Woon-Seon Jung

Estimates of Aerosol Indirect Effect from Terra MODIS over Republic of Korea

Moderate resolution imaging spectroradiometer (MODIS) data have been analyzed over four different regions (Yellow sea, Korean inland, East Sea, and South Sea) in Republic of Korea to investigate the seasonal variability of aerosol-cloud properties and aerosol indirect effect during the past decade (2000–2009). Aerosol optical depth (AOD) was found to be consistently high during spring. Cloud ice radius (CIR) also showed higher values during spring, while an enhancement in cloud water radius (CWR) and fine mode fraction (FMF) was observed during summer. AOD and aerosol index (AI) were found to be higher during January to June. However, FMF and CWR showed enhancement during July to December. Aerosol indirect effect (AIE) in each year has been estimated and found to be showing positive and negative indirect effects. The AIE for fixed cloud ice path (CIP) showed positive indirect effect (Twomey effect) over Yellow sea, while the AIE for fixed cloud water path (CWP) showed a major negative indirect effect (anti-Twomey effect) over all regions. During Changma (summer monsoon) period, the AIE for both CIP and CWP showed dominant anti-Twomey effect in middle and low level clouds, indicating the growth of cloud droplet radius with changes in aerosols, enhancing the precipitation.

Characterization of Aerosol Concentration during Severe Asian Dust Period at Busan, Korea in 20 March 2010

Asian dust (or yellow sand) occurring mainly in spring in East Asia is affected by the distribution of weather systems. This study was performed to investigate the characteristics of suspended particulate for Asian dust at Busan, Korea in 20 March 2010, which was one of the extreme case for the last 10 years. There was used the data of weather chart, satellite, automatic weather system (AWS), PM10, laser particle counter (LPC), and backward trajectories model. In synoptically, the high pressure was located in the northwestern part and low pressure was located in the northeastern part of Korea. The strong westerly winds from surface to upper layer makes it possible to move air masses rapidly. Air masses passing through Gobi Desert in Mongolia and Inner Mongolia plateau covered the entire Korean peninsula. As the results of aerosol analysis, PM10 concentration at Gudeok mountain in Busan was recorded 2,344 μg/m in 2300 LST 20 March 2010 and their concentration was markedly increased at coarse mode particle. In surface condition, westerly wind about 3 ∼ 5 m/s was dominant and small particles of 0.3 ∼ 0.5 μm were distributed on the whole. In heavy metal components analysis, the elements from the land was predominated.

The Fluctuation of Marine Aerosol Number Concentrations Related with Vertical Winds

To investigate the fluctuation of marine aerosol number concentration at each different size with vertical winds in ocean area, aerosol particles and vertical wind components were measured in the Ieodo Ocean Research Station, which is located to 419 km southwest of Marado, the southernmost island of Korea, from 8 to 22 June 2009. The Laser Particle Counter (LPC) and ultrasonic anemometer were used to measure the number of aerosol particles and vertical wind speed. Surface weather chart, NCEP/NCAR reanalysis data and sounding data were used to analyze the synoptic condition. The distribution of aerosol number concentration had a large fluctuation of bigger particles more than 1.0 in diameter by vertical wind speed during precipitation. The aerosol particles larger than 1.0 in diameter increased as the wind changed from downward to upward during precipitation. The aerosol number concentration of bigger size than 1.0 in diameter increased about 5 times when vertical velocity was about 0.4 . In addition, the accumulation and coarse mode aerosol number concentration decreased about 45% and 92%, respectively compared to concentrations during precipitation period. It is considered that vertical wind plays an important role for the increasing of coarse mode aerosol number concentration compared to the large aerosol particles sufficiently removed by the scavenging effect of horizontal winds. Therefore, the upward vertical winds highly contribute to the formation and increase in aerosol number concentration below oceanic boundary layer.

Characterization of Chemical Properties of Precipitation at Busan, Korea, 2009

Abstract The seasonal variation of pH and ion components in precipitation were investigated from January to December 2009 at Busan, Korea. The precipitation was acidic with a volume-weighted mean pH concentration of 5.32, which ranged from 3.79 to 8.66. The volume-weighted mean conductivity showed 86.77 μS/cm and indicated higher concentration about 96.69 μS/cm in summer. The volume-weighted mean equivalent concentration of components followed the order: K + > Ca 2+ > nss-Ca 2+ > NH 4+ > Mg 2+ > Na + > Li + in cations and Cl - > SO 42- > nss-SO 42- > NO 3- > NO 2- > F - > Br - in anions. Particularly, concentration of K + and Cl - showed 56 and 78 % in cations and anions. The higher concentration in K + , Na + , Mg 2+ and Cl - were shown in Busan city as compared to the other cities. The neutralization factors have been found to have higher value for potassium ion in winter compared with different seasons, indicating significant neutralization of acidic components over the region by potassium. Therefore, the precipitation characteristics at Busan had both continental and coastal as consequence of pH, conductivity and ionic analyses.

Chemical Properties of Precipitation in Related to Wind Direction in Busan, Korea, 2009

The variation of acidity, conductivity, and ion components in precipitation depending on the dominant wind direction was investigated from January, 2009 to December 2009 in Busan, Korea. Both southwesterly and northeasterly winds were dominant in Busan area. The volume-weighted mean acidity showed pH 7, and the high conductivity indicated 200 µ sc m �1 in westerly wind. The volume-weighted mean equivalent concentration showed higher value of K +

The Distribution of Aerosol Concentration during the Asian Dust Period over Busan Area, Korea in Spring 2009

This study investigates the distribution of suspended particulates during the Asian dust period in Busan, Korea in the spring of 2009. Weather map and automatic weather system (AWS) data were used to analyze the synoptic weather conditions during the period. Particulate matter 10, laser particle counter data , satellite images and a backward trajectories model were used to analyze the aerosol particles distribution and their origins. In Case 1 (20 February 2009), when the PM10 concentration increased, the aerosol volume distribution of small (0.3-1.0 μm) particles decreased, while the concentration of large (1.0-10.0 μm) particles increased. When the PM10 concentration decreased, the aerosol volume distribution was observed to decrease as well. The prevailing winds changed from weak northerly winds to strong southwesterly winds when the concentration of the large particles increased. The correlation coefficient between the PM10 concentration and aerosol volume distribution of large particles showed a high positive value of over 0.9. The results from the trajectory model show that the Asian dust originated in the Gobi desert and the Nei Mongol plateau. In Case 2 (25 April 2009), when the PM10 concentration increased, the aerosol volume concentration of small (0.3-0.5 μm) particles decreased, but the concentration of large (0.5-10.0 μm) particles increased. The opposite was observed when the PM10 concentration decreased. The prevailing winds changed from northeasterly winds to southwesterly and northeasterly winds. The correlation coefficient between the PM10 concentration and aerosol volume distribution of large particles (1.0-10.0 μm) showed a high positive value of about 0.9. The results from the trajectory model show that the Asian dust originated in Manchuria and the eastern coast of China.