Abstract:

Utilizing meteorological observatory data of daily minimum temperature from 1961 to 2019 in Beijing-Tianjin-Hebei region of China, along with NOAA′s monthly sea surface temperature and NCEP/NCAR′s monthly 500 hPa geopotential height field, this study employs physical statistical methods to analyze the variation characteristics of the number of strong cold air days during winter in the region and its relation to sea surface temperatures. This study also explains the mechanism behind the Pacific North American (PNA) teleconnection pattern influenced by sea temperatures in the Niño 3.4 region. The results indicate that the average annual number of strong cold air days in Beijing-Tianjin-Hebei region varies between 0.0 to 8.7 days, with a spatial distribution decreasing from northwest to southeast. Interannually, the number of strong cold air days during winter in Beijing-Tianjin-Hebei significantly correlating with the preceding summer, autumn, and concurrent winter sea temperatures are mainly in the central and eastern equatorial Pacific. Significant negative correlation areas in the westerly jet region and northeastern North Atlantic appear in the preceding autumn and concurrent winter. A pronounced positive correlation with the equatorial Indian Ocean is maintained concurrently. Anomalies in the winter strong cold air days in Beijing-Tianjin-Hebei region are influenced by variations of 500 hPa geopotential height field features such as the Ural Mountain high-pressure ridge, Baikal Lake low-pressure, the anomalous high-pressure over mid-low latitudes of East Asia, and the East Asian trough. Concurrently, sea temperature anomalies in the Niño 3.4 region affect the variation of height field through the PNA teleconnection pattern, indirectly influencing the number of strong cold air days in the region.

Key words: Strong cold air, Sea surface temperature, PNA teleconnection