日本地球惑星科学連合2019年大会

講演情報

[J] ポスター発表

セッション記号 A (大気水圏科学) » A-AS 大気科学・気象学・大気環境

[A-AS05] 成層圏・対流圏過程とその気候への影響

2019年5月29日(水) 17:15 〜 18:30 ポスター会場 (幕張メッセ国際展示場 8ホール)

コンビーナ:河谷 芳雄(国立研究開発法人海洋研究開発機構)、渡辺 真吾(国立研究開発法人海洋研究開発機構)、関谷 高志(国立研究開発法人 海洋研究開発機構)、佐藤 薫(東京大学 大学院理学系研究科 地球惑星科学専攻)

[AAS05-P07] Selection bias of quasi-fixed-point observations in the ExUTLS and its impact on the seasonal record

*稲飯 洋一1町田 敏暢2松枝 秀和3澤 庸介3坪井 一寛3勝又 啓一2,4森本 真司1青木 周司1中澤 高清1藤田 遼5,1 (1.東北大学、2.環境研、3.気象研、4.高千穂化学工業、5.Imperial College London)

キーワード:地球大気、観測

Fixed-point observations are essential for long-term monitoring of the atmospheric environment. However, some attention might be paid to the interpretation of seasonal variations appearing in the observational record, particularly for regions with large seasonal variations. In the extra-tropical upper troposphere/lower stratosphere (ExUTLS), the climatological tropopause height changes with season. This leads to a seasonal dependence of whether individual fixed-point observations are included in the stratosphere or the troposphere. In this study, using the reanalysis fields, quasi-fixed-point observations in the ExUTLS are simulated and categorized as being in the troposphere or stratosphere based on their position relative to the dynamic tropopause, to investigate seasonal tendencies of the categorization. The influence of these tendencies on seasonal variations of atmospheric composition in the categorized data is estimated. The seasonal cycles of CH4, N2O and SF6 mixing ratios are found to change with the categorization method. In particular, the minimum values for these tropospheric tracers in observations categorized as stratospheric occur 1–2 months later than in uncategorized observations. This delay in stratospheric record is interpreted as the selection bias, that is, the air mass categorized as the stratospheric atmosphere biased to some specific meteorological situation due to the seasonal variation of ExUTLS meteorological field.