Climatology of Northeast China cold vortices during the warm season: A comparison of ERA5 and MERRA-2 reanalysis
Abstract
The Northeast China cold vortex (NCCV) is an important type of synoptic scale system, which often induces local torrential rainfall events, strong winds, and lightning during warm seasons (MaySeptember). By using an automatic identification method that involves a three-step algorithm, NCCVs during warm seasons from 19802018 were identified from ERA5 and MERRA-2, the latest generation of reanalyses. Validation of the reproducibility of NCCVs for the two reanalyses shows that the three-step algorithm can identify most NCCVs from these two reanalysis datasets with an accuracy of approximately 90%. Based on this recognition result and intensive surface observations, climatology of the NCCV was analyzed. With respect to mean climatology, the results indicate that the average 500-hPa trough of NCCV hours is mainly located east of the Yablonov Mountains to the west of the Xiao Hinggan Mountains. The average NCCV rain belt falls within Northeast China, the Korean Peninsula, and southern Japan. With regard to interannual variation, the NCCV hours were more in the latest 9 years than in the two previous 15-year cycles. The intensity alteration is complex; in May and June, strong NCCVs show a strengthening trend, while weak NCCVs show a weakening trend. Additionally, from July to September, there is an overall weakening trend. In terms of intraseasonal variation, NCCVs are usually generated at the border area between China, Mongolia, and Russia, then develop and move eastward, and finally disappear in Heilongjiang Province, China and its neighboring southeastern Russia. NCCVs move in complex paths (Fig.1); from 2016 to 2018, 38%61% of NCCVs moved southeastward or eastward, 26%46% of NCCV paths were significantly turned and knotted, 8.7%15.4% of NCCVs moved northeastward, and 0%4% moved northwestward. The above results based on advanced reanalyses with high resolutions updated to 2018 are a renewal and a supplement to previous related studies to further improve our understanding of the NCCV, especially that of its movement characteristics. Meanwhile, the comparative analysis reveals the commonalities and subtle differences between the two reanalyses.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2021
- Bibcode:
- 2021AGUFM.A25P1879G