抄録
Filter sampling was conducted at the summit of Mt. Fuji to observe microphysical properties of Asian dust in the free troposphere. In order to avoid influence of local mineral dust elevated from near the summit, the filter sampling was conducted only during the nighttime from 0:00 to 6:00. Volume-size distribution of water-insoluble aerosol particles was measured by using a Coulter Multisizer. The samples with the minimum local influence showed the size distributions with the mode diameters of 3.1 and 4.5 μm. These mode diameters correspond to those measured on the ground during Asian dust event. Therefore, the measured water-insoluble aerosol particles were of background Asian dust in the free troposphere. In addition, a narrow size distribution with a mode diameter of 1.8 μm which could be the contribution of inorganic ash spheres also appeared. The measurement of sample which was separated by wind direction and speed during 2006 summer showed the mode diameter of around 5-6 μm, which would be of the mineral dust elevated from near the summit. For proper observation of mineral dust (water-insoluble particle) in the free troposphere, it is required to adopt the sampling time from 0:00 till sunrise.
