大気中の酸化力の短期的な変動
Martin R Manning1, David C Lowe, Rowena C Moss
1IPCC Working Group I Support Unit, Boulder, Colorado 80305, USA. Martin.Manning@noaa.gov
Nature
|August 19, 2005
まとめ
大気中のヒドロキシルラジカル (OH) の濃度は長期的な傾向を示さないが,短期的な変動を示している. 放射性炭素による測定は,月々の変化を明らかにし,大規模な火山噴火や火災の後に著しく減少しています.
科学分野:
- 大気化学 大気化学
- 気候科学 気候科学
- 環境監視 環境モニタリング
背景:
- ヒドロキシル基 (OH) は大気中の主要な酸化物質であり,微量ガス除去と大気中の"浄化"能力の調節に不可欠である.
- OH濃度の傾向と変動性を理解することは,大気の自己浄化過程の変化を評価するために不可欠です.
- 短期的な (年間から月間) OHの変動を定量化することは,大気科学における大きな課題となっています.
研究 の 目的:
- ハイドロキシルラジカル濃度の短期的変動と長期的傾向を定量化するために.
- 大気中のOH濃度の診断ツールとして放射性炭素測定を用いる.
- 火山噴火や野火などの大きな出来事がOHレベルに与える影響を調査する.
主な方法:
- ニュージーランドと南極のクリーンエアサイトから放射性炭素 (14CO) を含む一酸化炭素の13年間の記録の分析.
- 14CO生産における既知の変動を補正するためにモデル研究を適用する.
- 14COをプロキシとして用いて,ヒドロキシル基の濃度における短期的な変化を診断する.
主要な成果:
- 13年間の研究期間中,ヒドロキシルラジカル濃度の長期的な有意な傾向は検出されなかった.
- OH濃度の短期的な変動 (約10%) が繰り返し,数ヶ月間持続することが確認された.
- 1991年のマウント・マットと関連したOH濃度の大幅な減少 (最大20%まで) が観察されました. ピナトゥボ噴火と1997年のインドネシアの火災.
結論:
- ハイドロキシルラジカル濃度は短期的に有意な変動を示しているが,このデータセットに基づいて見分けられる長期的な傾向はない.
- 大規模な火山噴火や広範囲の野火などの主要な大気現象は,OH濃度を一時的に低下させる可能性があります.
- 放射性炭素測定は,短期的な大気中の酸化物質の動態を監視するための貴重なツールです.
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