Dongqian Wang
Bing Zhou Chenghu Sun
The features of EAWM 2012/13 and possible influencing factors
Beijing Climate Center04-09-2013
1) The climate in DJF 2012/13
2) Features of 2012/13 EAWM
3) Possible influencing factors of EAWM
4) Summary
Outline
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.
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 ). ℃
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
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.
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
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
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
)6040;12080( NESLPSH
EAWM
The first threecomponents of EOF of winter temperature fields
Temperature anomalies in winter 2012/13
EAWMAtmospheric circulation anomalies correspond to EAPC-1
Atmospheric circulation anomalies in winter 2012/13
EAWM
850hPa wind anomalies correspond to EAPC-1
850hPa wind anomalies in winter 2012/13
southerly wind anomalies
easterly wind anomalies
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
a) AO
Arctic Oscillation kept negative phase
Correlation between AO
and Surface air temperature
Correlation between AO
and 200hPa zonal wind
b) pre-autumn Artic sea ice
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
weak polar vortex in the stratosphere
stratospheric sudden warming
Downward propagation of positive stratospheric anomalies
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
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
2) Features of 2012/13 EAWM
3) Possible influencing factors of EAWM
4) Summary
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.