Amount and State of Mineral Particles in the Upper Mixed Layer and the Lower Free Troposphere over Mt. Raizan, Southwestern Japan: Unmanned Airplane Measurements in the Spring of 2003

Abstract

In-situ observations and sampling of aerosol particles from 800 to 2000 m altitude, the upper mixed layer and lowermost free troposphere, were carried out over Mt. Raizan (Fukuoka, Japan) in the spring of 2003 using an optical particle counter and a cascade impactor borne in an unmanned radio-controlled airplane. In the mixed layer, mineral particles, sea salt particles, as well as the mixture of the two were dominant among the coarse particles, whereas sulfate particles dominated the fine particles. In the free troposphere, mineral particles dominated both the coarse and fine particles.The volume concentrations of particles including mineral constituents were derived using the number concentration and the composition of aerosol particles. The volume concentrations of particles including mineral constituents in the mixed layer and free troposphere were estimated to be 9.7 × 10−6−7.7 × 10−5 cm3 m−3 and 1.4 × 10−6−5.2 × 10−6 cm3 m−3, respectively.The number fractions of mineral particles mixed with sea salt of all the mineral particles in the mixed layer were much higher than those in the free troposphere. These results suggest that mineral particles mixed with sea salt were formed in the marine boundary layer. The weather record suggests that the formation process through the clouds, which has previously been considered an eflicient formation process for mixed particles, cannot explain sufficiently the observed abundance of mineral particles internally mixed with sea salt.