[A-AS10] 成層圏・対流圏過程とその気候への影響

[AAS10-P05] Impact of unmitigated HFC emissions on stratospheric ozone at the end of the 21st century as simulated by chemistry-climate model

*秋吉 英治¹、デュプュイ エリック、山下 陽介^1,2 (1.国立環境研究所、2.海洋研究開発機構)

キーワード：HFC、オゾン、気温、化学気候モデル、アンサンブル実験、統計的有意性

Hydrouorocarbons (HFCs) have been increasingly replacing chlorouorocarbons and hydrochlorouorocarbons. Although their ozone-depleting potential is negligible, they modify atmospheric temperature and circulation patterns as greenhouse gases, thereby indirectly influencing stratospheric ozone recovery. In this study, we present multi-member ensemble simulations designed to estimate the impact of HFCs on stratospheric temperature, ozone and circulation changes at the end of the century. We compared simulations with and without HFCs for two three-dimensional chemistry climate models that use the same chemistry module but different physical schemes. At low and mid-latitudes, temperature and ozone responses were comparable for both models and in general agreement with previous 2-D model studies. HFCs induced a marked temperature increase up to about 10−20 hPa and vertically alternating positive and negative ozone anomalies. We explained this pattern by competing effects of vertical motion (low and middle stratosphere) and temperature (upper stratosphere) anomalies. At northern high latitudes, there were strong discrepancies with previous studies and between the models themselves, attributed to differences in ozone anomalies caused by wave activity during winter. Quantitatively, we found a net positive, but small, HFC impact on total ozone amounts. Largest anomalies were less than 1% in the winter polar stratosphere. Our results indicate that increasing HFC amounts will likely have a limited impact on stratospheric ozone recovery within this century, with large uncertainty in the polar regions.