[A-CG52] Science in the Arctic Region

[ACG52-P10] Modulation of the Ural Blocking and its Effects on Extreme Temperature Events under Progressing Global Warming

*Masatake Hori¹, Masakazu Yoshimori¹, Jinro Ukita¹ (1.University of Tokyo, Atmosphere Ocean Research Institute)

Keywords:Global warming, Atmospheric blocking, Extreme temperature

Drastically changing climate in the Arctic due to progression of global warming has lead to concerns regarding the shift in frequency and intensity of atmospheric variability which in turn influences severe weather conditions such as extremes in temperature. One of the key feature of this variability is the existance of the Ural anticyclonic height anomaly (UAA) which brings persistent warm advection from the mid-latitudes into the higher latitudes during the cold season. Here, we investigate the modulation of UAA by use of blocking indices and elucidate its influence towards extreme temperature in the region using a large ensemble climate simulation dataset, the database for Policy Decision making for Future climate change (d4PDF). Difference in frequency of blocking occurrence under 4K global warming experiment (HFB-4K) compared to the non-warming experiment (HPB-NAT) exhibit a sustained increase over the Ural region during the cold season of October through March. Taking a composite of temperature anomalies associated with UAA reveals a distinct positive (warm) signal along the coast of the Eurasian continent and a negative (cold) signal in the mid-latitudes. Distribution of lower tropospheric daily temperature reveals that difference in daily temperature distribution between HFB-4K and HPB-NAT is dominated by the difference in mean temperature due to global warming. However, comparing the temperature anomaly relative to the respective climatology shows a suppression of variance under HFB-4K in the warm anomaly region but not in the cold anomaly regions. Extreme temperature under Ural anticyclonic anomaly also shows a suppression of warm extreme in the warm anomaly region. It is shown that a weaker meridional temperature gradient due to strong Arctic warming acts to weaken the warm advection in the higher latitude thereby suppressing the occurrence of extreme temperature anomaly under extreme global warming.