DOI: 10.1007/s00382-015-2883-8
Scopus记录号: 2-s2.0-84946114019
论文题名: Inter-decadal change in El Niño-Southern Oscillation examined with Bjerknes stability index analysis
作者: An S.-I. ; Bong H.
刊名: Climate Dynamics
ISSN: 9307575
出版年: 2016
卷: 47, 期: 2017-03-04 起始页码: 967
结束页码: 979
语种: 英语
英文关键词: BJ index
; Ekman feedback
; ENSO
; Extreme El Nino
; Interdecadal change
; Mean current damping
; Thermocline feedback
; Thermodynamical damping
; Zonal advection feedback
英文摘要: Characteristics of El Niño-Southern Oscillation (ENSO) have changed since the late 1970s as it synchronized with the Pacific Decadal Oscillation (PDO). In order to investigate the primary feedback process responsible for the interdecadal change in ENSO characteristics according to the PDO, using the ocean assimilation data (SODA) and the reanalysis data (NCEP/NCAR), we performed Bjerknes linear stability index (BJ index) analysis of two decadal periods: one before the late 1970s (the nPDO period) and the other after the late 1970s (the pPDO period). The BJ index for the pPDO period (−0.07 year−1 for the growth rate of the eastern Pacific SST anomaly) is significantly larger than that for the nPDO period (−0.25 year−1). The larger BJ index value is primarily due to the enhanced zonal advection feedback (ZA; +0.44 year−1), thermocline feedback (TH; +0.33 year−1), and the reduced damping by the mean meridional current (MD; +0.16 year−1). The increases in ZA and TH are mainly attributed to the shoaling of the mean thermocline depth, which increased the sensitivity of the ocean dynamic fields to the wind forcing; and the reduced MD is related to the reduced mean meridional current associated with the weakened trade wind. The enhanced positive feedback is partly compensated by the enhanced thermodynamic damping including the shortwave, sensible heat flux and latent heat flux (collectively, −0.88 year−1). Interestingly, the change in air–sea coupling strength from the nPDO to the pPDO period was small. Without the two extreme El Niño events (1982–1983 and 1997–1998) in the pPDO period (pPDO_noBIG), the difference in BJ index between nPDO and pPDO_noBIG periods became smaller (~0.07 year−1), indicating that the two extreme El Niño events largely contribute to the larger ENSO variability of the pPDO period, possibly due to nonlinear feedback processes. Nevertheless, qualitative similarity in each of the feedback and damping components of BJ index exists between the pPDO and pPDO_noBIG periods, which suggests that the tropical climate states of the pPDO period provided more favorable conditions for the emergence of extreme El Niño events by intensifying the linear feedback processes. © 2015, Springer-Verlag Berlin Heidelberg. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/53592
Appears in Collections: 过去全球变化的重建
There are no files associated with this item.
作者单位: Department of Atmospheric Sciences, Yonsei University, Seoul, South Korea
Recommended Citation:
An S.-I.,Bong H.. Inter-decadal change in El Niño-Southern Oscillation examined with Bjerknes stability index analysis[J]. Climate Dynamics,2016-01-01,47(2017-03-04)