Contrasting Indian Ocean SST variability with and without ENSO influence: A coupled atmosphere-ocean GCM study

Yu, Jin‐Yi; Lau, K.-M.

doi:10.1007/s00703-004-0094-7

Cited by 80 publications

(56 citation statements)

References 35 publications

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“…After the EP-El Niñ o reaches its peak phase, the western anomaly center of the IOD spreads eastward and evolves into a basinwide warming. This IOD and Indian Ocean warming sequence is similar to that discussed by and Yu and Lau (2004). The composite analyses suggest that the IOD mode has a tendency to appear during EP-El Niñ o events, but more research is needed to have a better understanding of the linkage between them.…”

Section: Phase Locking To the Seasonal Cycle And The Evolutions Of Thsupporting

confidence: 73%

Contrasting Eastern-Pacific and Central-Pacific Types of ENSO

2009

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Surface observations and subsurface ocean assimilation datasets are examined to contrast two distinct types of El Niñ o-Southern Oscillation (ENSO) in the tropical Pacific: an eastern-Pacific (EP) type and a central-Pacific (CP) type. An analysis method combining empirical orthogonal function (EOF) analysis and linear regression is used to separate these two types. Correlation and composite analyses based on the principal components of the EOF were performed to examine the structure, evolution, and teleconnection of these two ENSO types. The EP type of ENSO is found to have its SST anomaly center located in the eastern equatorial Pacific attached to the coast of South America. This type of ENSO is associated with basinwide thermocline and surface wind variations and shows a strong teleconnection with the tropical Indian Ocean. In contrast, the CP type of ENSO has most of its surface wind, SST, and subsurface anomalies confined in the central Pacific and tends to onset, develop, and decay in situ. This type of ENSO appears less related to the thermocline variations and may be influenced more by atmospheric forcing. It has a stronger teleconnection with the southern Indian Ocean. Phase-reversal signatures can be identified in the anomaly evolutions of the EP-ENSO but not for the CP-ENSO. This implies that the CP-ENSO may occur more as events or epochs than as a cycle. The EP-ENSO has experienced a stronger interdecadal change with the dominant period of its SST anomalies shifted from 2 to 4 yr near 1976/77, while the dominant period for the CP-ENSO stayed near the 2-yr band. The different onset times of these two types of ENSO imply that the difference between the EP and CP types of ENSO could be caused by the timing of the mechanisms that trigger the ENSO events.

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Section: Phase Locking To the Seasonal Cycle And The Evolutions Of Thsupporting

confidence: 73%

Contrasting Eastern-Pacific and Central-Pacific Types of ENSO

2009

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“…5a) are confined more to the eastern Pacific and South American coast and resemble the spatial structure and temporal evolution of the EP El Niño. Ocean is known to be forced by traditional EP El Niño events through an anomalous Walker circulation (e.g., Klein et al 1999;Yu and Lau 2005;Xie et al 2009;Kumar et al 2014). Therefore, the 3-5-yr band of WPSH variability can be considered as a WPSH response to the forcing from the EP El Niño and the associated Indian Ocean warming.…”

Section: Fig 2 (A)mentioning

confidence: 99%

A Source of AGCM Bias in Simulating the Western Pacific Subtropical High: Different Sensitivities to the Two Types of ENSO

Paek

Hwu³

et al. 2015

Monthly Weather Review

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This study reveals a possible cause of model bias in simulating the western Pacific subtropical high (WPSH) variability via an examination of an Atmospheric Model Intercomparison Project (AMIP) simulation produced by the atmospheric general circulation model (AGCM) developed at Taiwan's Central Weather Bureau (CWB). During boreal summer, the model overestimates the quasi-biennial (2-3 yr) band of WPSH variability but underestimates the low-frequency (3-5 yr) band of variability. The overestimation of the quasibiennial WPSH sensitivity is found to be due to the model's stronger sensitivity to the central Pacific El Niño-Southern Oscillation (CP ENSO) that has a leading periodicity in the quasi-biennial band. The model underestimates the low-frequency WPSH variability because of its weaker sensitivity to the eastern Pacific (EP) ENSO that has a leading periodicity in the 3-5-yr band. These different model sensitivities are shown to be related to the relative strengths of the mean Hadley and Walker circulations simulated in the model. An overly strong Hadley circulation causes the CWB AGCM to be overly sensitive to the CP ENSO, while an overly weak Walker circulation results in a weak sensitivity to the EP ENSO. The relative strengths of the simulated mean Hadley and Walker circulations are critical to a realistic simulation of the summer WPSH variability in AGCMs. This conclusion is further supported using AMIP simulations produced by three other AGCMs, including the CanAM4, GISS-E2-R, and IPSL-CM5A-MR models.

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“…The complicated relationship of the IODZM with SST anomalies over the Pacific could be a contributing factor Yamagata et al, 2004). Some authors like Chambers et al (1999); Allan et al (2001); Banquero et al (2002); Dommenget and Latif (2002); Hastenrath (2002); Shinoda et al (2004); Yu and Lau (2004) argue that IODZM events are triggered by ENSO and hence are not independent of ENSO. While on the other hand, others like Webster et al (1999) ;Iizuka et al (2000); Rao et al (2002); Yamagata et al (2002); Ashok et al (2003); Gualdi et al (2003); Lau and Nath (2004); Behera et al (2005) contradict these findings by presenting the independence of the IODZM mode from ENSO.…”

Section: Introductionmentioning

confidence: 99%

The impact of the positive Indian Ocean dipole on Zimbabwe droughts

Manatsa

Chingombe

Matarira

2008

Intl Journal of Climatology

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A comparative study of the impact of the anomalous positive Indian Ocean SST gradient, referred to as the Indian Ocean Dipole/Zonal Mode (IODZM), and El Niño-Southern Oscillation (ENSO) on Zimbabwe seasonal rainfall variability for the period 1940-1999, is documented. Composite techniques together with simple and partial correlation analyses are employed to segregate the unique association related to IODZM/ENSO with respect to the Zimbabwe seasonal rainfall.The analysis reveals that the IODZM impact on the country's summer rainfall is overwhelming as compared to that of ENSO when the two are in competition. The IODZM influence remains high (significant above 99% confidence level), even after the influence of ENSO has been removed, while that of ENSO collapses to insignificance (even at 90% confidence level) when the IODZM contribution is eliminated. The relationship between ENSO and Zimbabwe seasonal rainfall seems to be sustained through El Niño occurring in the presence of positive IODZM events. However, when the co-occurring positive IODZM and El Niño events are removed from the analysis, it is apparently clear that ENSO has little to do with the country's rainfall variability. On the other hand, positive IODZM is mostly associated with the rainfall deficits, whether or not it co-occurs with El Niño. However, the co-occurrence of the two events does not necessarily suggest that El Niño influences droughts through the positive IODZM events. The El Niño event components during co-occurrence seem to be unrelated (at least linearly) to the droughts, while the positive IODZM events display a relatively strong relationship that is significant above the 95% confidence level. It thus becomes important to extend the study of this nature to cover the whole of southern Africa, so that the extent of the impact of the phenomena can be realized over the whole region.

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Contrasting Indian Ocean SST variability with and without ENSO influence: A coupled atmosphere-ocean GCM study

Cited by 80 publications

References 35 publications

Contrasting Eastern-Pacific and Central-Pacific Types of ENSO

Contrasting Eastern-Pacific and Central-Pacific Types of ENSO

A Source of AGCM Bias in Simulating the Western Pacific Subtropical High: Different Sensitivities to the Two Types of ENSO

The impact of the positive Indian Ocean dipole on Zimbabwe droughts

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