[A-AS09] 成層圏・対流圏過程とその気候への影響

[AAS09-P05] Teleconnections of the quasi-biennial oscillation in multi-model QBOi-ENSO simulations

*直江 寛明¹、田口 正和²、Federico Serva³、Jorge Garcia-Franco⁴、Chang-Hyun Park⁵、James Anstey⁶ (1.気象研究所、2.愛知教育大、3.欧州宇宙機関Φラボ、4.コロンビア大学、5.ソウル大、6.カナダ気候モデリング解析センター)

キーワード：QBO、ENSO、遠隔結合

Observations indicate that the quasi-biennial oscillation (QBO) in tropical stratospheric winds can influence the extratropics during winter in both hemispheres, the subtropical jets and tropical precipitation. It is interesting to see whether or not signals of the QBO vary with the El Nino-Southern Oscillation (ENSO) cycle. A previous observational study showed that there are clear variations of the QBO with ENSO, and a recent modeling study from a set of coordinated experiments as part of the Stratosphere-troposphere Processes And their Role in Climate (SPARC) QBO initiative (QBOi) showed that the stratospheric polar vortex response to the QBO is consistent with but weaker than the observations. Here we examine model uncertainties in the representation of QBO teleconnections using a multi-model ensemble of QBO-resolving atmospheric general circulation models that have carried out perpetual El Nino/La Nina/climatology sea-surface temperature anomaly (QBOiENSO) experiments.
By comparing the QBO response between El Nino and La Nina cases, we examine differences in sudden stratospheric warming (SSW) statistics and frequency in the northern (and southern) pole(s), changes to the mean-state and variability of the Walker circulation, convective precipitation in the ITCZ regions, QBO influences on Asia-Pacific jet and its impact on surface climate (focusing on East Asia). It is found that the number of major SSWs seems sensitive to the El Nino/La Nina conditions more in the northern hemisphere, but with large model dependence, and that final warming dates are quite affected in the southern hemisphere, even if models'climatological biases are important.