| GU Dejun,WANG Dongxiao,LI Chunhui,WU Lixin. 2004. Analysis of interdecadal variation of tropical Pacific thermocline based on assimilated data. Acta Oceanologica Sinica, (1):61－72 |
| Analysis of interdecadal variation of tropical Pacific thermocline based on assimilated data |
| Analysis of interdecadal variation of tropical Pacific thermocline based on assimilated data |
| Received:October 03, 2003 Revised:November 11, 2003 |
| DOI： |
| Key words:interdecadal variation thermocline isopycnal surface currents |
| 中文关键词: interdecadal variation thermocline isopycnal surface currents |
| 基金项目: |
| Author Name | Affiliation | E-mail | | GU Dejun | Institute of Tropical and Marine Meteorology, China Meterological Administration, Guangzhou 510080, China
LED, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China | djg@grms.gov.cn | | WANG Dongxiao | LED, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China | | | LI Chunhui | Institute of Tropical and Marine Meteorology, China Meterological Administration, Guangzhou 510080, China | | | WU Lixin | Department of Atmospheric and Oceanic Sciences, University of Wisconsin-Madison, Wisconsin 53706, USA | |
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| Abstract: |
| The interdecadal variation of Pacific thermocline represented by depth anomalies of 25 σθ isopycnal surface calculated from SODA data set is analyzed. The climatological depth of 25 σθ isopycnal surface is quite close to the depth of 20℃ isotherm in the tropical Pacific. The EOF1 mode of the 25 σθ isopycnal surface accounts for 26.4% of the total variance and its associated pattern is of east-west direction. The centers of positive and negative extremes are located near 10°S over the southern Pacific and the correlation coefficient with zero-lag between the corresponding EOF1 time coefficient and PDO index is -0.67. This shows that there is very close relation between the southern tropical Pacific and PDO.The wavelet analysis ofdetrended EOF1 time coefficient reveals that there are two dominant time scales of about 3~7 and 30 a respectively. An apparent abruptness of mean value occurred in the late 1970s. EOF2 mode accounts for 12.4% of the total variance and its pattern is an ENSO-related one. The correlation coefficient between the EOF2 time coefficient and NINO3 index is -0.68. The wavelet analysis of EOF2 time coefficient reveals that there are two leading time scales of about 2~7 and 10~15 a respectively. On an interdecadal scale, the zonal change is consistent along the equator and is seesaw along 10°S; there is consistent polarity in the tropics along 165°E, but reverse polarity between around equator and other tropical region along 120°W. In all the four profiles mentioned above, the regime shift occurred in the late 1970s. The evolving characteristics of anomalies can be explained mostly by the anomalies of ocean currents during a complete cycle on an interdecadal scale. |
| 中文摘要: |
| The interdecadal variation of Pacific thermocline represented by depth anomalies of 25 σθ isopycnal surface calculated from SODA data set is analyzed. The climatological depth of 25 σθ isopycnal surface is quite close to the depth of 20℃ isotherm in the tropical Pacific. The EOF1 mode of the 25 σθ isopycnal surface accounts for 26.4% of the total variance and its associated pattern is of east-west direction. The centers of positive and negative extremes are located near 10°S over the southern Pacific and the correlation coefficient with zero-lag between the corresponding EOF1 time coefficient and PDO index is -0.67. This shows that there is very close relation between the southern tropical Pacific and PDO.The wavelet analysis ofdetrended EOF1 time coefficient reveals that there are two dominant time scales of about 3~7 and 30 a respectively. An apparent abruptness of mean value occurred in the late 1970s. EOF2 mode accounts for 12.4% of the total variance and its pattern is an ENSO-related one. The correlation coefficient between the EOF2 time coefficient and NINO3 index is -0.68. The wavelet analysis of EOF2 time coefficient reveals that there are two leading time scales of about 2~7 and 10~15 a respectively. On an interdecadal scale, the zonal change is consistent along the equator and is seesaw along 10°S; there is consistent polarity in the tropics along 165°E, but reverse polarity between around equator and other tropical region along 120°W. In all the four profiles mentioned above, the regime shift occurred in the late 1970s. The evolving characteristics of anomalies can be explained mostly by the anomalies of ocean currents during a complete cycle on an interdecadal scale. |
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