Interdecadal Variations of ENSO around 1999/2000

• Published in: Journal of Meteorological Research 2017-02, Vol.31 (1), p.73-81
• Main Authors: Hu, Zeng-Zhen, Kumar, Arun, Huang, Bohua, Zhu, Jieshun, Ren, Hong-Li
• Format: Article
• Language: English
• Subjects: Atmospheric Protection/Air Quality Control/Air Pollution; Atmospheric Sciences; Earth and Environmental Science; Earth Sciences; ENSO预测; Geophysics and Environmental Physics; Meteorology; 南方涛动; 厄尔尼诺; 年代际变化; 气候系统; 热带太平洋; 赤道太平洋; 频率变化
• ISSN: 2095-6037; 2198-0934
• DOI: 10.1007/s13351-017-6074-x

This paper discusses the interdecadal changes of the climate in the tropical Pacific with a focus on the correspond- ing changes in the characteristics of the E1 Nifio-Southern Oscillation （ENSO）. Compared with 1979-1999, the whole tropical Pacific climate system, including both the ocean and atmosphere, shifted to a lower variability regime after 1999/2000. Meanwhile, the frequency of ENSO became less regular and was closer to a white noise process. The lead time of the equatorial Pacific＇s subsurface ocean heat content in preceding ENSO decreased remarkably, in addition to a reduction in the maximum correlation between them. The weakening of the correlation and the shorten- ing of the lead time pose more challenges for ENSO prediction, and is the likely reason behind the decrease in skill with respect to ENSO prediction after 2000. Coincident with the changes in tropical Pacific climate variability, the mean states of the atmospheric and oceanic components also experienced physically coherent changes. The warm an- omaly of SST in the western Pacific and cold anomaly in the eastern Pacific resulted in an increased zonal SST gradi- ent, linked to an enhancement in surface wind stress and strengthening of the Walker circulation, as well as an in- crease in the slope of the thermocline. These changes were consistent with an increase （a decrease） in precipitation and an enhancement （a suppression） of the deep convection in the western （eastern） equatorial Pacific. Possible con- nections between the mean state and ENSO variability and frequency changes in the tropical Pacific are also dis- cussed.