4th International CLIVAR Climate of the 20th Century Workshop, 13-15th March
2007 Hadley Centre for Climate Change, Exeter, UK
The 20th century East Asian summer monsoon
simulated by coupled climate models of IPCC AR4
Tianjun ZHOU
LASG, Institute of Atmospheric Physics, Chinese Academy of
Sciences, Beijing, China
E-mail: [email protected]
Aiguo DAI
National Center for Atmospheric Research, Boulder, CO, USA
1
Outline
Background
Data description
Evaluation of the mean states over E. Asia
Decadal variability of the EASM
Summary
2
Background
 About 25% of humanity inhabits the region of
the East Asian monsoon. The economy and
society across the region are greatly influenced by
the evolution and variability of the monsoon.
The East Asian monsoon climate exhibits
variability on a variety of time scales.
While the interaction of Asian monsoon with
the ENSO is well understood, the monsoon
interdecadal variability is less well
documented and its underlying mechanism is
poorly understood.
3
Data and Approach
 We analyze the outputs of the 20th century climate
simulations (20C3M) of IPCC AR4 coupled models to validate
the realism of current state-of-the-art coupled GCMs in
catching the present climate over East Asia.
We use the model data, combined with observational
evidences, to address the question of whether the prescribed
external forcing agents have played key roles in the variability
of the East Asian monsoon climate in the 20th century.
 Particularly, we want to know the extent to which the 20th
century coupled model integrations can reproduce the
interdecadal variability of the East Asian summer monsoon
(EASM), with a special focus on the recent (1950-1999)
weakening of the EASM, before we apply them to study the
underlying mechanisms.
4
DATA: 20C3M of IPCC AR4
20th Century Climate in Coupled Models (20C3M).
Coordinated by WG1 of IPCC AR4.
The 20th century climate simulations are made with
various combinations of forcings including greenhouse
gases (GHGs), sulfate aerosol effects, and ozone, as
well as volcanic aerosols and solar variability.
 Outputs of 23 coupled models are used in the
analyses.
Zhou Tianjun and Rucong Yu, 2006, Twentieth Century Surface Air
Temperature over China and the Globe Simulated by Coupled Climate
Models, Journal of Climate, 19(22), 5843-5858.
5
East Asian summer monsoon components
Two Key Parts:
WPSH: Z500
EA Jet: U200
(Figure from Ding Yihui)
Zhou Tianjun, Zhaoxin Li, 2002, Simulation of the east Asian summer monsoon by using a
variable resolution atmospheric GCM, Climate Dynamics, 19:167-180
Zhou, T.-J., and R.-C. Yu (2005), Atmospheric water vapor transport associated with typical
anomalous summer rainfall patterns in China, J. Geophys. Res., 10, D08104, doi:10.1029/
2004JD005413
Zhang, Y., X. Kuang, W. Guo, and T. Zhou, 2006, Seasonal evolution of the uppertropospheric westerly jet core over East Asia, Geophys. Res. Lett., 33, L11708,
doi:10.1029/2006GL026377
6
The realism of coupled GCMs in catching the
present climate (1979-1999 JJA state)?
Western Pacific subtropical high (Z500)
East Asian westerly jet (U200)
Rainfall
Assessed by using Taylor Diagram
EAR40 is used as Observation.
Precipitation Data from GPCP.
7
Western Pacific subtropical high (Z500), JJA
Shaded:
Values
lager than
5870 gpm
8
Western Pacific subtropical high (Z500), JJA
(1) bccr_bcm2_0
(2) cccma_cgcm3_1
(3) cccma_cgcm3_1_t63
(4) cnrm_cm3
(5) csiro_mk3_0
(6) gfdl_cm2_0
(7) gfdl_cm2_1
(8) giss_aom
(9) giss_model_e_h
(10) giss_model_e_r
(11) iap_fgoals1_0_g
(12) inmcm3_0
(13) ipsl_cm4
(14) miroc3_2_hires
(15) miroc3_2_medres
(16) mpi_echam5
(17) mri_cgcm2_3_2a
(18) ncar_ccsm3_0
(19) ncar_pcm1
(20) ukmo_hadcm3
(21) ukmo_hadgem1
9
East Asian JJA westerly jet (U200)
10
East Asian JJA westerly jet (U200)
(1) bccr_bcm2_0
(2) cccma_cgcm3_1
(3) cccma_cgcm3_1_t63
(4) cnrm_cm3
(5) csiro_mk3_0
(6) gfdl_cm2_0
(7) gfdl_cm2_1
(8) giss_aom
(9) giss_model_e_h
(10) giss_model_e_r
(11) iap_fgoals1_0_g
(12) inmcm3_0
(13) ipsl_cm4
(14) miroc3_2_hires
(15) miroc3_2_medres
(16) mpi_echam5
(17) mri_cgcm2_3_2a
(18) ncar_ccsm3_0
(19) ncar_pcm1
(20) ukmo_hadcm3
(21) ukmo_hadgem1
11
JJA Rainfall
12
JJA Rainfall
(1) bcc_cm1
(2) bccr_bcm2_0
(3) cccma_cgcm3_1
(4) cccma_cgcm3_1_t63
(5) cnrm_cm3
(6) csiro_mk3_0
(7) gfdl_cm2_0
(8) gfdl_cm2_1
(9) giss_aom
(10) giss_model_e_h
(11) giss_model_e_r
(12) iap_fgoals1_0_g
(13) inmcm3_0
(14) ipsl_cm4
(15) miroc3_2_hires
(16) miroc3_2_medres
(17) mpi_echam5
(18) mri_cgcm2_3_2a
(19) ncar_ccsm3_0
(20) ncar_pcm1
(21) ukmo_hadcm3
(22) ukmo_hadgem1
13
Weakened EASM in Rain Gauge Data
JJA trend in unit of cm/50a from
1958-2000
Normalized time series of JJA
precipitation averaged over the Yangtze
River and Yellow River
14
Weakened EASM Index in Observations
An EASM index is defined as the summation of SLP difference
between 110E and 160E from 10N to 50N. The SLP gradient
between the land and the sea for each year is then divided by its
climate mean value (hereinafter EASM index)
15
EASM index in Coupled Models
Red line is the
observation
16
Correlation coefficients
Model
1880-1999
1900-1949
1950-1999
BCCR-BCM2
0.19
-0.3
0.13
CCSM3
-0.13
-0.4
0.44
CGCM3.1(T47)
0.31
0.02
0.37
CGCM3.1(T63)
-0.25
0.04
-0.41
CNRM-CM3
-0.39
-0.16
-0.63
CSIRO-Mk3.0
0.02
0.40
0.20
ECHAM5/MPI-OM
-0.26
-0.33
-0.26
ECHO-G
-0.03
-0.30
-0.16
FGOALS-g1.0
-0.25
-0.40
-0.27
GFDL-CM2.0
-0.08
-0.32
0.41
GFDL-CM2.1
0.38
0.13
0.73
GISS_AOM
0.25
0.08
0.24
GISS_EH
0.23
0.20
0.03
GISS_ER
0.16
0.27
0.45
INM-CM3.0
0.29
0.39
0.36
IPSL-CM4
0.19
0.22
0.56
MIROC3.2(hires)
0.35
0.0
0.12
MIROC3.2(medres)
0.33
0.05
0.20
MRI-CGCM2.3.2
-0.24
-0.34
0.07
PCM
-0.19
-0.01
-0.25
UKMO-HadCM3
0.37
0.50
-0.08
UKMO-HadGEM1
0.44
0.12
0.34
Correlation
coefficients
between the
simulated and
the observed
EASM Index
on decadal
time scale.
17
Changes in 850 hPa winds and rainfall
(1980-1999) – (1951-1970)
GFDL-CM2.1
HadCM3
HadGEM1
CCSM3
The GFDL and Hadley Centre model produced a weakened EASM !
18
PDF of the weakened EASM in GFDL model
Frequency
PDF from
control run
EASM trend
for 1950-99
in 20th
century run
The EASM
weakening
should be a
forced signal in
GFDL model.
Trend of the ESAM Index
19
Summary
 Many models have reasonable performances in producing the main
monsoon circulations such as the East Asian westerly jet, the western
Pacific subtropical high and the low level monsoon circulations. The
GFDL model seems to have the best performance.
 The decadal variations of the EASM in ten models have significant
correlations with observations during 1880-1999.
 For 1950-1999, the EASM indices of nine models are significantly
correlated with the observations at time scales longer than 10 years.
 Only a small number of models, namely the GFDL-CM2.1, IPSL-CM4,
and HadCM3, have successfully produced the recent weakening trend
of the EASM.
 The weakening trend of the EASM in GFDL-CM2.1 is shown to be a
forced-signal rather than model internal variability.
20
Summary
 Many models have reasonable performances in producing the main
monsoon circulations such as the East Asian westerly jet, the western
Pacific subtropical high and the low level monsoon circulations. The
GFDL model seems to have the best performance.
 The decadal variations of the EASM in ten models have significant
correlations with observations during 1880-1999.
 For 1950-1999, the EASM indices of nine models are significantly
correlated with the observations at time scales longer than 10 years.
 Only a small number of models, namely the GFDL-CM2.1, IPSL-CM4,
and HadCM3, have successfully produced the recent weakening trend
of the EASM.
 The weakening trend of the EASM in GFDL-CM2.1 is shown to be a
forced-signal rather than model internal variability.
21
Summary
 Many models have reasonable performances in producing the main
monsoon circulations such as the East Asian westerly jet, the western
Pacific subtropical high and the low level monsoon circulations. The
GFDL model seems to have the best performance.
 The decadal variations of the EASM in ten models have significant
correlations with observations during 1880-1999.
 For 1950-1999, the EASM indices of nine models are significantly
correlated with the observations at time scales longer than 10 years.
 Only a small number of models, namely the GFDL-CM2.1, IPSL-CM4,
and HadCM3, have successfully produced the recent weakening trend
of the EASM.
 The weakening trend of the EASM in GFDL-CM2.1 is shown to be a
forced-signal rather than model internal variability.
22
Summary
 Many models have reasonable performances in producing the main
monsoon circulations such as the East Asian westerly jet, the western
Pacific subtropical high and the low level monsoon circulations. The
GFDL model seems to have the best performance.
 The decadal variations of the EASM in ten models have significant
correlations with observations during 1880-1999.
 For 1950-1999, the EASM indices of nine models are significantly
correlated with the observations at time scales longer than 10 years.
 Only a small number of models, namely the GFDL-CM2.1, IPSL-CM4,
and HadCM3, have successfully produced the recent weakening trend
of the EASM.
 The weakening trend of the EASM in GFDL-CM2.1 is shown to be a
forced-signal rather than model internal variability.
23
Summary
 Many models have reasonable performances in producing the main
monsoon circulations such as the East Asian westerly jet, the western
Pacific subtropical high and the low level monsoon circulations. The
GFDL model seems to have the best performance.
 The decadal variations of the EASM in ten models have significant
correlations with observations during 1880-1999.
 For 1950-1999, the EASM indices of nine models are significantly
correlated with the observations at time scales longer than 10 years.
 Only a small number of models, namely the GFDL-CM2.1, IPSL-CM4,
and HadCM3, have successfully produced the recent weakening trend
of the EASM.
 The weakening trend of the EASM in GFDL-CM2.1 is shown to be a
forced-signal rather than model internal variability.
24
Thank you ！
http://web.lasg.ac.cn/CSMDA/papers/017.pdf
http://web.lasg.ac.cn/FGCM/publ/ztj2006a.pdf
Zhou Tianjun and Rucong Yu, 2006, Twentieth Century Surface Air
Temperature over China and the Globe Simulated by Coupled
Climate Models, Journal of Climate, 19(22), 5843-5858.
25
Reference for Inter-decadal variability of East Asian climate
1. Zhou Tianjun, Aiguo Dai, and Rucong Yu, 2007, The 20th century East Asian summer
monsoon simulated by coupled climate models of IPCC AR4, a manuscript
2. Yu R.C., and T.J. Zhou, 2007, Seasonality and three-dimensional structure of the
interdecadal change in East Asian monsoon, Journal of Climate, in press
3.
Zhou Tianjun and Rucong Yu, 2006, Twentieth Century Surface Air Temperature over
China and the Globe Simulated by Coupled Climate Models, Journal of Climate, 19(22),
5843-5858.
4.
Xin Xiaoge, Rucong Yu, Tianjun Zhou, and Bin Wang, 2006, Drought in Late Spring of
South China in Recent Decades, Journal of Climate, 19(13), 3197-3206.
5.
Zhou, T.-J., and R.-C. Yu (2005), Atmospheric water vapor transport associated with
typical anomalous summer rainfall patterns in China, J. Geophys. Res., 110, D08104,
doi:10.1029/2004JD005413
6. Li Jian, Rucong Yu, Tianjun Zhou, et al. 2005, Why is there an early Spring cooling shift
downstream of the Tibetan Plateau, Journal of Climate, 18 (22), 4660–4668
7.
Yu Rucong, Bin Wang, and Tianjun Zhou, 2004, Tropospheric cooling and summer
monsoon weakening trend over East Asia, Geophysical Research Letters, 31,L22212,
doi:10.1029 /2004GL021270
8.
Yu Rucong, Tianjun Zhou, 2004, Impacts of winter-NAO on March cooling trends over
subtropical Eurasia continent in the recent half century, Geophysical Research Letters, 31,
L12204, doi:10.1029/2004GL019814.
26