Dynamics of Northern Hemisphere Winter Extremes in a Warming Climate

 

Prof. Gang Chen

University of California, Los Angeles, USA

 

邀请人/报告会主持人 ：刘屹岷 研究员

 

2023年5月11日（星期四）10:00

3号楼第三会议室

 

报告摘要:

While midlatitude winter extremes such as cold spells or atmospheric blocking have profound socioeconomic impacts, it remains challenging to understand them and predict their changes in a warming climate. There remains an ongoing debate in the literature about the role of climate warming in recent winter cold extremes over northern continents. In this talk, I will discuss two controversial hypotheses in the literature: 1) will the stratospheric polar vortex stretching, characterized by planetary wave reflection, cause cold extremes over North America and Northern Eurasia; 2) will a weaker midlatitude jet stream under rapid Arctic warming lead to more frequent weather extremes in midlatitudes? A range of theoretical and modeling approaches will be used to address the two questions, which indicate limited support for the proposed changes under climate warming. Rather, I will show that stronger-than-normal stratospheric wave activity provides subseasonal predictability for surface cold extremes and that the spatial shifts of jet streams rather than simple jet speed changes constrain the regional changes of midlatitude circulation waviness. These findings help clarify the dynamics of winter extremes in a warming climate.

 

报告人简介:

Dr. Gang Chen is a professor in the department of Atmospheric and Oceanic Sciences at University of California, Los Angeles.  He received his bachelor’s degree from Peking University in 2002 and Ph.D. degree from Princeton University in 2007.  Prior to UCLA, he worked as postdoctoral fellow at MIT and held faculty position at Cornell University.  His research area is atmospheric and climate dynamics, focusing on atmospheric circulation and chemical transport in a changing climate.