Season-dependent predictability and error growth dynamics for La Nina predictions

2020 ◽  
Author(s):  
Junya Hu ◽  
Wansuo Duan ◽  
Qian Zhou
Keyword(s):  
Growth Phase ◽  
Equatorial Pacific ◽  
Prediction Errors ◽  
Error Growth ◽  
Central Pacific ◽  
Initial Errors ◽  
Eastern Equatorial Pacific ◽  
Type 2 Errors

<p>The “spring predictability barrier” (SPB) is a well-known characteristic of ENSO prediction, which has been widely studied for El Niño events. However, due to the nonlinearity of the coupled ocean–atmosphere system and the asymmetries between El Niño and La Niña, it is worthy to investigate the SPB for La Niña events and reveal their differences with El Niño. This study investigates the season-dependent predictability of sea surface temperature (SST) for La Niña events by exploring initial error growth in a perfect model scenario within the Community Earth System Model. The results show that for the prediction through the spring season, the prediction errors caused by initial errors have a season-dependent evolution and induce an SPB for La Niña events. Two types of initial errors that often yield the SPB phenomenon are identified: the first are type-1 initial errors showing positive SST errors in the central-eastern equatorial Pacific accompanied by a large positive error in the upper layers of the eastern equatorial Pacific. The second are type-2 errors presenting an SST pattern with positive errors in the southeastern equatorial Pacific and a west–east dipole pattern in the subsurface ocean. The type-1 errors exhibit an evolving mode similar to the growth phase of an El Niño-like event, while the type-2 initially experience a La Niña-like decay and then a transition to the growth phase of an El Niño-like event. Both types of initial errors cause positive prediction errors for Niño3 SST and under-predict the corresponding La Niña events. The resultant prediction errors of type-1 errors are owing to the growth of the initial errors in the upper layers of the eastern equatorial Pacific. For the type-2 errors, the prediction errors originate from the initial errors in the subsurface layers of the western equatorial Pacific. These two regions may represent the sensitive areas of targeted observation for La Niña prediction. In addition, the type-2 errors in the equatorial regions are enlarged by the recharge process from 10°N in the central Pacific during the eastward propagation. Therefore, the off-equatorial regions around 10°N in the central Pacific may represent another sensitive area of La Niña prediction. Additional observations may be prioritized in these identified sensitive areas to better predict La Niña events.</p>

scholarly journals Optimally growing initial errors of El Niño events in the CESM

2021 ◽  
Author(s):  
Hui Xu ◽  
Lei Chen ◽  
Wansuo Duan
Keyword(s):  
El Niño ◽  
El Nino ◽  
Equatorial Pacific ◽  
Initial Error ◽  
Initial Errors ◽  
El Niño Events ◽  
Type 3 ◽  
El Nino Events

AbstractThe optimally growing initial errors (OGEs) of El Niño events are found in the Community Earth System Model (CESM) by the conditional nonlinear optimal perturbation (CNOP) method. Based on the characteristics of low-dimensional attractors for ENSO (El Niño Southern Oscillation) systems, we apply singular vector decomposition (SVD) to reduce the dimensions of optimization problems and calculate the CNOP in a truncated phase space by the differential evolution (DE) algorithm. In the CESM, we obtain three types of OGEs of El Niño events with different intensities and diversities and call them type-1, type-2 and type-3 initial errors. Among them, the type-1 initial error is characterized by negative SSTA errors in the equatorial Pacific accompanied by a negative west–east slope of subsurface temperature from the subsurface to the surface in the equatorial central-eastern Pacific. The type-2 initial error is similar to the type-1 initial error but with the opposite sign. The type-3 initial error behaves as a basin-wide dipolar pattern of tropical sea temperature errors from the sea surface to the subsurface, with positive errors in the upper layers of the equatorial eastern Pacific and negative errors in the lower layers of the equatorial western Pacific. For the type-1 (type-2) initial error, the negative (positive) temperature errors in the eastern equatorial Pacific develop locally into a mature La Niña (El Niño)-like mode. For the type-3 initial error, the negative errors in the lower layers of the western equatorial Pacific propagate eastward with Kelvin waves and are intensified in the eastern equatorial Pacific. Although the type-1 and type-3 initial errors have different spatial patterns and dynamic growing mechanisms, both cause El Niño events to be underpredicted as neutral states or La Niña events. However, the type-2 initial error makes a moderate El Niño event to be predicted as an extremely strong event.

scholarly journals The interplay of thermodynamics and ocean dynamics during ENSO growth phase

2020 ◽  
Author(s):  
Tobias Bayr ◽  
Annika Drews ◽  
Mojib Latif ◽  
Joke Lübbecke
Keyword(s):  
Heat Flux ◽  
Latent Heat Flux ◽  
Growth Phase ◽  
Climate Models ◽  
Phase Locking ◽  
Equatorial Pacific ◽  
Heat Fluxes ◽  
Ocean Dynamics ◽  
Eastern Equatorial Pacific ◽  
Atmospheric Heat

AbstractThe growth of El Niño/Southern Oscillation (ENSO) events is determined by the balance between ocean dynamics and thermodynamics. Here we quantify the contribution of the thermodynamic feedbacks to the sea surface temperature (SST) change during ENSO growth phase by integrating the atmospheric heat fluxes over the temporarily and spatially varying mixed layer to derive an offline “slab ocean” SST. The SST change due to ocean dynamics is estimated as the residual with respect to the total SST change. In observations, 1 K SST change in the Niño3.4 region is composed of an ocean dynamical SST forcing of + 2.6 K and a thermodynamic damping of − 1.6 K, the latter mainly by the shortwave-SST (− 0.9 K) and latent heat flux-SST feedback (− 0.7 K). Most climate models from the Coupled Model Intercomparison Project phase 5 (CMIP5) underestimate the SST change due to both ocean dynamics and net surface heat fluxes, revealing an error compensation between a too weak forcing by ocean dynamics and a too weak damping by atmospheric heat fluxes. In half of the CMIP5 models investigated in this study, the shortwave-SST feedback erroneously acts as an amplifying feedback over the eastern equatorial Pacific, resulting in a hybrid of ocean-driven and shortwave-driven ENSO dynamics. Further, the phase locking and asymmetry of ENSO is investigated in the CMIP5 model ensemble. The climate models with stronger atmospheric feedbacks tend to simulate a more realistic seasonality and asymmetry of the heat flux feedbacks, and they exhibit more realistic phase locking and asymmetry of ENSO. Moreover, the almost linear latent heat flux feedback contributes to ENSO asymmetry in the far eastern equatorial Pacific through an asymmetry in the mixed layer depth. This study suggests that the dynamic and thermodynamic ENSO feedbacks and their seasonality and asymmetries are important metrics to consider for improving ENSO representation in climate models.

Errors

2017 ◽  
Author(s):  
Mark Harrison
Keyword(s):  
Emergency Medicine ◽  
Type 2 Errors

This chapter describes types of errors as applied to Emergency Medicine, and in particular the Primary FRCEM examination. The chapter outlines the key details of type 1 errors and type 2 errors. This chapter is laid out exactly following the RCEM syllabus, to allow easy reference and consolidation of learning.

THE EFFECTS OF L1–L2 PHONOLOGICAL MAPPINGS ON L2 PHONOLOGICAL SENSITIVITY

2020 ◽  
Vol 42 (5) ◽  
pp. 1041-1076
Author(s):  
Jeong-eun Kim ◽  
Yejin Cho ◽  
Youngsun Cho ◽  
Yeonjung Hong ◽  
Seohyun Kim ◽  
...  
Keyword(s):  
Response Times ◽  
Lower Sensitivity ◽  
English Sentence ◽  
Real Time Processing ◽  
Phonological Knowledge ◽  
Phonological Sensitivity ◽  
Type 2 Errors ◽  
English I

AbstractThis study examines the effects of asymmetrical mappings of L2 sounds to L1 sounds on real-time processing of L2 phonology. L1-Korean participants completed a self-paced listening (SPL) task paired with a picture verification (PV) task, in which an English sentence was presented word by word along with a picture that matched or mismatched the sentence. In the critical region, an L2 vowel was deliberately replaced with the wrong vowel for two types of English vowel pairs: Type 1: English vowel pairs showing a one-to-one mapping to Korean counterparts (e.g., English: /i/ and /æ/ to Korean /i/ and /æ/, respectively); and Type 2: English vowel pairs showing a two-to-one mapping to a Korean counterpart (e.g., English /i/ and /ɪ/ to Korean /i/). We analyzed response times (RTs) and PV accuracy. Longer RTs were observed for Type 1 errors than Type 2 errors, indicating lower sensitivity to L2 vowels with two-to-one mapping to an L1 vowel. Also, PV accuracy was lower for the sentences containing Type 2 errors. These results suggest that asymmetrical L2-L1 sound mapping can affect learners’ processing of L2 phonological knowledge, which in turn can negatively affect their comprehension.

The Termination of the 1997–98 El Niño. Part I: Mechanisms of Oceanic Change*

2006 ◽  
Vol 19 (12) ◽  
pp. 2633-2646 ◽  
Author(s):  
Gabriel A. Vecchi ◽  
D. E. Harrison
Keyword(s):  
El Niño ◽  
El Nino ◽  
Equatorial Pacific ◽  
Sea Surface ◽  
Central Pacific ◽  
Eastern Equatorial Pacific ◽  
Oceanic Response ◽  
Southward Shift ◽  
Sea Surface Temperature Anomalies ◽  
Subsurface Temperatures

Abstract The 1997–98 El Niño was both unusually strong and terminated unusually. Warm eastern equatorial Pacific (EEqP) sea surface temperature anomalies (SSTAs) exceeded 4°C at the event peak and lasted well into boreal spring of 1998, even though subsurface temperatures began cooling in December 1997. The oceanic processes that controlled this unusual termination are explored here and can be characterized by three features: (i) eastward propagating equatorial Pacific thermocline (Ztc) shoaling beginning in the central Pacific in November 1997; (ii) persistent warm EEqP SSTA between December 1997 and May 1998, despite strong EEqP Ztc shoaling (and subsurface cooling); and (iii) an abrupt cooling of EEqP SSTA in early May 1998 that exceeded 4°C within two weeks. It is shown here that these changes can be understood in terms of the oceanic response to changes to the meridional structure of the near-equatorial zonal wind field. Equatorial near-date-line westerly wind anomalies greatly decreased in late 1997, associated with a southward shift of convective and wind anomalies. In the EEqP, equatorial easterlies disappeared (reappeared) in late January (early May) 1998, driving the springtime extension (abrupt termination) of this El Niño event. The authors suggest that the wind changes arise from fundamentally meridional processes and are tied to the annual cycle of insolation.

Bioassessment of stream ecosystems enduring a decade of simulated degradation: lessons for the real world

2012 ◽  
Vol 69 (4) ◽  
pp. 784-796 ◽  
Author(s):  
Robert C. Bailey ◽  
Garry Scrimgeour ◽  
David Coté ◽  
Dan Kehler ◽  
Simon Linke ◽  
...  
Keyword(s):  
Suspended Sediments ◽  
Error Rates ◽  
Reference Condition ◽  
Benthic Macroinvertebrate ◽  
Taxon Richness ◽  
Macroinvertebrate Communities ◽  
Starting Condition ◽  
Type 2 Errors

The effects on benthic macroinvertebrate communities of simulated degradation of streams enabled evaluation of the effects of starting condition, type of degradation, and biota descriptor on the type 1 and type 2 error rates of bioassessment. Benthic macroinvertebrate communities from five reference streams in the Fraser River basin (British Columbia, Canada) were used as the starting conditions of replicated simulations of the effects of suspended sediments in three temporal patterns (none, one-time severe, constant moderate). The dynamics of the simulated stream communities and the type 1 and type 2 errors associated with bioassessments, as described by (i) taxon richness, (ii) EPT (Ephemeroptera, Plecoptera, Trichoptera) richness, (iii) proportion of EPT individuals in the community, (iv) difference in composition from the median reference community (MCDist), (v) Simpson’s diversity, and (vi) Simpson’s equitability, depended on the combination of starting condition, simpact treatment, and the biota descriptor. To reduce type 1 and type 2 errors in bioassessments using the reference condition approach, bioassessment programs should include (i) matching of test and expected reference communities and refinement of the definition of reference condition and (ii) several biota descriptors that include measures of richness, tolerance, and community composition.

STATISTICAL BRIEFING: TYPE 1 AND TYPE 2 ERRORS

2009 ◽  
Vol 50 (2) ◽  
pp. 239-239 ◽  
Author(s):  
CHRISTOPHER R. LAMB
Keyword(s):  
Type 2 Errors

scholarly journals A Three-Region Conceptual Model for Central Pacific El Niño Including Zonal Advective Feedback

2018 ◽  
Vol 31 (13) ◽  
pp. 4965-4979 ◽  
Author(s):  
Xiang-Hui Fang ◽  
Mu Mu
Keyword(s):  
Surface Temperature ◽  
Conceptual Model ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Equatorial Pacific ◽  
Sea Surface ◽  
Central Pacific ◽  
Central Pacific El Niño ◽  
Eastern Equatorial Pacific

The simple zonal two-region framework of the recharge paradigm can accurately manifest the traditional eastern Pacific (EP) type of El Niño–Southern Oscillation (ENSO), as its major warming center is located in the EP and the anomalous sea surface temperature (SST) changes monotonically from west to east along the equatorial Pacific. However, it cannot fully depict the variations of the central Pacific (CP) type of ENSO, whose major warming center is mainly situated in the CP. Therefore, to better investigate the characteristics of the CP type of ENSO, the recharge paradigm is extended to a three-region conceptual model to describe the entire western, central, and eastern equatorial Pacific. The results show that the extended conceptual model can depict the different variations between the CP and EP well. Specifically, with increasing magnitude of the zonal advective feedback over the CP (i.e., imitating the situation for CP ENSO), the period of the system and SST magnitude over the CP and EP both decrease. However, the decreasing amplitude is more intense over the EP, indicating an enlargement of the SST differences between the CP and EP. These results are all consistent with the observational characteristics of CP ENSO.

Sign in / Sign up

Export Citation Format

Share Document