tianjun zhou - nasa

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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: zhoutj@lasg.iap.ac.cn

In collaboration with B. Wu, H. Li, L. Li, J. Zhang, B. Wang

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Outline

1. Background

2. Interannual variability of Asian monsoon

3. Global monsoon precipitation change

4. E. Asian monsoon circulation change

5. Summary

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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

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JJA Precipitation

CAM T42 observation

TopographyERA40

(Yu et al. 1999)

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How about the performances of AGCMs in simulating the monsoon rainfall variability?

AMIP models

Interannual variability

interdecadal variability

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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 ?

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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)

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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)

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PC time series

CMAP

MME

ERA40

NCEP

NCEP2

(Zhou et al. 2009a J. Climate)

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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)

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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)

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Among the A-AM components, the EA

summer monsoon shows the lowest

reproducibility in interannual variability

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Outline

1. Background

2. Interannual variability of Asian monsoon

3. Global monsoon precipitation change

4. E. Asian monsoon circulation change

5. Summary

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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

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Observation

Simulation

Low skill in Asian-Australian monsoon rainfall

(Zhou et al. 2008a J Climate)

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The specified SST forcing shows the

lowest skill in reproducing the long-term

variability of EA monsoon precipitation

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Outline

1. Background

2. Interannual variability of Asian monsoon

3. Global monsoon precipitation change

4. E. Asian monsoon circulation change

5. Summary

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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)

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Correlations of SSTA with EASM circulation index

CAM3 GOGA

Observation

(Li et al. 2008 Clm Dyn)

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Precipitation: Mean State and Inter-decadal change

GFDL AM2.1 NCAR CAM3

Change

Mean

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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)

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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

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WPSH in IWP warming, cooling and control runs

(Zhou et al. 2009b J Climate)

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JJA precipitation response to Indian Ocean warming:barely any significant signal over E. Asia

(Zhou et al. 2009b J Climate)

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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

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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

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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

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JJA Precipitation in 13 AMIP models

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JJA precipitation in CMIP3

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SSTA regressed upon PC of SEOF1

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(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

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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.