1. Dongqian Wang Bing Zhou Chenghu Sun The features of EAWM 2012/13 and possible influencing factors Beijing Climate Center 04-09-2013

2. 1) The climate in DJF 2012/13 2) Features of 2012/13 EAWM 3) Possible influencing factors of EAWM 4) Summary Outline

3. 冷！ cold 暖！ warm Temperature Anomalies (DJF 2012/13) colder than normal in most places of the world. 1-4 ℃ below normal in central- northeastern Asia, with temperatures more than 4 ℃ below normal in northern East Asian and parts of southern Russia.

4. Monthly Temperature Anomalies Dec 2012 Jan 2013 Feb 2013 strong intra-seasonal variations 8-12 ℃ below normal in central and western Siberia in December, and in late winter, the colder regions shifted eastward.

5. DJF Temperature index of China In DJF 2012/13, the seasonal mean temperatures over China was -3.7°C, with 0.3°C below normal (-3.4 ℃ ).

6. Stronger Siberian High and EAWM Smallest Arctic Sea Ice extent in Sep. since 1979. Slighter stronger Indian Ocean(IOBW). CGCM1.0/BCC Slight weaker Arctic Oscillation cold warm cold Slight stronger Tibetan Plateau Height Prediction of Winter Temperature Anomaly over China

7. - + C C CGCM1.0/BCC for Atmospheric Circulation in DJF

8. Precipitation Anomalies (DJF 2012/13) 少！ 多！ dry wet 50-100% more than normal in most West Asia, Central Asia, central South Asia, most Northeast China at least 50% less than normal in central-northern Russia, most Southwest China.

9. 1) The climate in DJF 2012/13 2) Features of 2012/13 EAWM 3) Possible influencing factors of EAWM 4) Summary

10. Time series of EAWM index StrongWeak EAWM =U500(80-120E;25-35N)-U500(80-120E,50-60N) as proposed by Y.F Zhu(2008) East Asian winter monsoon (EAWM) was in the stronger than normal period of inter-decadal variation, was stronger than normal for 6th consecutive year

11. Time series of SH index The Siberian High (SH) was also in the stronger than normal period of inter-decadal variation, but in last winter, SH was weaker than normal

12. EAWM The first three components of EOF of winter temperature fields Temperature anomalies in winter 2012/13

13. EAWM Atmospheric circulation anomalies correspond to EAPC-1 Atmospheric circulation anomalies in winter 2012/13

14. EAWM 850hPa wind anomalies correspond to EAPC-1 850hPa wind anomalies in winter 2012/13 southerly wind anomalies easterly wind anomalies

15. Daily Siberian High index exhibited strong intra-seasonal variations, stronger than normal in the early winter, weaker than normal in the middle winter and changed from strong to weak in the late winter

16. Daily EAWM index StrongWeak strong intra-seasonal variations

17. 1) The climate in DJF 2012/13 2) Features of 2012/13 EAWM 3) Possible influencing factors of EAWM 4) Summary

18. a) AO

19. Arctic Oscillation kept negative phase

20. Correlation between AO and Surface air temperature Correlation between AO and 200hPa zonal wind

21. b) pre-autumn Artic sea ice

22. Distribute of pre-autumn Artic sea ice Arctic sea ice extent was significantly lower than normal since summer 2012. The Arctic Sea Ice Extent and concentration in Sep.2012 are the smallest since 1979

23. Studies show that ASI anomaly in Sep. has significantly negative correlation with Siberian High.

24. c) Propagation of positive stratospheric anomalies

25. weak polar vortex in the stratosphere stratospheric sudden warming Downward propagation of positive stratospheric anomalies

26. 150hPa outgoing heat flux 20hPa zonal wind an anomalous strengthen of outgoing heat flux the convergence of heat flux at stratosphere lead to the deceleration of polar night jet suppressed the outgoing of heat flux, lead to a sudden warming happened in the stratosphere. The atmospheric circulation adjust to the radiation balance in the non-adiabatic process, resulting in strengthen of polar night jet. In this process, polar night jet was weaker than normal, which was conducive to the changing of AO from positive to negative, or the persistence of negative AO

27. The 1000hPa GPH anomalies composited with respect to positive anomaly downward propagation events (Chen, 2009) 01.11-02.28 mean SLP anomalies

28. 1) The climate in DJF 2012/13 2) Features of 2012/13 EAWM 3) Possible influencing factors of EAWM 4) Summary

29. Summary In DJF 2012/2013, temperatures were extremely below normal over East Asian, with key circulations as following: -The EAWM intensity exhibited strong intra-seasonal variations -Arctic Oscillation kept negative phase -Low pre-autumn Arctic Sea ice might be the influencing factors on EAWM -The downward propagation of stratospheric anomalies was the possible causes of intra-seasonal climatic variation over East Asian.