[A-CG54] Promotion of climate and earth system sciences using manned/unmanned aircrafts

[ACG54-03] Aircraft-based observation of mineral dust and ice-nucleating particles over the western North Pacific in summer

*Sho Ohata¹, Nobuhiro Moteki², Yutaka Tobo^3,4, Kouji Adachi⁵, Hitoshi MATSUI¹, Kazuyuki Kita⁶, Tatsuhiro Mori⁷, Makoto Koike⁸ (1.Nagoya University, 2.Tokyo Metropolitan University, 3.National Institute of Polar Research, 4.SOKENDAI, 5.Meteorological Research Institute, 6.Ibaraki University, 7.Keio University, 8.The University of Tokyo)

Keywords:Mineral dust, Ice nucleating particle, Aircraft observation

Mineral dust particles are recognized as a major type of ice-nucleating particles (INPs) in the atmosphere and thus can affect the optical properties and lifetime of clouds by inducing ice formation in the clouds. However, direct observations of the abundance of dust particles and INPs in the free troposphere are limited, hampering our understanding of the role of dust particles as INPs at altitudes relevant for mixed-phase clouds. In this study, aerosols were collected on filters using aircraft over the western North Pacific at altitudes of 0.2–8 km during the summer of 2022. Individual water-insoluble particles dispersed in water were analyzed using an optical technique (complex amplitude sensor, CAS) to quantify the number concentrations of dust particles (N_dust). The remaining aerosol samples were also analyzed using a cold-stage-based freezing technique (Cryogenic Refrigerator Applied to Freezing Test, CRAFT) to quantify the number concentrations of immersion-mode INPs (N_INP) in the temperature range of –30℃ to 0℃. During the eight observation flights, the N_dust was 1.2 ± 1.0 cm^–3 (mean ± 1σ) in the diameter range of 0.3–2.5 um, and the N_INP at –20℃ was 0.20 ± 0.19 L^–1 (mean ± 1σ). The mean N_dust value was 2 to 3 orders of magnitude lower than previously reported values near the major dust sources in East Asia, and the mean N_INP value was much lower than the annual mean value previously measured in the urban atmosphere of Tokyo. In this presentation, we show the variations of N_dust and N_INP during the observation period and discuss their possible relationships.