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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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The features of EAWM 2012/13

and possible influencing factors

Dongqian Wang

Bing Zhou Chenghu Sun

Beijing Climate Center

04-09-2013


Outline
Outline

1) The climate in DJF 2012/13

2) Features of 2012/13 EAWM

3) Possible influencing factors of EAWM

4) Summary


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.


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.


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℃).


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


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.


1) The climate in DJF 2012/13

2) Features of 2012/13 EAWM

3) Possible influencing factors of EAWM

4) Summary


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)


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


EAWM

The first three

components of EOF of winter temperature fields

Temperature anomalies in winter 2012/13


EAWM

Atmospheric circulation anomalies in winter 2012/13

Atmospheric circulation anomalies correspond to EAPC-1


EAWM

850hPa wind anomalies correspond to EAPC-1

easterly wind anomalies

southerly wind anomalies

850hPa wind anomalies in winter 2012/13


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


Daily EAWM index

Strong

Weak

strong intra-seasonal variations


1) The climate in DJF 2012/13

2) Features of 2012/13 EAWM

3) Possible influencing factors of EAWM

4) Summary




Correlation between AO

and Surface air temperature

Correlation between AO

and 200hPa zonal wind



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


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


C propagation of positive stratospheric anomalies
c) Propagation of positive stratospheric anomalies negative correlation with Siberian High.


Downward propagation of positive stratospheric anomalies negative correlation with Siberian High.

weak polar vortex in the stratosphere

stratospheric sudden warming


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


The 1000hPa GPH anomalies composited with respect to positive anomaly downward propagation events

(Chen, 2009)

01.11-02.28 mean SLP anomalies


1) The climate in DJF 2012/13 positive anomaly downward propagation events

2) Features of 2012/13 EAWM

3) Possible influencing factors of EAWM

4) Summary


Summary positive anomaly downward propagation events

  • 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.


Thank positive anomaly downward propagation eventsyou!


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