[A-AS06] 成層圏・対流圏過程とその気候への影響

[AAS06-P04] 再解析データにおける大規模火山噴火にともなうブリューワー・ドブソン循環の応答

*藤原 正智¹、Abalos Marta²、Martineau Patrick³、Wright Jonathon⁴ (1.北海道大学 大学院地球環境科学研究院、2.マドリード・コンプルテンセ大学、3.海洋研究開発機構、4.精華大学)

キーワード：ブリューワ―・ドブソン循環、火山噴火

The responses of the Brewer-Dobson circulation (BDC, i.e., the residual mean circulation) to the eruptions of Mt. Agung in March 1963, El Chichón in April 1982, and Mt. Pinatubo in June 1991 are investigated using global atmospheric reanalysis datasets, JRA-55, MERRA-2, and ERA-Interim. Multiple linear regression is applied to the zonal and monthly mean time series of temperature, zonal wind, BDC stream function, Eiassen-Palm flux divergence, and other variables/terms for two periods, 1980–2010 (for the three datasets) and 1958–2001 (for JRA-55 only), by considering explanatory factors of seasonal harmonics, linear trends, Quasi-Biennial Oscillation, solar cycle, and El Niño Southern Oscillation. The residuals are used to define the volcanic signals for the three eruptions separately.

Analysis using JRA-55 data showed the following: (1) in the first DJF season after each eruption, the Northern-Hemisphere BDC cell was weakened after Mt. Pinatubo and Mt. Agung eruptions, but was strengthened after El Chichón eruption; (2) in the second-year JJA, the Southern-Hemisphere BDC cell was weakened after El Chichón and Mt. Agung eruptions, but was strengthened after Mt. Pinatubo eruption. MERRA-2 and ERA-Interim showed qualitatively the same results for Mt. Pinatubo and El Chichón eruptions as JRA-55. Thus, the BDC response was different for different eruptions and for different seasons. The EPFD response (anomaly) was found to correspond to the BDC (v_bar_star) response (anomaly) for all the cases. Interpretation of these results will be discussed at the meeting.