The Frequency of Extreme Cold Events in North China and Their Relationship with Sea Surface Temperature Anomalies

Abstract

This study investigated the interdecadal characteristics of the frequency of the winter single station extreme cold events (SSECEs) in North China and their relationship with sea surface temperature (SST). The results showed the following: (a) The SSECEs occurred frequently before 1991, but less thereafter, with an increase after 2018. The first two interdecadal modes of the SSECE frequency were east–west inverse and “n” patterns. (b) The interdecadal abrupt change of the “n” pattern occurred around 1997/1998. Before 1997/1998, the synergistic effects between the positive Interdecadal Pacific Oscillation (+IPO) and the negative North Atlantic Multidecadal Oscillation (−AMO) triggered the “two troughs and one ridge” anomalous circulation in Eurasia. The Rossby wave energy propagated downstream from the Atlantic, strengthening the Lake Baikal ridge. Furthermore, the Siberian High (SH) became weaker in the north and stronger in the south. With the favorable jet conditions, the cold air invaded North China along the northerly airflow in front of the Lake Baikal ridge, resulting in the frequent SSECE occurrence in central North China. Afterwards, the opposite occurred. (c) The cooperation of SST anomalies (SSTAs) led to the east–west inverse anomaly of the SSECE frequency. Before 1991, the high SSTAs in the central North Atlantic and low SSTAs in the equatorial Indian Ocean and the southwest Pacific triggered “+”, “−”, “+”, and “−” wave trains at mid-latitudes from the Atlantic to the North Pacific. The Rossby wave energy propagated eastward from the Atlantic, resulting in the SH and Urals ridge strengthening, and the Aleutian Low and East Asian trough deepening. The northwestern airflow in front of the Urals ridge guided the cold air into North China, leading to frequent SSECEs in central and eastern North China before 1991. The opposite occurred between 1992 and 2018.