Possible Dynamic Mechanisms of High‐ and Low‐Latitude Wave Trains Over Eurasia and Their Impacts on Air Pollution Over the North China Plain in Early Winter. Issue 13 (30th June 2022)

• Record Type: Journal Article
• Authors: An, Xiadong; Chen, Wen; Fu, Shuo; Hu, Peng; Li, Chun; Sheng, Lifang
• Is Part Of: Journal of geophysical research. Volume 127:Issue 13(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-06-30
• Subjects: Rossby wave train -- El Niño -- air‐sea interaction -- bifurcation -- air pollution -- North China Plain; Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1029/2022JD036732
• Languages: English
• ISSNs: 2169-897X

Abstract

Abstract: The Rossby wave train in boreal winter sometimes bifurcates into two branches near the Mediterranean, sometimes not. However, causes for bifurcating of the wave train are still being debated. Additionally, discussions about the differences in the deterioration ability of these wave trains on air pollution are also insufficient. This study uses the empirical orthogonal function (EOF) to obtain two dominant modes of the November‐January season wave trains over Eurasia and discusses their different influences on air pollution over the North China Plain (NCP). From the EOF1 mode, bifurcation of the wave train appears to stem from the Rossby wave reflection near the Mediterranean because the Rossby wave source is located outside of a strong absolute vorticity gradient. From the EOF2 mode, the wave train propagates only along the subtropical westerly jet because the Rossby wave source is located inside of a strong absolute vorticity gradient, so that the wave train tends to be refracted near the Mediterranean. In addition, the wave train associated with the EOF1 is suggested to be related to the eastern Pacific El Niño. The eastern Pacific El Niño tends to force a wave train propagating into East Asia under the charger effect from positive feedback of air‐sea coupling near the far eastern Atlantic and Mediterranean, while the wave train associated with the EOF2 is suggested to be mainly induced by natural internal variability. Furthermore, the results indicate that the bifurcation type wave train tends to cause higher PM2.5 concentrations over the NCP through a strengthened Northeast Asia anomalous anticyclone. Plain Language Summary: In this study, we find that bifurcation of the wave train over Eurasia is related to the Rossby wave source near the Mediterranean. The wave train tends to bifurcate into two branches when the Rossby wave source is located outside a strong gradient of absolute vorticity near the Mediterranean and vice versa. Further results reveal that the branched wave train is related to the eastern Pacific El Niño. Positive feedback of air‐sea coupling plays a key role in the propagation of the eastern Pacific El Niño‐related wave train over Eurasia. The energy equation reveals that the wave train only along the subtropical westerly jet might be a product of natural internal variability. Compared with the wave train only along the subtropical westerly jet, the bifurcation type wave train leads to higher PM2.5 concentrations over the North China Plain. Key Points: Rossby wave source located north to strong absolute vorticity gradient may lead to wave train bifurcation near the Mediterranean Positive feedback of air‐sea coupling over far eastern Atlantic and Mediterranean supports the eastern Pacific El Niño‐related wave train over Eurasia The bifurcating wave train in early winter tends to cause higher PM2.5 concentrations over the North China Plain