3:45 PM - 4:00 PM
[AAS21-03] Measurements of the hygroscopicity and wet removal of black-carbon-containing particles in Tokyo
Keywords:black carbon, hygroscopicity, wet removal
Throughout the observation period, for BC-containing particles with a dry diameter of about 200 nm, the particles with smaller BC fractions tended to represent greater water uptake, and the number fraction of the less hygroscopic (Growth factor < 1.2 at 85% relative humidity) BC-containing particles was more than 70% of the total BC-containing particles. The measured average number size distribution of BC cores in rainwater was larger than that in the surface air before precipitation began, and the dependence of the wet removal of BC-containing particles on their BC-core sizes was successfully explained by the measured microphysical properties of BC-containing particles in the air and an assumed maximum supersaturation that the particles would have experienced during rain events. These measurement data indicated that BC-containing particles in Tokyo, especially particles with small BC cores (or with high critical supersaturation), were efficiently transported upward without being removed by precipitation.