5:15 PM - 6:45 PM
[AAS09-P13] Characterization and long-term trend analysis of aerosols in Japan with a focus on Asian dust
Keywords:yellow sand, Aerosol optical thickness, natural origin, artificial origin
The Asian dust, known to cause health hazards and visibility deterioration, presents challenges in understanding its frequency and transport long-term trends and even their signs. This study undertook long-term aerosol observations at the SKYNET/Chiba site, Japan, utilizing sky radiometers and Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS). Analysis of the most recent Asian dust event in April 2023, as reported by the Japan Meteorological Agency (JMA), revealed a low Ångström Exponent below 0.5 and an absorption aerosol optical thickness of 0.05-0.07 in the UV region, strongly indicating the arrival of Asian dust in Chiba. However, there were no significant differences in aerosol optical thickness (AOT) or aerosol extinction coefficient at 0-1 km compared to other days. Simultaneous measurements of PM2.5 mass concentrations did not reach levels that would restrict outdoor activities. These findings suggest that the amount of Asian dust during this event did not markedly impact human activities in Chiba. Furthermore, black carbon mass concentrations showed no significant increase compared to non-dust days, suggesting limited influence of anthropogenic aerosols in this air mass. To distinguish between anthropogenic fine particle aerosols and naturally occurring coarse particle aerosols, the sky radiometer AOT was divided into fAOT and cAOT, respectively, and their long-term trend analysis was conducted for the period 2006-2023. A long-term decreasing trend of about 4% per year was observed for fAOT, while cAOT exhibited no significant change. This study also aims to present similar trend analyses conducted at other SKYNET sites besides Chiba.