[A-CG42] Science in the Arctic Region

[ACG42-04] Seasonal Difference in Effect of High-latitude Blocking on Atmospheric Temperature

*Shun Nogawa¹, Masakazu Yoshimori², Masatake E Hori² (1.Department of Earth and Planetary Environmental Science, Faculty of Science, The University of Tokyo, 2.Atmosphere and Ocean Research Institute, The University of Tokyo)

Keywords:Arctic amplification, Atmospheric blocking

In the Arctic region, the strength of meridional temperature gradient, the amount of water vapor in the atmosphere, and the effect of solar radiation differ significantly between summer and winter. Atmospheric blockings, which have close ties with extreme weather events, may differ seasonally in their structure due to the difference in mean atmospheric state, leading to altered effect of blockings toward meteorological variables. In this study, we analyzed the effects of these factors on heat and water vapor transport around blocking and energy balance at the surface. The ERA5 reanalysis dataset provided by the European Centre for Medium-Range Weather Forecasts (ECMWF) were used for the period 1980-2021, where significant atmospheric blocking events were detected using an objective detection method presented in Woollings et al. (2018). To elucidate how atmospheric blocking events influence the temperature changes near the Bering Sea, composite analysis was performed with respect to the central location of the blocking event. Additionally, surface energy balance was investigated to clarify the change in temperature. Our results show that warm anomaly is observed near the center of the blocking in summer, whereas it is located west of the center in winter. It is suggested that warming in summer is primarily caused by increased solar radiation due to the reduction of cloud cover. In winter, water vapor advection and temperature advection play a more significant role. In this study, we highlight the link between the background climatic conditions and the impact of atmospheric blocking.