Severe Extreme Cold Event in Beijing-Tianjin-Hebei Region Tied to Mid-High-Latitude Intraseasonal Waves

Abstract

Extreme cold events (ECEs) have intensified in East Asia over the past decades, disrupting socio-economic activities and public health. Understanding the mechanism and accurate prediction are crucial yet challenging. This study explores the causes and prediction biases for a severe ECE in Beijing-Tianjin-Hebei (BTH) during the 2022 Winter Olympics. Two upper-tropospheric quasi-biweekly oscillations (QBWO), propagating eastward along the mid- and high-latitudes, respectively, have been confirmed to trigger a low-tropospheric cyclonic anomaly (LCA) via potential vorticity advection and meridional secondary circulation. This LCA generated the BTH ECE by reducing incoming solar radiation due to increased snowfall and cloud cover, and by advecting cold air into BTH. Both the subseasonal dynamical prediction and long-term historical observational diagnosis further indicate a strong connection between mid-high-latitude QBWO and the regional ECEs. This research deepens our understanding of the ECE mechanisms and underscores the need for improving the prediction of extratropical subseasonal signals for better forecasting of extreme events.