123 / 2021-07-19 17:30:03

Two types of Rossby wave breaking events and their influences on East Asian winter temperature

Anticyclonic and cyclonic wave breaking events; Low- and high-PV air; the Siberian high; the Arctic Oscillation; Jet stream

Manifested as irreversible overturning of potential temperature contours on the tropopause, the Rossby wave breaking (RWB) can impact mid-latitude weather and climate. Little attention has been paid to the influence of the Rossby wave breaking around East Asia on the East Asian winter climate. The present study reveals that anticyclonic wave breaking (AWB) and cyclonic wave breaking (CWB) events over Siberia and the North Pacific can impact East Asian winter temperature through different dynamical processes. The AWB events are characterized as northeastward intrusion of low-potential vorticity (PV) air from the subtropics and southwestward extension of high-PV air from the high latitudes over the western Siberia. The positive Arctic Oscillation (AO) during the AWB is accompanied by a wave train over Eurasia, contributing to the enhancement of the Siberian high, which causes cold anomalies over East Asia. The CWB events are manifested as northwestward intrusion of low-PV air from the middle latitudes and southeastward extension of high-PV air from the high latitudes over the western North Pacific. The CWB events are associated with the westward retrogression of the blocking over the North Pacific, leading to intensification of the Siberian high. Furthermore, the CWB forces cyclonic anomalies over East Asia, leading to the deepening of the East Asian trough and cold anomalies there. In addition, the CWB events over the western North Pacific can impact the climate over North America via the Rossby wave train emanating from the CWB region.