The quasi-biweekly oscillation of eastern China PM2.5 in response to different Rossby wave trains over the Eurasian continent

Abstract

This study investigates the wintertime quasi-biweekly oscillation characteristic of PM2.5 in eastern China and its relationship with Rossby wave trains propagating over the Eurasian continent. The Empirical orthogonal function (EOF) analysis extracts the three leading modes of PM2.5, including one monopole pattern (Mcon), a north-south dipole pattern (Msn), and a west-east dipole pattern (Mew). The three modes exhibit distinct quasi-biweekly oscillation features (QBWO) under the coupling effects of two Rossby wave trains within the polar front jet and the subtropical westerly jet. The quasi-biweekly evolutions of the Eurasian teleconnection pattern (EU) and Circumglobal teleconnection pattern (CGT) are responsible for the propagation of the two wave trains. The QBWO typical combination cases of the two wave trains are the decay of the EU negative phase and development of the CGT negative phase for Mcon, the development of the EU negative phase and decay of the CGT positive phase for Msn, and the decay of the EU negative phase and development of the CGT positive phase for Mew. A consistent change in surface southerly wind anomalies forms in the north and south when the decay of the EU negative phase works cooperatively with the development of the CGT negative phase, resulting in the PM2.5 monopole pattern (Mcon). The combination case with the development of the EU negative phase and decay of the CGT positive phase favors strong stratification stability in the north and vigorous vertical convection in the south, causing opposing north-south changes in pollutants (Msn). When the decay of the EU negative phase couples with development of the CGT positive phase, surface southerly wind anomalies prevail in the Fenwei Plain, and surface northeasterly wind anomalies from the sea trigger convection in the Yellow River Basin and Huaihe River Basin, forming opposing west-east changes in PM2.5 (Mew).