The Seasonal Forecast of the Precipitation in China in

the Summer of 2013

国际气候与环境科学中心International Center for Climate and Environment Sciences

Peng Jingbei

The Institute of Atmospheric Physics(IAP), CAS

EASM System

IAP’s Climate Forecast

ENSO forecast systems

CGCMEnsemble

system

AGCMs

2L 9L

CGCM

CCSM4.0

Statistical MethodsENSO SNOW

Atmospheric Signal

EASM

Subtropical High

precipitation

Seasonal Forecast

IAP’s Forecast of ENSO

IAP’s CGCM-Nino3IAP’s Large-Size Ensemble ENSO Forecast System with Coupled Data Assimilation-Nino3.4

The ENSO-neutral will continue through the next several months.

IAP-2L-AGCM IAP-9L-AGCM

CCSM4

Forecast of the Subtropical High

Red- model’s long-term mean Green -prediction

Blue-model’s long-term mean Red- prediction

Blue-model’s long-term mean Red- prediction

The subtropical high will be stronger than usual in summer of 2013

Forecast of EASMSnow Cover over the Tibetan Plateau

(Provided by BCC/CMA)

More Snow →Colder TP surface in spring and summer → Weaker temperature contrast → Weaker EASM

Less snowStronger EASM

Forecast of EASM

The EASM Forecast Index

U’200 in Feb 2013

+U’200 → the Jet shifted northward→ less precipitation in the South Asia→ land-sea contrast ↑→stronger EASM (Zhang et al., 2003 ）

The Drought monitor in Feb 2013 （ BCC/CMA ）

Positive Correlation with EASM IndexStronger EASM

Precipitation Prediction（Numerical Models）

2L-AGCM 9L-AGCM

CCSM4

Composed Summer Rainfall Anomaly Percentage

during the Decaying Phase of LN

Seasonal Forecast

Thank You

H500 Anomalies2L 9L

CCSM4

UV’8502L 9L

CCSM4

CCSM4 Prediction Skills(Correlation Coefficients with NCEP Reanalysis Data)

East Asia Winter Monsoon (EAWM)

+SSTAs in South China Sea(SCS)

Frontier

Stronger EAWM→-SSTAs in SCS in Winter→-SSTAs in Summer→Land-Sea Contrast↑→EASM Stronger（ Ji et al.， 1997）

SS

TAs

in D

JF

Index of EAWMPositive-Weaker

SS

TAs

in J

JA

Experiment of Ensemble Prediction of EASM Index of

2013

L2 L9 EAWM U’200 (FEB)

0.41 0.39 0.51 0.72

Ensemble Prediction

Contradictions in Prediction of EASM of 2013

Correlations with Observation EASM Index during 1982-2012

L2 L9 CCSM4.0 EAWM U’200 (FEB)

-0.02 -0.66 0.7 Weaker Stronger

Predictors Prediction Examination(Correlation)

L2+L9+EAWM+U’200 (FEB)

-0.07 0.64

EAWM+U’200 (FEB)

0.18 0.71

东亚地区的 2013年夏季降水异常

mm/day

预测意见：2013年我国夏季气候环流：夏季风正常，副高偏西偏北；降水：我国南方降水偏少，北方降水偏多；

• A global atmospheric general circulation model developed at the Institute of Atmospheric Physics (IAP), Chinese Academy of Sciences (CAS) . (Zeng, 1987; Zhang, 1990; Liang, 1996; Bi, 1993)

Horizontal Resolution: 4o×5o ;

Vertical Resolution: 9 levels, with a top at 10hPa.

IAP9L-AGCM

Lower boundary conditions: Over the tropical Pacific region, the SSTA used in IAP9L-AGCM is the linear combination of observed SSTA in initial month and SSTA forecasted by IAP ENSO prediction system：

The initial atmospheric data and observed SSTA are from NCEP. The ensemble consists of seven integrations starting form last seven consecutive days in or Oct.

(SSTA)t=(t) [(SSTA)to]Obs+ [1-(t)][ (SSTA)Fcst]t

Here, (t) varies from 1.0 to 0.0 during the integration time

Over other regions, SSTA is kept as the observed SSTA in initial month.

The Large-size Ensemble ENSO Forecast System with Coupled Data Assimilation

• Zheng, Zhu, et. al. GRL, 2006