional-scale simulation of aerosol and cloud ... more ABSTRACT This study performed a three-dimensional regional-scale simulation of aerosol and cloud fields using a meso-scale non-hydrostatic model with a bin-based cloud microphysics. The representation of aerosols in the model has been improved to account for more realistic multi-modal size distribution and multiple chemical compositions. Two case studies for shallow stratocumulus over Northeast Asia in March 2005 were conducted with different aerosol conditions to evaluate model performance. Improved condensation nuclei (CN) and cloud condensation nuclei (CCN) are attributable to the newly constructed aerosol size distribution. The simulated results of cloud microphysical properties (cloud droplet effective radius, liquid water path, and optical thickness) with improved CN/CCN number are close to the retrievals from satellite-based observation. The effects of aerosol on the microphysical properties of shallow stratocumulus are investigated by model simulation, in terms of columnar aerosol number concentration. Enhanced aerosol number concentration results in increased liquid water path in humid case, but invariant liquid water path in dry case primarily due to precipitation occurrence. The changes of cloud microphysical properties are more predominant for small aerosol burden than for large aerosol burden with the retarded changes in cloud mass and size due to inactive condensation and collision-coalescence processes. Quantitative evaluation of sensitivity factor between aerosol and cloud microphysical properties indicates a strong aerosol-cloud interaction in Northeast Asian region.

Journal of the Meteorological Society of Japan, 2008

An intercomparison study of ground-based Mie-scattering lidar systems was held at Gosan, Korea du... more An intercomparison study of ground-based Mie-scattering lidar systems was held at Gosan, Korea during ABC-EAREX 2005 in order to ensure the correctness and accuracy of the lidar retrieval algorithms as well as the aerosol extinction profiles. We compared the vertical profiles of the range-corrected raw lidar signals as well as the aerosol extinction coefficients determined from different types of Mie-scattering lidar systems. Three different aerosol loading cases were selected; in these cases, the mean deviations of the range-corrected raw lidar signals were estimated to be 4.5%, 8.0%, and 7.3%. An intercomparison of the instruments by an identical data-handling procedure (Fernald approach) demonstrated that the aerosol extinction profiles for the three selected cases were in agreement within a bias difference of 0.0051 km-1. The mean deviation of the signals for the aerosol layer between 0.6 and 3.0 km was 3.0%. The systems were intercompared for two lidar inversion algorithms by using simultaneous lidar measurement data sets as input; these input data sets showed agreement with their aerosol extinction profiles within a bias difference of 0.0086 km-1 and a mean deviation of 11.6%.

Journal of Geophysical Research, 2011

Vertical dust flux parameterizations were assessed by implementing three different dust emission ... more Vertical dust flux parameterizations were assessed by implementing three different dust emission schemes, namely, those of Marticorena and Bergametti (1995), Lu and Shao (1999), and Shao (2004) (hereinafter referred to as MB, LS, and S04 schemes, respectively) in Weather Research and Forecasting with Chemistry (WRF/Chem). Through sensitivity tests, the scattering of vertical dust fluxes resulting from different parameterizations was shown even under the condition of same horizontal sand flux. The difference between the estimated vertical dust fluxes of three emission schemes ranges from the order of 10 1 for sand to the order of 10 2 for clay. The MB scheme generally produces higher dust emissions than the LS and S04 schemes, and the difference is the greatest for clay because the MB scheme considers vertical dust flux to be related to clay content, while the LS and S04 schemes consider it to be inversely proportional to surface hardness. To investigate the performance of each dust emission scheme in the simulation of Asian dust events, a case study was carried out for a severe Asian dust event that took place between 30 March and 1 April 2007. Simulation results reproduced the outbreak and transport pattern of dust plumes satisfactorily. However, the estimated dust emission amounts in each scheme differed greatly, particularly in loamy soil. The total dust emission amounts averaged for the main dust source region in this Asian dust event for five consecutive days are 84 Tg, 149 Tg, and 532 Tg for the LS, S04, and MB schemes, respectively.

Journal of Geophysical Research, 2007

The characteristics of air masses arriving at Gosan, Korea, were investigated on the basis of PM ... more The characteristics of air masses arriving at Gosan, Korea, were investigated on the basis of PM 2.5 measurements during six intensive measurement periods (IMPs) in order to delineate the influences of various types of seasonal events in northeast Asia. The air masses arrived from the northwest/west along prevailing westerlies during three IMPs performed in the nonsummer seasons. Three characteristic periods of stagnation, Asian dust, and pollution periods were identified in November 2001, spring 2002, and February 2003, respectively. Another three characteristic periods of typhoon, biomass burning, and marine background periods were identified in the summer seasons: late August to early September 2002, June 2003, and August 2003, respectively. Anthropogenic pollution levels increased significantly not only because of stagnant meteorological conditions but also because of transport from high-emission areas with prevailing westerly winds during heating seasons (winter and/or fall). In spring, there was a good contrast between a weak Asian dust (AD) period with dusts transported from the Gobi desert and a strong AD period with dusts transported from Inner Mongolia. During the weak AD period the levels of anthropogenic pollutants were high, whereas during the strong AD period, anthropogenic ion concentrations were significantly low in spite of high mass concentrations. In summer, marine influences were strong either because of transport from the Pacific Ocean or the effects of typhoons. Influences from biomass burning from China and/or Russia were the strongest in June (biomass burning period) but continued in the marine background period.

Asia Pacific Journal of Atmospheric Sciences, Oct 1, 1988

Aeolian Research, 2011

The dust cycle is an integral part of the Earth system. Each year, an estimated 2000Mt dust is em... more The dust cycle is an integral part of the Earth system. Each year, an estimated 2000Mt dust is emitted into the atmosphere, 75% of which is deposited to the land and 25% to the ocean. The emitted and deposited dust participates in a range physical, chemical and bio-geological processes that interact with the cycles of energy, carbon and water. Dust

An unarmored dinoflagellate Cochlodinium polykrikoides has formed red tides responsible for fish ... more An unarmored dinoflagellate Cochlodinium polykrikoides has formed red tides responsible for fish mass mortalities especially in coastal areas of western Japan and southern Korea almost every summer to autumn. In laboratory culture, the optimum temperature for growth of the species is ca. 27 8C. Since the species cannot survive in water of temperatures of less than 10 8C, it was considered to over-winter in some certain regions as a motile form or resting cyst, and expand its distribution after the temperature increases to a level tolerable for growth. To determine the over-wintering regions and migration pattern of C. polykrikoides, occurrences of the motile cells were surveyed in the coastal and offshore areas of western Kyushu, Japan and south coast of the Korean Peninsula from April 2006 to August 2008. Cells of C. polykrikoides were found at 14 sites during the investigated period. Motile cells occurred throughout the year in Usuka Bay, Hirado of West Japan. From offshore regions of the Goto Islands and off Shin-Nagasaki Fishing Port, motile cells of C. polykrikoides were first detected from late May, and continuously occurred until February in Nama Bay of the Kami-Goto Islands. This first appearance was before red tides of C. polykrikoides reported at coastal areas in western Kyushu. In Korea, this species was first observed in May and disappeared after October in 2007. These occurrence patterns imply that Usuka Bay in Hirado is one of the over-wintering regions in western Kyushu, and also this species is possibly transported into the northern part of the East China Sea by the Tsushima Warm Current every year.

Journal of Korean Society for Atmospheric Environment

A case study was conducted for a severe wintertime dust event that occurred on December 29, 2007 ... more A case study was conducted for a severe wintertime dust event that occurred on December 29, 2007 in Korea. Three different dust emission schemes, namely, those of Marticorena and Bergametti (1995), Lu and Shao (1999), and Shao (2004) (hereinafter, referred to MB, LS, and S04 schemes, respectively) were implemented in Weather Research Forecast with Chemistry (WRF/Chem) to assess their performance in simulating wintertime Asian dust events. WRF/Chem simulation reproduces dust emission over Mongolia on December 27 and 28, 2007 and the onset timing of the dust event in Korea well. There is, however, a huge difference among the estimated dust emission amounts for the three schemes; the dust concentration derived by MB scheme is 6 times larger than that from LS scheme. The three schemes overestimate dust concentrations when comparing to observed surface-level PM 10 mass concentrations in Ganghwa, Seoul, and Yeongwol. This discrepancy is thought to be mainly due to the overestimated model winds and the surface condition such as snow cover fraction, which did not adequately represent the real conditions. Considering frozen soil effect on dust emission, the model results are comparable with observation data: it is important to consider frozen soil in simulating wintertime dust events.

Air Quality, Atmosphere & Health

Atmospheric Chemistry and Physics Discussions

A bin-based meso-scale cloud model has been employed to explore the aerosol influence on the clou... more A bin-based meso-scale cloud model has been employed to explore the aerosol influence on the cloud microphysical properties and precipitation efficiency of shallow stratocumulus in East Asia in March 2005. We newly constructed aerosol size distributions and hygroscopicity parameters for five aerosol species that reproduced observed

Proceedings of Spie the International Society For Optical Engineering, 2003

In order to investigate the characteristic of optical properties of Asian dust particles, the atm... more In order to investigate the characteristic of optical properties of Asian dust particles, the atmospheric aerosol vertical profile was measured with the multi-wavelength LIDAR system, at the Gosan super site (33 • 17 N, 126 • 10 E) in Jeju Island, Korea, during the ACE-Asia intensive observation period, 11 March-4 May 2001. An air mass backward trajectory analysis, using Hysplit-4, was carried out to track the aerosol plume, with high mass loading, from the Chinese desert regions during the period of Asian dust storm events. Vertical atmospheric aerosol profiles on three major Asian dust storm event days, 22 March and 13 and 26 April 2001, have been analyzed. The LIDAR-derived aerosol optical depth values were compared with those measured by a collocated sunphotometer.

Journal of Korean Society for Atmospheric Environment, 2007

Journal of Korean Society for Atmospheric Environment, 2013

Journal of Korean Society for Atmospheric Environment, 2010

Journal of Korean Society for Atmospheric Environment, 2012

Journal of Geophysical Research: Atmospheres, 2013

ABSTRACT The Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) aerosol optical depth (AOD... more ABSTRACT The Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) aerosol optical depth (AOD) has been compared with the Moderate Resolution Imaging Spectroradiometer (MODIS)-Aqua AOD using Level 2 products of both instruments. Such comparisons have been performed for five different aerosol subtypes classified by CALIOP algorithm, namely clean marine, dust, polluted dust, polluted continental, and biomass burning, over the ocean from June 2006 to December 2010.MODIS AOD at 550 nm(0.111 ± 0.079) for the collocated data pairs is about 63% higher than CALIOP AOD at 532nm (0.068 ± 0.073). For clean marine,MODIS AOD(0.110 ± 0.064) is almost twice the CALIOPAOD (0.056 ± 0.038), and the difference between the AOD values has a strong latitude dependence likely related to the surface wind speed over the ocean. The difference in AOD for dust (13%) is observed to be the lowest among the five aerosol types under consideration, but it shows a slight regional variation. The discrepancy of AOD for dust also shows strong dependency on the layer mean of the particulate depolarization ratio. CALIOP AOD is higher than MODIS AOD for both polluted dust and polluted continental by 15% and 29%, respectively, for most of the ocean. One of the possible reasons for the difference is the misclassification of clean marine (or marine + dust) as polluted dust and polluted continental in the CALIOP algorithm. For biomass burning, uncertainty in the layer base altitude is thought to be one of the main reasons for the lower value of CALIOP AOD.

Meteorology and Atmospheric Physics, 2014

ABSTRACT Under cloudy conditions at the Gosan Climate Observatory (GCO), Korea, we observed disti... more ABSTRACT Under cloudy conditions at the Gosan Climate Observatory (GCO), Korea, we observed distinct new particle formation and growth (NPF) events from simultaneous co-located measurements of aerosol and cloud profiles, cloud cover, shortwave radiation, and the number concentration and size distribution of aerosols. The high frequency of NPF was observed at GCO under decreased downwelling solar radiation caused by clouds. Although we observed about 15 and 40 % decreases in downwelling surface shortwave radiations, in the presence of thick mid-level (low-level) clouds, on January 28 and 30, 2012, respectively, distinct NPFs with a growth rate of 3.3 (3.9) nm h(-1) were observed. We examined a 4-year series (May 2008 to April 2012) of continuous measurements of the size distribution of aerosol numbers and visually observed cloud cover. We found that approximately 13 % (i.e., 35 days out of 280 days) of total NPF events were observed under cloud-free conditions (i.e., cloud cover of 0/10). About 20 % (i.e., 57 days out of 280 days) of total NPF events occurred under mostly overcast conditions (i.e., cloud cover of 9/10-10/10). Although NPF events occurring under cloudy conditions were also found elsewhere, the frequency of NPF occurring at GCO seems much higher. The average value of relative humidity for the strong-NPF event days is lower than that of the weak and non-NPF event days for all cloud categories. No significant difference in the condensation sink was found among strong-, weak-, and non-NPF days, but the condensation sink showed a slight decreasing tendency with increasing cloudiness. Further investigations on precursor gases and preexisting aerosols under cloudy conditions are needed.

Science of The Total Environment, 2010

In this study, we investigate the transport of dust particles, its vertical distribution, and the... more In this study, we investigate the transport of dust particles, its vertical distribution, and the associated meteorological conditions during an Asian dust event that was observed in Seoul, Korea on May 29-31, 2008. This study analyzes data from ground-based and space-borne 2-wavelength polarization lidars, particulate mass concentrations, and synoptic weather data. Surface meteorological station observations of dust phenomena, dust transport model, and weather maps consistently show that the dust particles were transported from the source regions (Inner Mongolia, Man-Ju, and Ordos areas) to Korea via the northeastern part of China. Network observations of the PM(10) concentrations in Korea revealed that a majority of the heavy dust particles traveled across South Korea from the northwest to the southeast direction with a horizontal scale of 250-300km and a traveling speed of approximately 40kmh(-1). This extraordinary dust event, in terms of its intensity and timing during the year, occurred due to the blockage of an unusually intensified low-pressure system in the northeastern part of China as well as high-pressure system centered over the Sea of Okhotsk and the Kuril Islands. The low values of the particle depolarization ratio (delta(532)) (<or=0.05) and color ratio (CR) during the pre-dust period indicate the presence of spherical, non-dust, and relatively small particles. The mean delta(532) value was approximately 0.123+/-0.069 between altitudes of ground approximately 2.8km, and 0.161+/-0.049 for near-surface dust layer (ground approximately 1.2km). This value is quite similar to that obtained during the 3-year SNU-Lidar measurements in Seoul (delta(532) approximately 0.136+/-0.027). The value of delta(532) during the 2nd multilayered dust episode ranged between 0.081 and 0.120 for near-surface dust layers, and between 0.076 and 0.114 for elevated dust layers. The CALIPSO measurements of beta(532), delta(532), and CR also revealed the presence of dense dust aerosols along the transport route.

Meteorology and Atmospheric Physics, 2014

ABSTRACT This study performed a three-dimensional regional-scale simulation of aerosol and cloud ... more ABSTRACT This study performed a three-dimensional regional-scale simulation of aerosol and cloud fields using a meso-scale non-hydrostatic model with a bin-based cloud microphysics. The representation of aerosols in the model has been improved to account for more realistic multi-modal size distribution and multiple chemical compositions. Two case studies for shallow stratocumulus over Northeast Asia in March 2005 were conducted with different aerosol conditions to evaluate model performance. Improved condensation nuclei (CN) and cloud condensation nuclei (CCN) are attributable to the newly constructed aerosol size distribution. The simulated results of cloud microphysical properties (cloud droplet effective radius, liquid water path, and optical thickness) with improved CN/CCN number are close to the retrievals from satellite-based observation. The effects of aerosol on the microphysical properties of shallow stratocumulus are investigated by model simulation, in terms of columnar aerosol number concentration. Enhanced aerosol number concentration results in increased liquid water path in humid case, but invariant liquid water path in dry case primarily due to precipitation occurrence. The changes of cloud microphysical properties are more predominant for small aerosol burden than for large aerosol burden with the retarded changes in cloud mass and size due to inactive condensation and collision-coalescence processes. Quantitative evaluation of sensitivity factor between aerosol and cloud microphysical properties indicates a strong aerosol-cloud interaction in Northeast Asian region.

Journal of the Meteorological Society of Japan, 2008

An intercomparison study of ground-based Mie-scattering lidar systems was held at Gosan, Korea du... more An intercomparison study of ground-based Mie-scattering lidar systems was held at Gosan, Korea during ABC-EAREX 2005 in order to ensure the correctness and accuracy of the lidar retrieval algorithms as well as the aerosol extinction profiles. We compared the vertical profiles of the range-corrected raw lidar signals as well as the aerosol extinction coefficients determined from different types of Mie-scattering lidar systems. Three different aerosol loading cases were selected; in these cases, the mean deviations of the range-corrected raw lidar signals were estimated to be 4.5%, 8.0%, and 7.3%. An intercomparison of the instruments by an identical data-handling procedure (Fernald approach) demonstrated that the aerosol extinction profiles for the three selected cases were in agreement within a bias difference of 0.0051 km-1. The mean deviation of the signals for the aerosol layer between 0.6 and 3.0 km was 3.0%. The systems were intercompared for two lidar inversion algorithms by using simultaneous lidar measurement data sets as input; these input data sets showed agreement with their aerosol extinction profiles within a bias difference of 0.0086 km-1 and a mean deviation of 11.6%.

Journal of Geophysical Research, 2011

Vertical dust flux parameterizations were assessed by implementing three different dust emission ... more Vertical dust flux parameterizations were assessed by implementing three different dust emission schemes, namely, those of Marticorena and Bergametti (1995), Lu and Shao (1999), and Shao (2004) (hereinafter referred to as MB, LS, and S04 schemes, respectively) in Weather Research and Forecasting with Chemistry (WRF/Chem). Through sensitivity tests, the scattering of vertical dust fluxes resulting from different parameterizations was shown even under the condition of same horizontal sand flux. The difference between the estimated vertical dust fluxes of three emission schemes ranges from the order of 10 1 for sand to the order of 10 2 for clay. The MB scheme generally produces higher dust emissions than the LS and S04 schemes, and the difference is the greatest for clay because the MB scheme considers vertical dust flux to be related to clay content, while the LS and S04 schemes consider it to be inversely proportional to surface hardness. To investigate the performance of each dust emission scheme in the simulation of Asian dust events, a case study was carried out for a severe Asian dust event that took place between 30 March and 1 April 2007. Simulation results reproduced the outbreak and transport pattern of dust plumes satisfactorily. However, the estimated dust emission amounts in each scheme differed greatly, particularly in loamy soil. The total dust emission amounts averaged for the main dust source region in this Asian dust event for five consecutive days are 84 Tg, 149 Tg, and 532 Tg for the LS, S04, and MB schemes, respectively.

Journal of Geophysical Research, 2007

The characteristics of air masses arriving at Gosan, Korea, were investigated on the basis of PM ... more The characteristics of air masses arriving at Gosan, Korea, were investigated on the basis of PM 2.5 measurements during six intensive measurement periods (IMPs) in order to delineate the influences of various types of seasonal events in northeast Asia. The air masses arrived from the northwest/west along prevailing westerlies during three IMPs performed in the nonsummer seasons. Three characteristic periods of stagnation, Asian dust, and pollution periods were identified in November 2001, spring 2002, and February 2003, respectively. Another three characteristic periods of typhoon, biomass burning, and marine background periods were identified in the summer seasons: late August to early September 2002, June 2003, and August 2003, respectively. Anthropogenic pollution levels increased significantly not only because of stagnant meteorological conditions but also because of transport from high-emission areas with prevailing westerly winds during heating seasons (winter and/or fall). In spring, there was a good contrast between a weak Asian dust (AD) period with dusts transported from the Gobi desert and a strong AD period with dusts transported from Inner Mongolia. During the weak AD period the levels of anthropogenic pollutants were high, whereas during the strong AD period, anthropogenic ion concentrations were significantly low in spite of high mass concentrations. In summer, marine influences were strong either because of transport from the Pacific Ocean or the effects of typhoons. Influences from biomass burning from China and/or Russia were the strongest in June (biomass burning period) but continued in the marine background period.