报告题目： Intensification of Arctic Cyclone Activity
Intense cyclones have become more frequently observed in the Arctic, with obvious links to the occurrence of Arctic extreme events. The increase in cyclone activity may also strengthen atmosphere-sea ice-ocean interactions to further amplify long-term Arctic climate change. Therefore, an imperative question to answer is: how have Arctic cyclones changed and how will they change in the future? While previous studies have suggested intensification of Arctic cyclone activity, inconsistencies have also emerged when using different analysis metrics and analyzing different datasets. In this study, we employed an improved, integrative index to analyze variability of and changes in Arctic cyclone activity in multiple state-of-the-art reanalysis datasets. The index aggregates information on cyclone frequency, intensity, and duration. The results indicate that Arctic cyclone activity has intensified during past seven decades. Dynamic mechanism analysis suggests that increased lower troposphere baroclinicity in the Arctic and changes in the large-scale upper tropospheric/stratospheric circulations jointly contributed to the cyclone intensification.
Dr. Xiangdong Zhang is a senior scientist at the North Carolina Institute for Climate Studies and a research professor at the Department of Marine, Earth and Atmospheric Sciences, North Carolina State University. He has conducted integrative research, aiming to improve systematic understanding of the Arctic and Northern Hemisphere climate variability and changes. One of his current responsibilities is to provide scientific input and leadership in the Technical Support Unit and to the National Coordination Office in support the U.S. National Climate Assessment. He is also serving as a member of the CliC-CLIVAR Northern Oceans Region Panel (NORP) and a member of the International Advisory Board of the EU H2020 project PolarRES.