Fading bioluminescence of the tropical Atlantic Ocean

North Africa is the world’s largest source of mineral dust, and this dust has potentially significant impacts on precipitation. Yet there is no consensus in published studies regarding the sign or magnitude of dust impacts on rainfall in either the highly climate-sensitive Sahel region of North Africa or the neighboring tropical Atlantic Ocean. Here the Geophysical Fluid Dynamics Laboratory (GFDL) Climate Model 2 (GFDL CM2.0) with Modular Ocean Model, version 4.1 (MOM4.1), run at coarse resolution (CM2Mc) is applied to investigate one poorly characterized aspect of dust–precipitation dynamics: the importance of sea surface temperature (SST) changes in mediating the atmospheric response to dust. Two model experiments were performed: one comparing Dust-On to Dust-Off simulations in the absence of ocean–atmosphere coupling, and the second comparing Dust-On to Dust-Off with the ocean fully coupled. Results indicate that SST changes in the coupled experiment reduce the magnitude of dust impacts on Sahel rainfall and flip the sign of the precipitation response over the nearby ocean. Over the Sahel, CM2Mc simulates a net positive impact of dust on monsoon season rainfall, but ocean–atmosphere coupling in the presence of dust decreases the inflow of water vapor, reducing the amount by which dust enhances rainfall. Over the tropical Atlantic Ocean, dust leads to SST cooling in the coupled experiment, resulting in increased static stability that overrides the warming-induced increase in convection observed in the uncoupled experiment and yields a net negative impact of dust on precipitation. These model results highlight the potential importance of SST changes in dust–precipitation dynamics in North Africa and neighboring regions.

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Climatology comparison and long-term variations of sea surface temperature over the tropical Atlantic Ocean

Journal of Geophysical Research Atmospheres ◽

10.1029/jc095ic06p09421 ◽

1990 ◽

Vol 95 (C6) ◽

pp. 9421 ◽

Cited By ~ 11

Author(s):

Jacques Servain ◽

Marc Séva ◽

Pierre Rual

Keyword(s):

Atlantic Ocean ◽

Surface Temperature ◽

Sea Surface Temperature ◽

Sea Surface ◽

Tropical Atlantic ◽

Tropical Atlantic Ocean ◽

Long Term Variations

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Impact of intraseasonal wind bursts on sea surface temperature variability in the far eastern tropical Atlantic Ocean during boreal spring 2005 and 2006: focus on the mid-May 2005 event

Ocean Science ◽

10.5194/os-14-849-2018 ◽

2018 ◽

Vol 14 (4) ◽

pp. 849-869 ◽

Cited By ~ 4

Author(s):

Gaëlle Herbert ◽

Bernard Bourlès

Keyword(s):

Atlantic Ocean ◽

Surface Temperature ◽

Kelvin Waves ◽

Sea Surface ◽

Tropical Atlantic ◽

Gulf Of Guinea ◽

Atmospheric Conditions ◽

Tropical Atlantic Ocean ◽

Boreal Spring ◽

Wind Bursts

Abstract. The impact of boreal spring intraseasonal wind bursts on sea surface temperature variability in the eastern tropical Atlantic Ocean in 2005 and 2006 is investigated using numerical simulation and observations. We especially focus on the coastal region east of 5° E and between the Equator and 7° S that has not been studied in detail so far. For both years, the southerly wind anomalies induced cooling episodes through (i) upwelling processes, (ii) vertical mixing due to the vertical shear of the current, and for some particular events (iii) a decrease in incoming surface shortwave radiation. The strength of the cooling episodes was modulated by subsurface conditions affected by the arrival of Kelvin waves from the west influencing the depth of the thermocline. Once impinging the eastern boundary, the Kelvin waves excited westward-propagating Rossby waves, which combined with the effect of enhanced westward surface currents contributed to the westward extension of the cold water. A particularly strong wind event occurred in mid-May 2005 and caused an anomalous strong cooling off Cape Lopez and in the whole eastern tropical Atlantic Ocean. From the analysis of oceanic and atmospheric conditions during this particular event, it appears that anomalously strong boreal spring wind strengthening associated with anomalously strong Hadley cell activity prematurely triggered the onset of coastal rainfall in the northern Gulf of Guinea, making it the earliest over the 1998–2008 period. No similar atmospheric conditions were observed in May over the 1998–2008 period. It is also found that the anomalous oceanic and atmospheric conditions associated with the event exerted a strong influence on rainfall off northeast Brazil. This study highlights the different processes through which the wind power from the South Atlantic is brought to the ocean in the Gulf of Guinea and emphasizes the need to further document and monitor the South Atlantic region.

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The barrier layer in the western tropical Atlantic Ocean

Geophysical Research Letters ◽

10.1029/1999gl900492 ◽

1999 ◽

Vol 26 (14) ◽

pp. 2069-2072 ◽

Cited By ~ 82

Author(s):

K. Pailler ◽

B. Bourlès ◽

Y. Gouriou

Keyword(s):

Atlantic Ocean ◽

Barrier Layer ◽

Tropical Atlantic ◽

Tropical Atlantic Ocean

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Multi-year satellite observations of instability waves in the Tropical Atlantic Ocean

Ocean Science Discussions ◽

10.5194/osd-2-1-2005 ◽

2005 ◽

Vol 2 (1) ◽

pp. 1-35 ◽

Cited By ~ 14

Author(s):

A. C. V. Caltabiano ◽

I. S. Robinson ◽

L. P. Pezzi

Keyword(s):

Atlantic Ocean ◽

Spectral Characteristics ◽

Coupling Mechanism ◽

Tropical Atlantic ◽

Atlantic Region ◽

Instability Waves ◽

Tropical Atlantic Ocean ◽

Zonal Winds ◽

Meridional Winds ◽

The Waves

Abstract. Instability waves in the tropical Atlantic Ocean are analysed by microwave satellite-based data spanning from 1998 to 2001. This is the first multi-year observational study of these waves in the region. Sea surface temperature (SST) data were used to show that the waves spectral characteristics vary from year-to-year. They also vary on each latitude north of the equator, with the region of 1° N, 15° W concentrating the largest variability when the time series is averaged along the years. Analyses of wind components show that meridional winds are more affected near the equator and 1° N, while zonal winds are more affected further north at around 3° N and 4° N. Concurrent observations of SST, wind, atmospheric water vapour, liquid cloud water, precipitation rates and wind were used to demonstrate the possible influence of these waves on the Intertropical Convergence Zone (ITCZ). It seems that these instabilities have a large impact on the ITCZ due to its proximity of the equator, compared to its Pacific counterpart, and the geography of the tropical Atlantic basin. These analyses also suggest that the air-sea coupling mechanism suggested by Wallace can also be applied to the tropical Atlantic region.

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