| Outline of Final Research Achievements |
Halogen radicals reduce ozone (O3) content in the troposphere through catalytic destruction. Tropospheric O3 content is important for the radiative balance of the Earth and is therefore important for global warming. Iodine radicals are of particular interest because of their rapid reaction with various chemical species including O3. However, because of low concentrations of iodine in the troposphere means, the quantification of iodine and iodine compounds is difficult.
Shipborne MAX-DOAS, a remote sensing technique was used on dedicated ocean cruises from the Arctic to the Southern Hemisphere to investigate variation of iodine monoxide (IO), an iodine radical, over the global remote ocean. Clear latitudinal variations were found: IO was not detected at high latitudes. However, it was detected at low latitudes and was particularly high over the tropical western Pacific, appearing as an iodine “fountain”, where an SST maximum, O3 minimum have been observed.
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| Academic Significance and Societal Importance of the Research Achievements |
成層圏のオゾン層破壊は、人間活動により放出されたハロゲン物質による連鎖的な光化学反応に因ることが知られている。地表付近 (大気境界層) においても、ハロゲン (臭素Br, 塩素Cl, ヨウ素I など) を含む化学種は反応性が極めて高く、様々な大気化学反応に関与し、また連鎖的にオゾンを壊すため重要である。しかし地球で7割を占める海洋上の大気中のハロゲンの動態は、観測が十分なされておらず明らかになっていない。本研究では海洋上のハロゲン物質の動態を地球規模で明らかにすることを一つの研究目的とした。その中で一酸化ヨウ素濃度の導出を行い、特に熱帯西部太平洋で高いという知見を得た。
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