[M-AG33] 原爆による「黒い雨」領域の推定に関する基礎的研究

[MAG33-P09] 超微細粒子および大気イオンの観測に基づく能登半島における新粒子生成過程の解明

*小松 正基¹、久保田 誠史²、表野 宏之²、岩本 洋子³、Alessia Nicosia⁴、岩田 歩⁵、加藤 俊吾⁶、定永 靖宗⁷、兼保 直樹^8,9、松木 篤¹⁰ (1.金沢大学地球社会基盤学類、2.金沢大学院自然科学研究科、3.広島大学大学院総合生命科学研究科、4.CNR-ISAC、5.気象庁 気象研究所 気象予報研究部 第五研究室、6.東京都立大学　都市環境学部　環境応用化学科、7.大阪公立大学大学院工学研究科応用化学分野、8.福島国際研究教育機構、9.産業技術総合研究所環境管理技術研究部門、10.金沢大学環日本海域環境研究センター)

キーワード：新粒子生成、クラスターイオン、イオン誘発核生成、空間線量

The particles generated by new particle formation (NPF) ultimately determine the concentration of cloud condensation nuclei (CCN), thereby influence the Earth's climate. The mechanism of NPF is largely driven by regional environmental factors, and its detailed understanding requires the direct observation of ultrafine particles as well as air ions. In this study, we newly introduced NAIS (Neutral cluster and Air Ion Spectrometer, Airel, Estonia) to observe the size distribution of newly formed particles and air ions at NOTOGRO (Noto ground-based Research Observatory: 37.45N, 137.36E), along the western-coast of mainland Japan. We identified in total 46 NPF events during the observation period from 18 May 2023 to 30 November 2023. Most events were predominantly daytime events most likely involving photochemical oxidation. The highest event frequency occurred in May when solar radiation and associated H₂SO₄ proxy were the highest. Throughout the observation period, NPF events were accompanied by an increase in ion concentrations. However, the contribution of ions to daytime NPF in Noto was found to be minimal, suggesting that the neutral clustering being the dominant pathway. It must be noted that few nighttime NPF events were also observed in Noto in late autumn. However, the nighttime events observed in this study did not involve in-situ formation and growth of ultrafine and ions, suggesting transport of previously formed particles from upwind. Our findings suggested the possibility of ion-induced nucleation occurring over the Sea of Japan accompanied by the inflow of clean air masses from the free troposphere after the passage of a cold front.