TITLE:
Decadal Variations of Winter Extreme Cold Days in Northern China
AUTHORS:
Wenmao Li, Chaoxia Yuan
KEYWORDS:
Winter Extreme Cold Day, Arctic Oscillation, ENSO
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.7 No.8,
August
26,
2019
ABSTRACT:
Weather and climate extremes often lead to dramatic
losses in our society and warrant improvement of their understanding. In this
study, the decadal variations in the first two dominant empirical orthogonal function (EOF) modes of winter extreme cold days
(WECDs) in northern China (NC) have been investigated. Results show that both
EOF modes show distinct decadal variations that together explain around 24% of
total variances. At the decadal time scale, the EOF1 is closely related to the
decadal Arctic Oscillation (AO); the negative AO can lead to spatially
consistent increase of WECDs in NC. On the other hand, the decadal EOF2 can be
influenced by the decadal El Niño-Southern Oscillation (ENSO). The decadal El
Niño can result in the large-scale negative sea level pressure (SLP) anomalies
in the Eurasian continent west of the western NC and the positive ones over
western China. The anomalous southwesterlies between the contrasted SLP
anomalies can advect the warmer air from the lower latitudes to the western NC,
decrease the WECDs there, and contribute to the east-west asymmetric WECD
anomalies in NC. The impacts of El Niño are confirmed by the numerical
simulations in the Atmospheric Model 2.1 (AM2.1) when forced by the El Niño-related
sea surface temperature (SST) anomalies in the tropical Pacific.