The aerosol number concentration have measured with an aerodynamic particle sizer spectrometer(APS) at Gosan in Jeju Island, which is known as background area in Korea, from March 2010 to February 2011. The obtained results of asian dust events and non-asian dust period have been compared. The results show that the entire averaged aerosol number concentration from APS measurement during asian dust events and non-asian dust period are about 341 particles/㎝3 and 240 particles/㎝3, respectively. During asian dust events, the number concentration in small size ranges(≤0.4 ㎛) are similar to non-asian dust period, however, those in large size ranges(≥0.7 ㎛) are very higher than non-asian dust period. The contributions of the size resolved number concentration(23 channel in 0.25∼10.0 ㎛) to total number concentration in that range are dramatically decreased with increased particle size. The contributions of smaller size ranges(≤0.4 ㎛) during asian dust events are very low compared with non-asian dust period, on the other hand, those of larger size ranges(≥0.4 ㎛) are higher than non-asian dust period. total aerosol number concentration are depended on the number concentration in range of smaller than 0.58 ㎛ during non-asian dust period and asian dust events. On the other hand, PM10 mass concentration has mainly affected with the number concentration in range of smaller than 1.0 ㎛ during non-asian dust period, however, during asian dust events, the mass concentration has mainly affected with the number concentration in range of 0.65∼3.0 ㎛.

The aerosol number concentration have measured with an aerodynamic particle sizer spectrometer(APS) at Gosan site, which is known as background area in Korea, from January to September 2011. The temporal variation and the size distribution of aerosol number concentration have been investigated. The entire averaged aerosol number concentration in the size range 0.25∼32.0 ㎛ is about 252 particles/㎝3. The number concentration in small size ranges(≤ 0.5 ㎛) are very higher than those in large size ranges, such as, the number concentration in range of larger than 6.5 ㎛ are almost zero particles/㎝3. The contributions of the number concentration to PM10 and/or PM2.5 are about 34%, 20.1% and 20.4% in the size range 0.25∼0.28 ㎛, 0.28∼0.30 ㎛ and 0.30∼0.35 ㎛, respectively, however, the contributions are below 1% in range of larger than 0.58 ㎛. The monthly variations in the number concentration in smaller size range(<1.0 ㎛) are evidently different from the variations in range of larger than 1.0 ㎛, but the variations are appeared similar patterns in smaller size range(<1.0 ㎛), also the variations in range of larger than 1.0 ㎛ are similar too. The diurnal variations in the number concentration for smaller particle(<1.0 ㎛) are not much, but the variations for larger particle are very evident. Size-fractioned aerosol number concentrations are dramatically decreased with increased particle size. The monthly differences in the size-fractioned number concentrations for smaller size range(<0.7 ㎛) are not observed, however, the remarkable monthly differences are observed for larger size than 0.7 ㎛.

The aerosol number concentration have measured with an aerodynamic particle sizer spectrometer(APS) at Gosan site in Jeju, Korea, from March 2010 to March 2011. And then the atmospheric aerosol number concentration, the temporal variation and the size distribution of aerosol number concentration have been investigated. The aerosol number concentration varies significantly from 748 particles/㎝3 to zero particles/㎝3. The average number concentration in small size ranges are very higher than those in large size ranges. The number concentrations in the size range 0.25∼0.28 ㎛, 0.40∼0.45 ㎛ and 2.0∼2.5 ㎛ are about 84 particles/㎝3, 2 particles/㎝3 and 0.4 particles/㎝3, respectively. The number concentrations in range of larger than 7.5 ㎛ are below 0.001 particles/㎝3. The seasonal variations in the number concentration for smaller particle(<1.0 ㎛) are not much, but the variations for larger particle are very evident. And strong amplitudes of diurnal variations of entire averaged aerosol number concentration are not observed. Size-fractioned aerosol number concentrations are dramatically decreased with increased particle size. The size-fractioned aerosol number concentrations in size range 0.8∼4.0 ㎛ during nighttime are evidently higher than during daytime, but similar levels are appeared in other size range. The seasonal differences in the size-fractioned number concentrations for smaller size range(<0.7 ㎛) are not observed, however, the remarkable seasonal differences are observed for larger size than 0.7 ㎛.

To examine the fluctuations of aerosol number concentration with different size in the boundary layer of marine area during summer season, aerosol particles were assayed in the Ieodo Ocean Research Station, which is located 419 km southwest of Marado, the southernmost island of Korea, from 24 June to 4 July, 2008. The Laser Particle Counter (LPC) was used to measure the size of aerosol particles and NCEP/NCAR reanalysis data and sounding data were used to analyze the synoptic condition. The distribution of aerosol number concentration had a large variation from bigger particles more than 3 μm in diameter to smaller particles more than 1 μm in diameter with wind direction during precipitation. The aerosol number concentration decreased with increasing temperature. An increase (decrease) of small size of aerosol (0.3∼0.5 μm in diameter) number concentration was induced by convergence (divergence) of the wind fields. The aerosol number concentration of bigger size more than 3 μm in diameter after precipitation was removed as much as 89∼94% compared with aerosol number concentration before precipitation. It is considered that the larger aerosol particles would be more efficient for scavenging at marine boundary layer. In addition, the aerosol number concentration with divergence and convergence could be related with the occurrence and mechanism of aerosol in marine boundary layer.

To understand the development mechanism of the aerosols in the surface boundary layer, the variation in the aerosol number concentration due to the divergence and convergence of the wind fields was investigated. The aerosol number concentration was measured in the size ranges of 0.3∼10.0 ㎛ using a laser particle counter(LPC) from 0000 LST on 03 Feb. to 0600 LST on 07 Feb. 2004 at Mokpo in Korea during snowfall. The Velocity Azimuth Display(VAD) technique was used to retrieve the radar wind fields such as the horizontal wind field, divergence, and deformations including the vertical air velocity from a single Doppler radar. As a result, the distribution of the aerosol number concentration is apparently different for particles larger than 1 ㎛ during snowfall, and it has a tendency to increase at the beginning of the snowfall. The increase and decrease in the aerosol concentration due to the convergence and divergence of the wind fields corresponded to the particles with diameters greater than 1 ㎛. It is found that the fluctuations in the aerosol number concentration are well correlated with the development and dissipation of snowfall radar echoes due to the convergence and divergence of horizontal wind fields near the surface boundary layer in the inland during the snowfall.

The characteristics for the aerosol number distribution was studied during spring, 2004 in Incheon. Optical Particle Counter (OPC, HIAC/ROYCO 5230) was used in order to measure the number concentration of aerosol in the range of 0.3～25㎛. The obtained results were compared with PM2.5 and PM10 data during Asian dust events. The results show that the size resolved aerosol number concentration from OPC measurement has a similar tendency with PM10 and PM2.5 mass concentration. During Asian dust periods, the number concentrations in large particle (CH5～CH8) increase more than small particles which diameter is less than 2.23㎛(CH5) and the same results were shown when PM10 was compared with PM2.5 data compared with non-dust days, Consequently, this study shows that size resolved aerosol number concentration from OPC measurement can be used as a useful tool in comparison of mass concentration data.