scholarly journals Two distinct roles of Atlantic SSTs in ENSO variability: North Tropical Atlantic SST and Atlantic Niño

2013 ◽  
Vol 40 (15) ◽  
pp. 4012-4017 ◽  
Author(s):  
Yoo-Geun Ham ◽  
Jong-Seong Kug ◽  
Jong-Yeon Park
Keyword(s):  
Tropical Atlantic ◽  
Enso Variability ◽  
North Tropical Atlantic ◽  
Atlantic Niño

scholarly journals Spurious North Tropical Atlantic precursors to El Niño

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Wenjun Zhang ◽  
Feng Jiang ◽  
Malte F. Stuecker ◽  
Fei-Fei Jin ◽  
Axel Timmermann
Keyword(s):  
El Niño ◽  
Cross Correlation ◽  
El Nino ◽  
Southern Oscillation ◽  
Global Climate ◽  
Tropical Atlantic ◽  
The North ◽  
Sst Variability ◽  
Primary Driver ◽  
North Tropical Atlantic

AbstractThe El Niño-Southern Oscillation (ENSO), the primary driver of year-to-year global climate variability, is known to influence the North Tropical Atlantic (NTA) sea surface temperature (SST), especially during boreal spring season. Focusing on statistical lead-lag relationships, previous studies have proposed that interannual NTA SST variability can also feed back on ENSO in a predictable manner. However, these studies did not properly account for ENSO’s autocorrelation and the fact that the SST in the Atlantic and Pacific, as well as their interaction are seasonally modulated. This can lead to misinterpretations of causality and the spurious identification of Atlantic precursors for ENSO. Revisiting this issue under consideration of seasonality, time-varying ENSO frequency, and greenhouse warming, we demonstrate that the cross-correlation characteristics between NTA SST and ENSO, are consistent with a one-way Pacific to Atlantic forcing, even though the interpretation of lead-lag relationships may suggest otherwise.

Interannual sea surface chlorophyll-a signature in the tropical Atlantic

2021 ◽  
Author(s):  
Fanny Chenillat ◽  
Julien Jouanno ◽  
Serena Illig ◽  
Founi Mesmin Awo ◽  
Gaël Alory ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Sea Surface ◽  
Tropical Atlantic ◽  
Cold Tongue ◽  
Equatorial Atlantic ◽  
Atlantic Region ◽  
The North ◽  
Sst Anomaly ◽  
Equatorial Band ◽  
North Tropical Atlantic

<div><span>Surface chlorophyll-<em>a </em>concentration (CHL-<em>a</em>) remotely observed by satellite shows a marked seasonal and interannual variability in the Tropical Atlantic, with potential consequences on the marine trophic web. Seasonal and interannual CHL-<em>a </em>variability peaks in boreal summer and shows maxima in the equatorial Atlantic region at 10˚W, spreading from 0 to 30˚W. In this study, we analyze how the remotely-sensed surface CHL-<em>a </em>responds to the leading climate modes affecting the interannual equatorial Atlantic variability over the 1998-2018 period, namely the Atlantic Zonal Mode (AZM) and the North Tropical Atlantic Mode (NTA, also known as the Atlantic Meridional Mode). The AZM is characterized by anomalous warming (or cooling) along the eastern equatorial band. In contrast, the NTA is characterized by an interhemispheric pattern of the sea surface temperature (SST), with anomalous warm (cold) conditions in the north tropical Atlantic region and weak negative (positive) SST anomalies south of the equator. We show that both modes significantly drive the interannual Tropical Atlantic surface CHL-<em>a </em>variability, with different timings and contrasted modulation on the eastern and western portions of the cold tongue area. Our results also reveal that the NTA slightly dominates (40%) the summer tropical Atlantic interannual variability over the last two decades, most probably because of a positive phase of the Atlantic multidecadal oscillation. For each mode of variability, we analyze an event characterized by an extreme negative sea surface temperature (SST) anomaly in the Atlantic equatorial band. Both modes are associated with a positive CHL-<em>a </em>anomaly at the equator. In 2002, a negative phase of the NTA led to cold SST anomaly and high positive CHL-<em>a </em>in the western portion of the cold tongue, peaking in June-July and lasting until the end of the year. In contrast, in 2005, a negative phase of the AZM drove cool temperature and positive CHL-<em>a </em>in the eastern equatorial band, with a peak in May-June and almost no signature after August. Such contrasted year to year conditions can affect the marine ecosystem by changing temporal and spatial trophic niches for pelagic predators, thus inducing significant variations for ecosystem functioning and fisheries.</span></div>

scholarly journals North Tropical Atlantic influence on western Amazon fire season variability

2011 ◽  
Vol 38 (12) ◽  
pp. n/a-n/a ◽  
Author(s):  
Katia Fernandes ◽  
Walter Baethgen ◽  
Sergio Bernardes ◽  
Ruth DeFries ◽  
David G. DeWitt ◽  
...  
Keyword(s):  
Fire Season ◽  
Tropical Atlantic ◽  
North Tropical Atlantic

scholarly journals SST Indexes in the Tropical South Atlantic for Forecasting Rainy Seasons in Northeast Brazil

Atmosphere ◽  
2019 ◽  
Vol 10 (6) ◽  
pp. 335 ◽  
Author(s):  
Gbèkpo Aubains Hounsou-Gbo ◽  
Jacques Servain ◽  
Moacyr Araujo ◽  
Guy Caniaux ◽  
Bernard Bourlès ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Positive Relationship ◽  
South Atlantic ◽  
Sea Surface ◽  
Boreal Summer ◽  
Northeast Brazil ◽  
Tropical Atlantic ◽  
Rainfall Anomalies ◽  
Atlantic Niño

May-to-July and February-to-April represent peak rainy seasons in two sub-regions of Northeast Brazil (NEB): Eastern NEB and Northern NEB respectively. In this paper, we identify key oceanic indexes in the tropical South Atlantic for driving these two rainy seasons. In Eastern NEB, the May-to-July rainfall anomalies present a positive relationship with the previous boreal winter sea surface temperature anomalies (SSTA) in the southeast tropical Atlantic (20°–10° S; 10° W–5° E). This positive relationship, which spread westward along the southern branch of the South Equatorial Current, is associated with northwesterly surface wind anomalies. A warmer sea surface temperature in the southwestern Atlantic warm pool increases the moisture flux convergence, as well as its ascending motion and, hence, the rainfall along the adjacent coastal region. For the Northern NEB, another positive relationship is observed between the February-to-April rainfall anomalies and the SSTA of the previous boreal summer in the Atlantic Niño region (3° S–3° N; 20° W–0°). The negative remote relationship noticeable between the Northern NEB rainfall and the concomitant Pacific Niño/Niña follows cold/warm events occurring during the previous boreal summer in the eastern equatorial Atlantic. The southeastern tropical Atlantic and Atlantic Niño SSTA indexes may, then, be useful to predict seasonal rainfall over the Eastern and Northern NEB, respectively, for about a 6 month leading period. The ability of both southeastern tropical Atlantic and Atlantic Niño SSTA indexes to forecast the Eastern and Northern NEB rainfall, with about a 6 month lead time, is improved when these indexes are respectively combined with the Niño3 (5° S–5° N; 150°–90° W) and the northeast subtropical Atlantic (20° N–35° N, 45° W–20° W), mainly from the 1970’s climate shift.

scholarly journals Extratropical Atmospheric Response to the Atlantic Niño Decaying Phase

2011 ◽  
Vol 24 (6) ◽  
pp. 1613-1625 ◽  
Author(s):  
Javier García-Serrano ◽  
Teresa Losada ◽  
Belén Rodríguez-Fonseca
Keyword(s):  
Los Angeles ◽  
Wave Train ◽  
Northeastern Brazil ◽  
Boreal Summer ◽  
Atmospheric Response ◽  
Tropical Atlantic ◽  
Thermal Forcing ◽  
Sensitivity Experiment ◽  
Important Conclusion ◽  
Atlantic Niño

Abstract The Atlantic Niño or Atlantic Equatorial Mode (EM) is the dominant coupled variability phenomenon in the tropical Atlantic basin during boreal summer. From the 1970s, the mode has changed, evolving in time from east to west and without persisting until the following winter. In a previous observational work, the authors have studied the atmospheric response to the EM during the 1979–2005 period, proposing three main issues along the decaying phase of this mode: 1) the continuous confinement of the anomalous deep convection over northeastern Brazil following the thermal-forcing decay; 2) an increasing dipole-like precipitation anomaly with dry conditions in the Florida–Gulf of Mexico region; and 3) the excitation of Rossby waves forced by the remaining upper-tropospheric divergence that are trapped into the subtropical jet but do not show a robust impact on the European sector. In this work, a 10-member ensemble simulation for the recent EM with the University of California, Los Angeles AGCM model has been analyzed for assessing the evolution of the atmospheric response to the summer Atlantic Niño decay. Results from the sensitivity experiment support that the former and the latter findings can be interpreted in terms of the Atlantic thermal forcing; while the negative rainfall anomalies in the western subtropical basin require an external forcing outside the tropical Atlantic. Prior studies point at the peaking Pacific El Niño as a potential player. An important conclusion of this work is that the seasonal atmospheric response to the Atlantic Niño decaying phase is mainly determined by the climatological jet stream’s position and intensity. In this way, this response shows an arching pattern over the North Atlantic region during summer–autumn and a zonally oriented wave train during autumn–winter.

scholarly journals Interannual variability of the tropical Atlantic independent of and associated with ENSO: Part I. The North Tropical Atlantic

2006 ◽  
Vol 26 (14) ◽  
pp. 1937-1956 ◽  
Author(s):  
Itsuki C. Handoh ◽  
Adrian J. Matthews ◽  
Grant R. Bigg ◽  
David P. Stevens
Keyword(s):  
Interannual Variability ◽  
Tropical Atlantic ◽  
The North ◽  
North Tropical Atlantic

scholarly journals Understanding the 2017 warm event in North Tropical Atlantic

2020 ◽  
Author(s):  
Ana Trindade ◽  
Marta Matín-Rey ◽  
Marcos Portabella ◽  
Eleftheria Exarchou ◽  
Pablo Ortega ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Large Scale ◽  
Temporal Frequency ◽  
Surface Wind ◽  
Sea Surface ◽  
Earth Model ◽  
Tropical Atlantic ◽  
Ocean Wind ◽  
North Tropical Atlantic

<p>The Atlantic Ocean has suffered tremendous warming during recent decades as a consequence of anthropogenic forcing, modulated by the natural low frequency variability. Special attention should be paid to the high temporal frequency of warm interannual events in the North Tropical Atlantic (NTA) since the early 2000s, resulting in the most intense hurricane seasons on record (Hallam et al., 2017; Lim et al., 2018; Murakami et al., 2018; Klotzbach et al., 2018; Camp et al., 2018). Moreover, NTA sea surface temperature anomalies during boreal spring have been suggested as a potential precursor to the Equatorial Mode (Foltz and McPhaden, 2010ab; Burmeister et al., 2016; Martín-Rey and Lazar, 2019; Martín-Rey et al., 2019).<strong> </strong></p><p>This study aims to investigate the development of the 2017 NTA spring-summer warming event, which was the strongest of the last decade, as well as the importance of an accurate ocean forcingin the simulation of this event. For such purpose, a set of four simulations using distinct ocean wind forcing products, namely from the EC-Earth model, ERA-Interim (ERAi) reanalysis and a new ERAi-corrected ocean wind product (ERAstar), have been performed and analysed.The latter consists of average geolocated scatterometer-based corrections applied to ERAi output (Trindade et al., 2019).In this sense, ERAstar includes some of the physical processes missing or misrepresented by ERA-i, and corrects for large-scale NWP parameterization and dynamical errors.</p><p>The air-sea processes underlying the onset and development of the warm 2017 NTA event and the wave activity present in the equatorial Atlantic will be explored to determine their possible connection with the equatorial sea surface temperature variability. Furthermore, the comparison between the different experiments allows us to validate the new surface wind dataset and evaluate the importance of accurate, high-resolution ocean forcing in the representation of tropical Atlantic variability.</p>

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