Seasonal Climate Outlook for Summer 2013 Ke Zongjian, Wang Yongguang Beijing Climate Center...
-
Upload
barbra-hubbard -
Category
Documents
-
view
213 -
download
0
Transcript of Seasonal Climate Outlook for Summer 2013 Ke Zongjian, Wang Yongguang Beijing Climate Center...
Seasonal Climate Outlook for Summer 2013
Ke Zongjian, Wang Yongguang
Beijing Climate Center
2013.04.09
BCC-CGCM forecast
ROC area (above)Probability forecast for
precipitation
Statistical correction to Dynamical modelFODAS
FODAS forecast based on BCC-CGCM and statistical methods-Feng G L et alMODES forecast based on four models and statistical methods-Liu C Z et al
MODES
Forecast
ACC
PDO is in cold phase
ColdWarm
50年代 60年代 70年代 80年代 90年代 21世纪
Decadal variation of PDO and summer rain belt
1950s 1960s 1970s 1980s 1990s 2000~2008 2009~2012
1.Influencing factor —SST
Forecasted SST by dynamical models
SST anomaly in last winter
Tropical SST is not conducive for western North Pacific subtropical high (WNPSH) to be very strong or weak
2. influencing factor—snow cover
Snow anomaly over Northern hemisphere in DJF
Eurasia
Tibetan Plateau
Northeast China
Less snow cover over Tibetan Plateau in
winter and spring
Sensible heat is stronger and ascending
activity is stronger in spring and summer
Stronger heating in troposphere warm the
air
Thermodynamic difference increases
between Tibetan Plateau and southern Sea
Stronger East Asian summer monsoon
(EASM, Zhang Q Y et al., 2003)
More rainfall in North China, South China
while less rainfall in Yangtze River valley.
Less snow cover over Tibetan Plateau, less rainfall in Yangtze River valley
2.1 snow cover over Tibetan Plateau
Zhang S L et al, 2001. Atmos. Scien. (Chinese)
More snow less snow
+
-
-
+
-
+
More snow cover over eastern Siberia in winter, less rainfall in Yangtze River valley
Xu L Y and Wu B Y , 2012 , Chinese J. Atmos. Sci. More snow cover over eastern Siberia in winter will result in more thawy snow in spring. The anomaly
mode of thawy snow over eastern Siberia is accordant with variation of EASM. More thawy snow will
trigger longitudinal negative-positive-negative anomaly wave train of 500 hPa geopotential height in
East Asia. It will strengthen EASM and result in less rainfall in Yangtze River valley.
--
+
2.2 snow cover over Eurasia
precipitation anomaly500 hPa geopotential height
Zhao et al., 2004. J. C.
Mechanism
Wu B Y et al , 2004 , Polar res.(Chinese)
More Bering sea ice, less rainfall in Yangtze River valley
3.Influencing factor– sea ice
Less ice in Barents Sea, Kara Sea in winter, more ice in Bering Sea in spring
Difference of rainfall between less ice and more ice
Sea ice anomaly over Northern hemisphere in DJF
Interannual variation of Western North Pacific Subtropical High (WNPSH) in JJA
Axis position
Intensity
west boundary
jul-Aug
More northward for WNPSH, less rainfall in Yangtze River valley
1981-2010
Correlation between summer rainfall and axis position of WNPSH
Summary
WNPSH will be slightly stronger and northward
than normal
EASM will be stronger than normal
More precipitation will be in North China, while
less precipitation along the Yangtze River valley.
Precipitation prediction in JJA 2013
moremore
more
more
more
less
Thanks for your attention!
EASMI
IEASM =U850(10 ~ 20N,100 ~ 150E)
-U850 (25 ~ 35N,100 ~ 150E)
Zhang Q Y et al., 2003, Acta Metero. Sinica (Chinese) Bin wang et al., 2008 , J. C.
How to represent East Asian summer monsoon
EASM will be a little stronger than normal
Precursor of EASM (IF):IF =U200( 80-110E, 32.5-37.5) - U200( 150-120W, 22.5-27.5N)
R = 0.66 ( 1981-2010)
Strong EASM
Weak EASM
Zhang Q Y et al., 2003, Acta Metero. Sinica (Chinese)
Stronger East Asian summer monsoon, less rainfall in Yangtze River valley
Corr. between summer rainfall and EASM
WNPSH in JJA from dynamical models
IAP9L blue dashed line, climatology
IAP2L red line, climatology
BCC-CGCM1 red line, climatology
WNPSH is stronger and more westward than climatology