yihua luan, yongqiang yu, weipeng zheng
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University Allied Workshop (2008-7-1). Numerical Study of the Influence of Indian Ocean Dipole Mode (IODM) on Tropical Pacific Ocean ——Roles of the Ocean Dynamic Process. Yihua Luan, Yongqiang Yu, Weipeng Zheng. Institute of atmospheric physics, Chinese Academy of Sciences. Dongliang Yuan - PowerPoint PPT PresentationTRANSCRIPT
Numerical Study of the Influence of Indian Ocean Dipole Mode (IODM) on Tropical
Pacific Ocean——Roles of the Ocean Dynamic Process
Yihua Luan, Yongqiang Yu, Weipeng Zheng Institute of atmospheric physics, Chinese Academy of Sciences
University Allied Workshop
(2008-7-1)
Dongliang Yuan
Institute of Oceanology, Chinese Academy of Sciences
Introduction
Design of the experiments
Features of the OGCM simulation
The influence of IODM on the tropical Pacific Ocean
1 、 Results of the OGCM
2 、 Results of the CGCM
Summary
Outline
Introduction
(Saji et al.,1999)
A composite Indian Ocean Dipole Mode event
Introduction
Atmospheric bridge:
IODM could strengthen the ongoing El Nino using observation data and numerical models to analyze the influence of Indian Ocean SST modes on the ongoing El Nino (Annamalai, et al 2005)
Westerly anomalies over the Indian Ocean could propagate to the tropical Pacific Ocean and affect El Nino (Qingchen Chao, et al 2001)
The Indo-monsoon circulation and the Pacific-Walker circulation have a strong coupling denoted as “GIP”, so the anomalies in the monsoonal zonal flow over the Indian Ocean can affect the air-sea interaction over equatorial Pacific by the virtue of the GIP and trigger off the occurrence of ENSO events
(Meng Wen, Wu Guoxiong 2000,1998 )
IODM could affect the tropical Pacific Ocean through atmospheric remote teleconnections or ocean internal dynamic process
Introduction
Ocean internal dynamic process The closure of ITF makes the eastern tropical Indian Ocean become co
oler and western tropical Pacific Ocean become warmer ( Hirst, A. C., et al.1993 ; Wajsowicz, R. C., et al.2001 )
Question: Can anomalous signal in the Indian Ocean affect Pacific circulation through the ocean internal dynamic process?
IODM could affect the tropical Pacific Ocean through atmospheric remote teleconnections or ocean internal dynamic process
Design of the experiments
OGCM
(LICOM)
In the OGCM experiment, the daily ERA40 wind stress anomaly, heat flux anomaly from 1958-2000 are served as the forcing and the forcing is only applied in the Indian Ocean. The surface forcing over the other regions is the climatological fields
CGCM
(FGOALS_g1.1)
For the CGCM experiment, the regional coupled version of FGOALS_g1.1 is used, only the tropical Pacific (120E-280E,15S-15N) is coupled in the model. The wind stress anomaly, heat flux anomaly of ERA40 and the SST anomaly of GISST of the year 1997 are served as the forcing and the forcing is only applied in Indian Ocean.
OGCM experiment
Fig1 Indian Ocean dipole mode index from 1958-2000( East Indian Ocean: 90E-100E,10S-5N;West Indian Ocean:60E-80E,10S-0 )
1997
Features of OGCM simulation: SST anomalies
Features of OGCM simulation: upper ocean temperature anomalies
IODM effects on the SSH anomalies of Indonesia sea and Pacific Ocean
Results of the OGCM
Following the developing of the IODM, sea level anomalies appear in the Indonesia seas by June and migrate towards east. In August, weak SSH anomalies appear in the western tropical Pacific Ocean
Indonesia
SSH anomalies migrate to the eastern tropical Pacific Ocean in September. A dramatically peaking of SSH anomalies occurs in December
Pacific Ocean
Indonesia
IODM effects on the SST anomalies of Indonesia sea and Pacific Ocean
Pacific Ocean
IODM effects on the upper Pacific Ocean temperature
Design of the CGCM experiments
FGOALS_g1.1: CAM2;LICOM1.11 Coupled region: tropical Pacific Ocean (120E-80W,15S-15N)
Control experiment : climatological fields are specified over the regions out of the c
oupled region.
Sensitive experiment The wind stress anomaly, heat flux anomaly of ERA40 and the
SST anomaly of GISST of the year 1997 are served as the forcing and the forcing is only applied in the Indian Ocean basin.
IODM effects on the tropical Pacific OceanResults of the CGCM
SSTA
IODM effects on the tropical Pacific OceanResults of the CGCM
SSHA
Regional Coupled Model
In other years, tropical Pacific Ocean also makes response to the IODM. But there are different response in El Nino year and Lanina year. The influence process and the mechanism need more research work
Summary
The OGCM LICOM could simulate the IOD event from 1958-2000.
The upper ocean temperature anomalies and sea level anomalies related to the IOD events in the Indian Ocean propagate into the equatorial Pacific Ocean through the Indonesian Seas, and then produce significant SST and sea level anomalies in the eastern equatorial Pacific Ocean.
The regional coupled model could also simulate the propagation of the Indian Ocean abnormal signal into the Tropical Pacific Ocean through the wave process.
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