Variations In Frequency Of Winter Extreme Cold Days In Northern China And Possible Causalities

Extreme cold weather and climate often result in catastrophe in northern China(NC)and thus need to enhance their understanding.In this study,the frequency of winter extreme cold day(WECDs)in NC have been investigated.Results show that the first EOF mode reflects the spatially consistent anomalies of WECDs in NC and explains 39%of total variances.The second EOF mode presents the east-west contrasted anomalies in NC and explains 17%of total variances.In the winter when the negative AO(Arctic Oscillation)co-occurs with the stronger Siberian High(SH),cold air from the polar region will lead to the increased frequency of WECDs in the whole NC.The negative AO and stronger SH may be related to the excessive snow in the preceding autumn in the Eurasian continent through the local snow-albedo feedback and the tropospheric-stratospheric interaction.On the other hand,when the negative AO co-occurs with the weaker SH,the eastern NC is still under the influences of cold air intrusion related to negative AO,while the western NC is impacted by the anomalous warm air advection related to the weaker SH.The weakening of SHwell simulated the causing process and the more WECDs in western NC may be caused by the El Nino teleconnection The GFDL AM2.1 SST sensitivie experimentThe multi-model ensemble of the ten coupled models participating CMIP5 have a good ability to reproduce the observed first and second EOF modes of the WECDs in NC and related large-scale circulation anomalies.Therefore,it is appropriate to use the multi-model ensemble of these models to study and predict the variations of extreme low temperature in NC.