Why were some La Niñas followed by another La Niña?

Hu, Zeng‐Zhen; Kumar, Arun; Xue, Yan; Jha, Bhaskar

doi:10.1007/s00382-013-1917-3

Cited by 102 publications

(87 citation statements)

References 25 publications

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“…11b). This is consistent with the idea that a stronger La Niña will tend to persist longer than a weaker one (Hu et al 2013). Our dynamical analysis indicates that the rate at which heat content is replenished is the main factor governing the duration of La Niña.…”

Section: Precursorssupporting

confidence: 91%

“…The multiyear persistence of La Niña exacerbates its global climate impacts, especially in regions prone to drought. Several observational studies have documented the asymmetry in the duration of the two phases of El Niño-Southern Oscillation (ENSO) (e.g., Kessler 2002;Larkin and Harrison 2002;McPhaden and Zhang 2009;Ohba and Ueda 2009;Wu et al 2010;Okumura and Deser 2010;Ohba et al 2010;Hu et al 2013). For instance, during the 1980-2008 period, sea surface temperature (SST) observations show that La Niña tends to persist into a second year, reintensifying during the following boreal winter (McPhaden and Zhang 2009).…”

Section: Introductionmentioning

confidence: 99%

“…Choi et al (2013) also showed that this nonlinearity plays a role in the asymmetric duration of ENSO events, however, by influencing the termination of La Niña through the delayed adjustment of the thermocline to wind anomalies. Hu et al (2013) argue that ocean dynamical processes involving Kelvin and Rossby waves are key for the persistence of La Niña, but the causes for the persistence of wind anomalies over the western Pacific remain unclear from their study.…”

Section: Introductionmentioning

confidence: 99%

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Nonlinear Controls on the Persistence of La Niña*

2014

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A large fraction (35%-50%) of observed La Niña events last two years or longer, in contrast to the great majority of El Niño events, which last one year. Here, the authors explore the nonlinear processes responsible for the multiyear persistence of La Niña in the Community Climate System Model, version 4 (CCSM4), a coupled climate model that simulates the asymmetric duration of La Niña and El Niño events realistically. The authors develop a nonlinear delayed-oscillator (NDO) model of the El Niño-Southern Oscillation (ENSO) to explore the mechanisms governing the duration of La Niña. The NDO includes nonlinear and seasonally dependent feedbacks derived from the CCSM4 heat budget, which allow it to simulate key ENSO features in quantitative agreement with CCSM4.Sensitivity experiments with the NDO show that the nonlinearity in the delayed thermocline feedback is the sole process controlling the duration of La Niña events. The authors' results show that, as La Niña events become stronger, the delayed thermocline response does not increase proportionally. This nonlinearity arises from two processes: 1) the response of winds to sea surface temperature anomalies and 2) the ability of thermocline depth anomalies to influence temperatures at the base of the mixed layer. Thus, strong La Niña events require that the thermocline remains deeper for longer than 1 yr for sea surface temperatures to return to neutral. Ocean reanalysis data show evidence for this thermocline nonlinearity, suggesting that this process could be at work in nature.

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Section: Precursorssupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Nonlinear Controls on the Persistence of La Niña*

2014

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“…Associated with SSTA, easterly winds ( Fig. 2b) were observed in the central Pacific throughout the year, preventing the propagation of warm water from the western Pacific (Hu et al 2014). The SLA and T e showed similar variations (negative-positive-negative) over the central to eastern basin (Figs.…”

Section: Contrastive Analysismentioning

confidence: 99%

“…As such, although prediction of La Niña is crucial in improving the performance of ENSO models, it has not received the attention that ENSO has (Barnston et al 2012). In particular, the double-dip La Niña event that prevailed over the tropical Pacific during 2011/12, consisting of a second-year cooling at the sea surface following the initial cooling in the fall of 2010, is difficult to predict (Zhang et al 2013;Hu et al 2014;Zheng et al 2015).…”

Section: Introductionmentioning

confidence: 99%

The Role of Stochastic Model Error Perturbations in Predicting the 2011/12 Double-Dip La Niña

Feng

Zheng

Zhu

et al. 2015

SOLA

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The 2011/12 La Niña, referred to as a double-dip La Niña event with following a previous La Niña event, was not well predicted by most climate models when starting from early-mid 2011. Based on a developed El Niño-Southern Oscillation (ENSO) ensemble prediction system, this paper investigates the key predictors for the 2011/12 La Niña, to determine which conditions favor a double-dip La Niña event up to one year in advance. The key predictors were isolated in a 100-member ensemble hindcast experiment. Results show that continuous easterly surface winds and persistent subsurface cold conditions preceded the secondyear cooling in mid-2011. And a significant difference can be viewed between the best and the worst ensemble forecasts arose from the stochastic model-error perturbations. The detailed comparisons between the best and the worst ensemble forecasts further illustrate that the stochastic model-error perturbations play a significant role in improving the prediction skills of the best ensemble members during the 2011/12 12-month forecast process, through capturing the transition of sea surface temperature (SST) over the tropical Pacific (i.e., from a warm condition to a cold condition) in boreal spring.(Citation: Feng, L., F. Zheng, J. Zhu, and H. Liu, 2015: The role of stochastic model error perturbations in predicting the 2011/ 12 double-dip La Niña. SOLA, 11, 65−69,

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