学術雑誌論文 Relationship between the Arctic oscillation and surface air temperature in multi-decadal time-scale

10 ( 3 )  , pp.199 - 209 , 2016-09
ISSN:18739652
内容記述
In this study, a simple energy balance model (EBM) was integrated in time, considering a hypothetical long-term variability in ice-albedo feedback mimicking the observed multi-decadal temperature variability. A natural variability was superimposed on a linear warming trend due to the increasing radiative forcing of CO2. The result demonstrates that the superposition of the natural variability and the background linear trend can offset with each other to show the warming hiatus for some period. It is also stressed that the rapid warming during 1970–2000 can be explained by the superposition of the natural variability and the background linear trend at least within the simple model. The key process of the fluctuating planetary albedo in multi-decadal time scale is investigated using the JRA-55 reanalysis data. It is found that the planetary albedo increased for 1958–1970, decreased for 1970–2000, and increased for 2000–2012, as expected by the simple EBM experiments. The multi-decadal variability in the planetary albedo is compared with the time series of the AO mode and Barents Sea mode of surface air temperature. It is shown that the recent AO negative pattern showing warm Arctic and cold mid-latitudes is in good agreement with planetary albedo change indicating negative anomaly in high latitudes and positive anomaly in mid-latitudes. Moreover, the Barents Sea mode with the warm Barents Sea and cold mid-latitudes shows long-term variability similar to planetary albedo change. Although further studies are needed, the natural variabilities of both the AO mode and Barents Sea mode indicate some possible link to the planetary albedo as suggested by the simple EBM to cause the warming hiatus in recent years.
本研究では、雪氷アルベドフィードバックを考慮したエネルギーバランスモデル(EBM)を用いて、地上気温の長周期変動の再現を試みた。その結果、自然変動と人為的温暖化トレンドが打ち消し合うことで近年の温暖化ハイエイタスが再現された。また、両者の重ね合わせで1970~2000年の急速な温暖化も再現された。JRA-55再解析データを用いて長周期変動の鍵となるプラネタリーアルベドの変動を解析した結果、半球平均値は1958~1970年で増加、1970~2000年で減少、2000~2012年で増加を示し、EBMと整合的な結果が得られた。さらに、プラネタリーアルベドの長周期変動は、地上気温のバレンツ海モードの変動と一致しており、近年の北極振動(負)の空間パターンとも整合的である。本研究の結果から、長周期変動に及ぼすこれらの自然変動の重要性が示唆された。

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