tianjun zhou - nasa
TRANSCRIPT
1
LASG, Institute of Atmospheric Physics, Chinese Academy of Sciences, China
How well do AMIP models simulate the interannual and interdecadal variability of Asian monsoon: State of affairs and challenges
Tianjun ZHOU
Workshop on High-Resolution Climate Modeling, August 10-14, 2009, ICTP, Italy
Email: [email protected]
In collaboration with B. Wu, H. Li, L. Li, J. Zhang, B. Wang
2
Outline
1. Background
2. Interannual variability of Asian monsoon
3. Global monsoon precipitation change
4. E. Asian monsoon circulation change
5. Summary
3
Target domain
Western Pacific Western Pacific Subtropical HighSubtropical High
Mid-high latitude processes
MeiyuFront
TyphoonTyphoon
Plateau forcing
Monsoon low
DD
Somali jet
Mascarene High Australian High
Tropical convectionTropical convectionEastward Eastward
propagation of MJOpropagation of MJO
Sw lowD
Monsooon trough
5
JJA Precipitation
CAM T42 observation
TopographyERA40
(Yu et al. 1999)
6
How about the performances of AGCMs in simulating the monsoon rainfall variability?
AMIP models
Interannual variability
interdecadal variability
7
Observational analysis has identified two leading modes of the AAM:
--The first mode exhibits a prominent biennial tendency and concurs with El Nino
-- The second mode leads the Pacific warming by one year, providing a precursor for El Niño/La Niña development(Wang et al. 2007).
A
A
C
A
A
C
C
C
27.4% 10.6%
Interannual variability modes of precipitation and 850 hPa wind in observation
S-EOF analysis; from JJA(0) to MAM(1)
How well do AGCMs reproduce these leading modes ?
8
11 AMIP AGCMs
Institute AGCM Resolution Name used in the discussion
UKMO HadGAM1 N96L38 HadGEM1NCAR CAM3 T85L26 CCSM3MRI - T42L30 CGCM2_3_2aMPI ECHAM5 T63 L32 ECHAM5
CCSR MIROC3_2(medres) T42L20 MIROC3_2_medresCCSR MIROC3_2(hires) T106 L56 MIROC3_2_hiresINM - 4.0o lat x5.0o lon L21 INMCM3_0
IAP GAMIL 2.8o lat x2.8o lon L26 FGOALS1_0_gNASA/GISS - 4.0o lat x5.0o lon L20 GISS_E_R
GFDL - 2.0o lat x2.5o lon L24 GFDL_AM2
CNRM - T42 L45 CNRM_CM3
Model outputs cover the period 1979-1999.
(Zhou et al. 2009a J. Climate)
9
S-EOF modes of MME precipitation and the associated 850hPa wind
SEOF1(31.3%) SEOF2 (12.8%)
0.65
0.75
0.81
0.66
0.41
0.56
0.62
0.81
A
A
C
C
C
A
A
(Zhou et al. 2009a J. Climate)
10
PC time series
CMAP
MME
ERA40
NCEP
NCEP2
(Zhou et al. 2009a J. Climate)
11
Comparison of AMIP against the observed dominant S-EOF modes of precipitation
Correlation coefficients between the observed and simulated anomalies (or PCs)(Zhou et al. 2009a J. Climate)
12
Spatial pattern of correlation coefficients between the
observed and AMIP MME rainfall anomalies.
High skill in tropical region
Nearly no skill in summertime WNP monsoon area.
Better in winter
(Zhou et al. 2009a J. Climate)
13
Among the A-AM components, the EA
summer monsoon shows the lowest
reproducibility in interannual variability
14
Outline
1. Background
2. Interannual variability of Asian monsoon
3. Global monsoon precipitation change
4. E. Asian monsoon circulation change
5. Summary
15
Changes of JJA Rainfall(1981-2000 minus 1958-1977)
(Xin et al. 2006 J. Climate; Zhou et al. 2009, Meteorologische Zeitschrift )
An overall weakening tendency of global land monsoon precipitation intensity in the last 56 years (1948-2003)
(Wang and Ding, 2006,GRL)
The EOF1 of normalized annual range anomalies (upper) and the corresponding PC (lower).
The first EOF of normalized annual range anomalies (upper) and the corresponding principle component (lower).
CC=0.60
(Zhou et al. 2008a J. Climate)
Rainfall Anomaly Pattern
Monsoon Rainfall index
Global land monsoon precipitation change(CAM2 T42, Global SST-driven, 15 realizations)
18(Zhou et al. 2008a J Climate)
OBS
Model
SSTA congruent with the weakening trend of global land monsoon precipitation
19
Observation
Simulation
Low skill in Asian-Australian monsoon rainfall
(Zhou et al. 2008a J Climate)
20
The specified SST forcing shows the
lowest skill in reproducing the long-term
variability of EA monsoon precipitation
21
Outline
1. Background
2. Interannual variability of Asian monsoon
3. Global monsoon precipitation change
4. E. Asian monsoon circulation change
5. Summary
22
NCEP/NCAR
GFDL AM2.1 GOGA
NCAR CAM3 GOGA
E. Asian Summer monsoon circulation index
( Li et al. 2008 Clm Dyn )
NCAR CAM3 TOGA
5 realizations
10 realizations
(T42+T85)
23
Correlations of SSTA with EASM circulation index
CAM3 GOGA
Observation
(Li et al. 2008 Clm Dyn)
24
Precipitation: Mean State and Inter-decadal change
GFDL AM2.1 NCAR CAM3
Change
Mean
25
The monsoon rain band is controlled by the Western Pacific Subtropical High
MeiyuMeiyu FrontFront
Subtropical High
Courtesy of Huang R. (2007)
26Contour lines for 5870 gpm of 500 hPa geo-potential height for each summer
1980-99
1958-79
NCEP/NCAR ERA40
Westward Extension of WPSH
(Zhou et al. 2009b J Climate)
27SST [1950-1975] – SST[1960-1990]
SST [1976-2001] – SST[1960-1990]
SST averaged over the entire basin
The warming tendency of Indian Ocean
(Casso et al. 2008)
28
Institute AGCM Resolution Convection scheme Reference
NCAR CAM3 T85L26
Deep convection is parameterized following Zhang and McFarlane (1995). Shallow and upper-level convection uses Hack (1994).
Boville et al. (2006)
MPI ECHAM5 T63 L31Tiedtke(1989) with modifications for deep convection according to Nordeng(1994).
Hagemann et al. (2006)
UKMO HadAM3 2.5o lat X 3.75o
lon L19
Gregory and Rowntree (1990) with the addition of convective downdrafts (Gregory and Allen 1991)
Pope et al. (2000)
IAP GAMIL 2.8o lat x2.8o
lon L26 Zhang‐McFarlane(1995) Wang et al.(2004)
CNRM ARPEGE T63 L31
Deep convection is represented by a mass flux scheme with detrainment as proposed by Bougeault (1985). The stratiform and shallow convection cloud formation is evaluated via a statistical method described in Ricardand Royer (1993)
Cassou et al. (2001)
Description of 5 AGCMs
29
WPSH in IWP warming, cooling and control runs
(Zhou et al. 2009b J Climate)
30
JJA precipitation response to Indian Ocean warming:barely any significant signal over E. Asia
(Zhou et al. 2009b J Climate)
31
The specified SST forcing produces a
reasonable responses in monsoon
circulations, but barely any signal in
monsoon rainfall
1. The AMIP MME captures the leading modes of monsoon variability with a skill that is
comparable to reanalysis in terms of the seasonally evolving spatial patterns and the
corresponding temporal variations, as well as their relationships with ENSO.
2. The skill of AMIP simulation is season-dependent. The DJF (JJA) has the highest
(lowest) skill. Over the East Asia, extra-tropical western North Pacific and South
China Sea, the MME shows nearly no skill in JJA.
3. The topical Ocean warming is one mechanism for the weakening tendency of global
land monsoon rainfall and E. Asian Monsoon Circulation. The decadal scale westward
extension of WPSH is partly driven by the warming of Indian Ocean.
4. The AGCMs succeed in simulating the EA monsoon circulation change, but fail in
simulating the EA monsoon rainfall change.
Summary
Can high resolution modeling improve the EA
monsoon rainfall simulation in both mean
state and multi-scale variabilities ?
Issues call for further investigation
34
CCSR, MRI high resolution modeling
GFDL C180 simulation, 1981-2005
Met Office, N48, N96, N144, N216 , 25 years of AMIP2
GEOS-5 simulation: C180-55km C360-27km C720—14km C1440-
6.9km C2880—3.4 km C5760—1.7km, case simulations for tropical
cyclone to be used in monsoon studies
COLA SP-CCSM
SNUAGCM 25 km simulation
Schubert Proposal: Data sharing in regional studies
as suggested by Dr. K.-M. Lau
Expected collaborative efforts
35
1. Zhou, T., B. Wu, and B. Wang, 2009a: How well do Atmospheric General Circulation
Models capture the leading modes of the interannual variability of Asian-Australian
Monsoon? J. Climate, 22, 1159-1173
2. Zhou, T., R. Yu, J. Zhang, H. Drange et al. 2009b, Why the Western Pacific Subtropical
High has extended westward since the late 1970s, J. Climate, 22, 2199-2215
3. Zhou, T., Yu R., Li H., et al. 2008a, Ocean forcing to changes in global monsoon
precipitation over the recent half century, J. Climate, 21, (15), 3833–3852
4. Zhou, T., Bo Wu, A. A. Scaife, S. Bronnimann, et al., 2008b, The CLIVAR C20C Project:
Which components of the Asian-Australian Monsoon circulation variations are forced and
reproducible? Climate Dynamics, DOI 10.1007/s00382-008-0501-8
5. Li, H., A. Dai, T. Zhou, J. Lu, 2008, Responses of East Asian summer monsoon to
historical SST and atmospheric forcing during 1950-2000, Climate Dynamics, DOI
10.1007/s00382-008-0482-7
Some further readings
http://web.lasg.ac.cn/staff/ztj/index_e.htm
37
JJA Precipitation in 13 AMIP models
38
JJA precipitation in CMIP3
39
SSTA regressed upon PC of SEOF1
40
(105°-122°E average T and latitude –height cross-section)
1977-2000 minus1950-1976NCEP/NCAR
1977-2000 minus1950-1976AM2.1 GOGA
CAM3 GOGA CAM3 TOGA
+ -
+
+
+- -
-
(Li et al. 2008 Clm Dyn)
Land-Sea thermal contrast change
41
CAM3 T42 RADATM
CAM3 T42 GOGAI-GOGA
CAM3 T85 GOGAI-GOGA
Aerosol Forcing ?
E. Asian Summer monsoon index
AM2.1 GOGAI-GOGA
(Li et al. 2008 Clm Dyn; consistent with Li et al. 2007 GRL)
The prescribed aerosol forcing is the same as 20C3M.