Journal Article

Features of Local Finite-Amplitude Wave Activity during Extreme Cold Waves over Eastern China

Ekwacu, Samuel, Shi, Ning, Fu, Shiyi, Song, Jian, Xing, Shaoying

2023

Overview

The frequent occurrence of extreme cold waves under climate change has attracted widespread attention. Based on the Japanese 55-year Reanalysis daily dataset from 1958 to 2021, we use a newly developed dynamic metric, the local finite-amplitude wave activity (LWA), to explore the precursory signals, outburst conditions, and key dynamic features of extreme cold waves over eastern China from the perspective of synoptic climatology. The statistical results show that approximately 40% of extreme cold waves have the following features. First, the formation of significant positive LWA anomalies over the Balkhash–Baikal region is an evident precursory signal, which is accompanied by significant cold surface air temperature anomalies that accumulate over mid- and high-latitude Eurasia. Second, the appearance of extreme positive LWA anomalies over the region east of Lake Baikal (ELB) is necessary for subsequent outbursts of extreme cold waves. These extreme positive LWA anomalies indicate the meridionally enhanced planetary trough over East Asia and advection of the accumulated cold air masses southeastward to eastern China. Third, the evident positive change in the LWA anomalies over the ELB is mainly attributable to the convergence of the zonal LWA flux due to the zonal wind in the eddy-free state and Stokes drift flux over the eastern area of the ELB and the convergence of the meridional eddy heat flux over the western area. This study demonstrates that the LWA could be used as a simple and feasible metric for monitoring and forecasting extreme cold waves.

• Publisher: American Meteorological Society
• Subject: Advection / Air masses / Air temperature / Amplitude / Amplitudes / Anomalies / Climate change / Climatic extremes / Climatology / Cold / Cold air masses / Cold surfaces / Cold waves / Convergence / Eddy heat flux / Extreme cold / Fluctuations / Forecasting / Heat flux / Heat transfer / Latitude / Monitoring methods / Outbursts / Stokes drift / Surface temperature / Surface-air temperature relationships / Synoptic climatology / Temperature anomalies / Waves / Waviness / Zonal winds