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 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 Analysis of the Transport of Aerosols over the North Tropical Atlantic Ocean Using Time Series of POLDER/PARASOL Satellite Data

2020 ◽  
Vol 12 (5) ◽  
pp. 757
Author(s):  
Hélène Fréville ◽  
Malik Chami ◽  
Marc Mallet
Keyword(s):  
Time Series ◽  
Atlantic Ocean ◽  
Radiative Forcing ◽  
Regional Scale ◽  
Tropical Atlantic ◽  
Long Distance ◽  
Tropical Atlantic Ocean ◽  
The North ◽  
Coarse Mode ◽  
North Tropical Atlantic

The time series of total, fine and coarse POLAC/PARASOL aerosol optical depth (AOD) satellite products (2005–2013) processed by the POLAC algorithm are examined to investigate the transport of aerosols over the North Tropical Atlantic Ocean, a region that is characterized by significant dust aerosols events. First, the comparison of satellite observations with ground-based measurements acquired by AERONET ground-based measurements shows a satisfactory consistency for both total AOD and coarse mode AOD (i.e., correlation coefficients of 0.75 and bias ranging from −0.03 to 0.03), thus confirming the robustness and performance of POLAC/PARASOL data to investigate the spatio-temporal variability of the aerosols over the study area. Regarding fine mode aerosol, POLAC/PARASOL data present a lower performance with correlation coefficient ranging from 0.37 to 0.73. Second, the analysis of POLAC/PARASOL aerosol climatology reveals a high contribution of the coarse mode of aerosols ( AOD c between 0.1 and 0.4) at long distance from the African sources, confirming previous studies related to dust transport. The POLAC/PARASOL data were also compared with aerosol data obtained over the North Tropical Atlantic Ocean from MACC and MERRA-2 reanalyses. It is observed that the total AOD is underestimated in both reanalysis with a negative bias reaching −0.2. In summary, our results thus suggest that satellite POLAC/PARASOL observations of fine and coarse modes of aerosols could provide additional constraints useful to improve the quantification of the dust direct radiative forcing on a regional scale but also the biogeochemical processes such as nutrient supply to the surface waters.

Multi-site tropospheric ozone measurements across the North Tropical Atlantic during the summer of 2010

2013 ◽  
Vol 70 ◽  
pp. 131-148 ◽  
Author(s):  
Gregory S. Jenkins ◽  
Miliaritiana L. Robjhon ◽  
Belay Demoz ◽  
William R. Stockwell ◽  
Seydi A. Ndiaye ◽  
...  
Keyword(s):  
Tropospheric Ozone ◽  
Tropical Atlantic ◽  
The North ◽  
North Tropical Atlantic

scholarly journals Greenhouse warming intensifies north tropical Atlantic climate variability

2021 ◽  
Vol 7 (35) ◽  
pp. eabg9690
Author(s):  
Yun Yang ◽  
Lixin Wu ◽  
Ying Guo ◽  
Bolan Gan ◽  
Wenju Cai ◽  
...  
Keyword(s):  
Climate Variability ◽  
Southern Oscillation ◽  
Greenhouse Warming ◽  
Tropospheric Temperature ◽  
Tropical Atlantic ◽  
Moist Convection ◽  
Socioeconomic Impacts ◽  
The North ◽  
Sst Variability ◽  
North Tropical Atlantic

Variability of North Tropical Atlantic (NTA) sea surface temperature (SST), characterized by a near-uniform warming at its positive phase, is a consequential mode of climate variability. Modulated by El Niño–Southern Oscillation (ENSO) and the North Atlantic Oscillation, NTA warm anomalies tend to induce La Niña events, droughts in Northeast Brazil, increased frequency of extreme hurricanes, and phytoplankton blooms in the Guinea Dome. Future changes of NTA variability could have profound socioeconomic impacts yet remain unknown. Here, we reveal a robust intensification of NTA variability under greenhouse warming. This intensification mainly arises from strengthening of ENSO-forced Pacific-North American pattern and tropospheric temperature anomalies, as a consequence of an eastward shift of ENSO-induced equatorial Pacific convection and of increased ENSO variability, which enhances ENSO influence by reinforcing the associated wind and moist convection anomalies. The intensification of NTA SST variability suggests increased occurrences of extreme NTA events, with far-reaching ramifications.

scholarly journals Spurious North Tropical Atlantic pre-cursors to ENSO

2021 ◽  
Author(s):  
Wenjun Zhang ◽  
Feng Jiang ◽  
Malte Stuecker ◽  
Fei-Fei Jin ◽  
Axel Timmermann
Keyword(s):  
Cross Correlation ◽  
Southern Oscillation ◽  
Global Climate ◽  
Sea Surface ◽  
Time Varying ◽  
Tropical Atlantic ◽  
The North ◽  
Sst Variability ◽  
Primary Driver ◽  
North Tropical Atlantic

Abstract The 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 do not properly account for ENSO’s autocorrelation and the fact that the SST in the Atlantic and Pacific, as well as their atmospheric 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 fully consistent with a one-way Pacific to Atlantic forcing, even though the interpretation of lead-lag relationships may suggest otherwise.

New insight of the West Tropical Atlantic Circulation based on 25 years of satellite altimetry, PIRATA data and GLORYS ocean reanalysis

2021 ◽  
Author(s):  
Fabrice Hernandez ◽  
Djoirka M. Dimoune ◽  
Florence Birol ◽  
Fabien Leger ◽  
Moacyr Araujo
Keyword(s):  
Interannual Variability ◽  
Satellite Altimetry ◽  
Ocean Dynamics ◽  
Physical Parameters ◽  
Tropical Atlantic ◽  
The West ◽  
Ocean Reanalysis ◽  
The North ◽  
North Brazil ◽  
Basin Scale

<div><span>Satellite altimetry offers a mesoscale description of the ocean surface circulation worldwide since 1993. The Mercator Océan GLORYS12 reanalysis complement this description with a consistent 3-dimensional estimation of ocean physical parameters over the same period, with a reliability supported by the assimilation of available in-situ and satellite data. This information is used to revisit the ocean circulation description over the West Tropical Atlantic and in particular the seasonal and interannual variability of the western boundary current system from 20°S to 20°N connected to the tropical Atlantic basin scale circulation. PIRATA data since 2000 are used to validate the ocean reanalysis, and complement the description at depth of the main currents. The variability pattern and main characteristics of the North Brazil Undercurrent, the North Brazil Current and its Retroflection (NBCR), and the connections with the Equatorial Undercurrents, the South and North Equatorial Currents (SEC/NEC) and CounterCurrents (NECC) show seasonal changes. Both of their main pattern and the associated mesoscale field are dominated by the seasonal regimes. This circulation is linked to the tropical Atlantic Climate variability and the coupled pattern of wind and ocean dynamics. In particular, we show that the interannual variability of NECC, depending on the NBCR and SEC/NEC water transport exhibits different branches in relation with Tropical Atlantic Zonal and Meridional Mode of variability.</span></div>

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