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Dongqian Wang Bing Zhou Chenghu Sun

The features of EAWM 2012/13 and possible influencing factors. Dongqian Wang Bing Zhou Chenghu Sun. Beijing Climate Center 04-09-2013. Outline. 1) The climate in DJF 2012/13 2) Features of 2012/13 EAWM 3) Possible influencing factors of EAWM 4) Summary.

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Dongqian Wang Bing Zhou Chenghu Sun

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

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

  3. Temperature Anomalies (DJF 2012/13) 冷！ cold warm 暖！ 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. Prediction of Winter Temperature Anomaly over China Stronger Siberian High and EAWM Smallest Arctic Sea Ice extent in Sep. since 1979. cold cold Slight weaker Arctic Oscillation Slighter stronger Indian Ocean(IOBW). warm Slight stronger Tibetan Plateau Height CGCM1.0/BCC

  7. Precipitation Anomalies (DJF 2012/13) 多！ wet 少！ dry 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.

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

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

  10. 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

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

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

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

  14. 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

  15. Daily EAWM index Strong Weak strong intra-seasonal variations

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

  17. a) AO

  18. Arctic Oscillation kept negative phase

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

  20. b) pre-autumn Artic sea ice

  21. 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

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

  23. c) Propagation of positive stratospheric anomalies

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

  25. suppressed the outgoing of heat flux, lead to a sudden warming happened in the stratosphere. an anomalous strengthen of outgoing heat flux 150hPa outgoing heat flux 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 20hPa zonal wind The atmospheric circulation adjust to the radiation balance in the non-adiabatic process, resulting in strengthen of polar night jet. the convergence of heat flux at stratosphere lead to the deceleration of polar night jet

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

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

  28. 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.

  29. Thank you！

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