Understanding the physical processes in the evolution of a cold air outbreak over China in late November 2022 from a Lagrangian perspective

• Published in: Advances in Climate Change Research
• Main Authors: Jin-Ning Che, Bo Liu, Shang-Feng Li, Cheng You, Kara Hartig, Lei Chen
• Format: Article in Journal/Newspaper
• Language: English
• Published: KeAi Communications Co., Ltd. 2023
• Subjects: Cold air outbreak; HYSPLIT; Dry static energy; Temperature tendency; Diabatic heating; Meteorology. Climatology; QC851-999; Social sciences (General); H1-99; Novaya Zemlya; Siberia
• Online Access: https://doi.org/10.1016/j.accre.2023.08.009; https://doaj.org/article/9674ba47d55f4dafbc8a45128b05eb97

From 26 November to 1 December 2022, intense cold air masses swept across China from northwest to south, resulting in a nationwide cold air outbreak (CAO) case characterised by drastic and sudden temperature drops with rain, snow and strong winds. The physical processes that dominate the intensification of the cold air masses during this CAO event remain unclear. In this study, the evolution of the CAO case, which is indicated by the dry static energy (DSE), is investigated using a novel approach in the framework of Lagrangian backtracking. The dominant processes can be identified by decomposing the DSE change into four diabatic heating terms due to shortwave radiation, longwave radiation, latent heat and turbulent processes. Overall, in this case, most of the cold air parcels originated from the east of Novaya Zemlya and crossed Central Siberia before reaching China. Thus, these air parcels mainly manifested on the northwest‒southeast path. The duration of the cold air intensification differed between subregions. The cold air parcels experienced long cooling periods (approximately 9 d) before reaching northern China (i.e. Northwest, North and Northeast China), whilst the southern parts (i.e. Central, East and South China) underwent relatively short cooling periods (6–8 d). Accordingly, the cold air affecting northern China is more intense than that affecting the southern parts, especially for East and South China. For all six subregions, longwave radiative cooling is identified as the dominant contributor to the cold air intensification, and the latent heat processes as the secondary contributor. The weakening of cold air parcels as they approach and pass over these regions is driven by turbulent processes and shortwave heating. Central Siberia and Lake Baikal are identified as key areas for the intensification of cold air passing over both regions. In addition, air parcels affecting Northwest China are intensely cooled as they pass over the Junggar Basin, while the North China Plain is a key area for cooling ...