scholarly journals On forecasting abnormal climatic events in the tropical Atlantic Ocean

1995 ◽  
Vol 13 (9) ◽  
pp. 995-1008 ◽  
Author(s):  
J. Servain ◽  
S. Arnault
Keyword(s):  
Atlantic Ocean ◽  
Wind Stress ◽  
Linear Method ◽  
Ocean Model ◽  
Height Anomaly ◽  
Boreal Summer ◽  
Tropical Atlantic ◽  
Gulf Of Guinea ◽  
Dynamic Height ◽  
Tropical Atlantic Ocean

Abstract. Modelling and observational evidence indicate that interannual variabilities of dynamic height and sea surface temperature (SST) in the eastern part of the tropical Atlantic Ocean (Gulf of Guinea) are largely induced by preceding fluctuations in wind stress, mainly in the western equatorial basin. A wind-driven linear ocean model is used here to test the possibility of forecasting the abnormal dynamic heights. A control run of the model, forced by 1964–1993 wind stress monthly means, is first conducted. Yearly test runs (1964–1994) are subsequently performed from January to August by forcing the model with observed winds from January to May, and then by forcing with the May wind assumed to persist from June to August. During the last three decades the largest deviations of dynamic height simulated by the control run in the Gulf of Guinea in boreal summer would have been correctly forecast from wind data related only to conditions in May of each year. However, for weak climatic anomalies, the model may forecast overestimated values. For the most part (about 20 times during the last 30 years), the sign of the observed SST anomaly in the centre of the Gulf of Guinea during the boreal summer is identical to the sign of simulated anomalies of dynamic height deduced from both control and test runs. Along the eastern equatorial waveguide, the sea level forecasting skill slowly decreases from the first 2 weeks of June until the second 2 weeks of August, but remains high on both sides of the equator throughout boreal summer, as is expected from the adjustment in a linear ocean model. It is established that throughout the year in the Gulf of Guinea the accuracy of the 1-month forecast dynamic height anomaly provided by the simple linear method is greater than that of the 1-month forecast assuming persistence.

scholarly journals 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 ◽  
2018 ◽  
Vol 14 (4) ◽  
pp. 849-869 ◽  
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.

scholarly journals African biomass burning is a substantial source of phosphorus deposition to the Amazon, Tropical Atlantic Ocean, and Southern Ocean

2019 ◽  
Vol 116 (33) ◽  
pp. 16216-16221 ◽  
Author(s):  
Anne E. Barkley ◽  
Joseph M. Prospero ◽  
Natalie Mahowald ◽  
Douglas S. Hamilton ◽  
Kimberly J. Popendorf ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
Biomass Burning ◽  
Amazon Basin ◽  
Transport Model ◽  
Boreal Summer ◽  
Tropical Atlantic ◽  
Dust Transport ◽  
Tropical Atlantic Ocean ◽  
African Dust ◽  
Soluble P

The deposition of phosphorus (P) from African dust is believed to play an important role in bolstering primary productivity in the Amazon Basin and Tropical Atlantic Ocean (TAO), leading to sequestration of carbon dioxide. However, there are few measurements of African dust in South America that can robustly test this hypothesis and even fewer measurements of soluble P, which is readily available for stimulating primary production in the ocean. To test this hypothesis, we measured total and soluble P in long-range transported aerosols collected in Cayenne, French Guiana, a TAO coastal site located at the northeastern edge of the Amazon. Our measurements confirm that in boreal spring when African dust transport is greatest, dust supplies the majority of P, of which 5% is soluble. In boreal fall, when dust transport is at an annual minimum, we measured unexpectedly high concentrations of soluble P, which we show is associated with the transport of biomass burning (BB) from southern Africa. Integrating our results into a chemical transport model, we show that African BB supplies up to half of the P deposited annually to the Amazon from transported African aerosol. This observational study links P-rich BB aerosols from Africa to enhanced P deposition in the Amazon. Contrary to current thought, we also show that African BB is a more important source of soluble P than dust to the TAO and oceans in the Southern Hemisphere and may be more important for marine productivity, particularly in boreal summer and fall.

Mean and Variability of the Tropical Atlantic Ocean in the CCSM4*

2012 ◽  
Vol 25 (14) ◽  
pp. 4860-4882 ◽  
Author(s):  
Ernesto Muñoz ◽  
Wilbert Weijer ◽  
Semyon A. Grodsky ◽  
Susan C. Bates ◽  
Ilana Wainer
Keyword(s):  
Atlantic Ocean ◽  
Wind Stress ◽  
Heat Budget ◽  
South Atlantic ◽  
Tropical Atlantic ◽  
Climate System Model ◽  
Tropical Atlantic Ocean ◽  
Modes Of Variability ◽  
Sst Variability ◽  
Budget Analysis

Abstract This study analyzes important aspects of the tropical Atlantic Ocean from simulations of the fourth version of the Community Climate System Model (CCSM4): the mean sea surface temperature (SST) and wind stress, the Atlantic warm pools, the principal modes of SST variability, and the heat budget in the Benguela region. The main goal was to assess the similarities and differences between the CCSM4 simulations and observations. The results indicate that the tropical Atlantic overall is realistic in CCSM4. However, there are still significant biases in the CCSM4 Atlantic SSTs, with a colder tropical North Atlantic and a hotter tropical South Atlantic, that are related to biases in the wind stress. These are also reflected in the Atlantic warm pools in April and September, with its volume greater than in observations in April and smaller than in observations in September. The variability of SSTs in the tropical Atlantic is well represented in CCSM4. However, in the equatorial and tropical South Atlantic regions, CCSM4 has two distinct modes of variability, in contrast to observed behavior. A model heat budget analysis of the Benguela region indicates that the variability of the upper-ocean temperature is dominated by vertical advection, followed by meridional advection.

scholarly journals Impact of intraseasonal wind bursts on SST variability in the far eastern Tropical Atlantic Ocean during boreal spring 2005 and 2006. Focus on the mid-May 2005 event

2017 ◽  
Author(s):  
Gaëlle Herbert ◽  
Bernard Bourlès
Keyword(s):  
Atlantic Ocean ◽  
South Atlantic ◽  
Kelvin Waves ◽  
Hadley Cell ◽  
Strong Wind ◽  
Tropical Atlantic ◽  
Gulf Of Guinea ◽  
Atmospheric Conditions ◽  
Tropical Atlantic Ocean ◽  
Wind Bursts

Abstract. The impact of 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 specially focus on the few documented coastal region east of 5° E and between the equator and 7° S. For both years, the southerly winds strengthening induced cooling events through i) upwelling processes; ii) vertical mixing due to vertical shear of zonal current; and for some particular events iii) a decrease of incoming surface shortwave radiation. The strength of the cooling events 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 anomalous strong spring wind strengthening associated to anomalous strong Hadley cell activity made the event as a decisive event which prematurely triggered the rainfall coastal onset in the northern Gulf of Guinea. Results show that no similar atmospheric conditions were observed over the 1998–2008 period. It is also found that the anomalous oceanic and atmospheric conditions associated to the event exerted strong influence on rainfall off Northeast Brazil. This study highlights the different processes through which the wind power from 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.

scholarly journals Correction to: Weakened SST variability in the tropical Atlantic Ocean since 2000

2021 ◽  
Author(s):  
Arthur Prigent ◽  
Joke F. Lübbecke ◽  
Tobias Bayr ◽  
Mojib Latif ◽  
Christian Wengel
Keyword(s):  
Atlantic Ocean ◽  
Tropical Atlantic ◽  
Tropical Atlantic Ocean ◽  
Sst Variability

scholarly journals Simulated Dust Aerosol Impacts on Western Sahelian Rainfall: Importance of Ocean Coupling

2018 ◽  
Vol 31 (22) ◽  
pp. 9107-9124 ◽  
Author(s):  
Asha K. Jordan ◽  
Anand Gnanadesikan ◽  
Benjamin Zaitchik
Keyword(s):  
Atlantic Ocean ◽  
North Africa ◽  
Negative Impact ◽  
Positive Impact ◽  
Geophysical Fluid Dynamics Laboratory ◽  
Tropical Atlantic ◽  
Tropical Atlantic Ocean ◽  
Ocean Atmosphere ◽  
Sahel Region ◽  
Dust Precipitation

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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