Modulation of South Asian Jet Wave Train on the Extreme Winter Precipitation over Southeast China Comparison between 2015/16 and 2018/19

• Published in: Journal of climate Vol. 33; no. 10; pp. 4065 - 4081
• Main Authors: Li, Xiuzhen, Wen, Zhiping, Huang, Wan-Ru
• Format: Journal Article
• Language: English
• Published: Boston American Meteorological Society 15.05.2020
• Subjects: Advection; Anticyclones; El Nino; Extreme weather; Planetary waves; Precipitation; River valleys; Rivers; Rossby waves; Spatial distribution; Storms; Studies; Transport; Wave packets; Wave propagation; Wave trains; Wavelength; Wind; Winter precipitation; China; Bay of Bengal; Japan; Yangtze River
• DOI: 10.1175/jcli-d-19-0678.1
• ISSN: 0894-8755

Two extremely wet winters in 2015/16 and 2018/19 over Southeast China are compared in this study. South-to-north discrepancies appear in the spatial distribution of precipitation, with anomalous precipitation centered over the southeast coast in 2015/16 and the lower reaches of Yangtze River valley in 2018/19, respectively. Both instances of enhanced precipitation are ascribed mainly to warm and moist advection from the south, with transport in 2015/16 partly by a deepened India–Burma trough to the west, whereas with transport in 2018/19 mainly by a subtropical western North Pacific anticyclone (WNPAC). Both the India–Burma trough and WNPAC are maintained by the wave trains propagating along the South Asian jet, which are zonally offset by a quarter-wavelength. Further study of the wave train sources in 2015/16 and 2018/19 shows that they both tend to originate from extremely strong storm-track activity over the North Atlantic but have different displacement. The former is located more northeastward than the mean storm track and is modulated by a strong positive NAO, whereas the latter lies over the midlatitude central North Atlantic along with a circumglobal teleconnection. These differences further result in a quarter-wavelength offset in the Rossby wave source near the entrance of the South Asian jet by the convergence of upper-level divergent wind.