scholarly journals The Predictive Skill and the Most Predictable Pattern in the Tropical Atlantic: The Effect of ENSO

2007 ◽  
Vol 135 (5) ◽  
pp. 1786-1806 ◽  
Author(s):  
Zeng-Zhen Hu ◽  
Bohua Huang
Keyword(s):  
South America ◽  
Atlantic Ocean ◽  
North Atlantic ◽  
Lead Time ◽  
Tropical Atlantic ◽  
Tropical Atlantic Ocean ◽  
Predictive Skill ◽  
Tropical North Atlantic ◽  
Predictable Pattern ◽  
Most Predictable Patterns

Abstract This work investigates the predictive skill and most predictable pattern in the NCEP Climate Forecast System (CFS) in the tropical Atlantic Ocean. The skill is measured by the sea surface temperature (SST) anomaly correlation between the predictions and the corresponding analyses, and the most predictable patterns are isolated by an empirical orthogonal function analysis with a maximized signal-to-noise ratio. On average, for predictions with initial conditions (ICs) of all months, the predictability of SST is higher in the west than in the east. The highest skill is near the tropical Brazilian coast and in the Caribbean Sea, and the lowest skill occurs in the eastern coast. Seasonally, the skill is higher for predictions with ICs in summer or autumn and lower for those with ICs in spring. The CFS poorly predicts the meridional gradient in the tropical Atlantic Ocean. The superiority of the CFS predictions to the persistence forecasts depends on IC month, region, and lead time. The CFS prediction is generally better than the corresponding persistence forecast when the lead time is longer than 3 months. The most predictable pattern of SST in March has the same sign in almost the whole tropical Atlantic. The corresponding pattern in March is dominated by the same sign for geopotential height at 200 hPa in most of the domain and by significant opposite variation for precipitation between the northwestern tropical North Atlantic and the regions from tropical South America to the southwestern tropical North Atlantic. These predictable signals mainly result from the influence of the El Niño–Southern Oscillation (ENSO). The significant values in the most predictable pattern of precipitation in the regions from tropical South America to the southwestern tropical North Atlantic in March are associated with excessive divergence (convergence) at low (high) levels over these regions in the CFS. For the CFS, the predictive skill in the tropical Atlantic Ocean is largely determined by its ability to predict ENSO. This is due to the strong connection between ENSO and the most predictable patterns in the tropical Atlantic Ocean in the model. The higher predictive skill of tropical North Atlantic SST is consistent with the ability of the CFS to predict ENSO on interseasonal time scales, particularly for the ICs in warm months from March to October. In the southeastern ocean, the systematic warm bias is a crucial factor leading to the low skill in this region.

scholarly journals Post-Bomb Radiocarbon Records of Surface Corals from the Tropical Atlantic Ocean

Radiocarbon ◽  
1996 ◽  
Vol 38 (3) ◽  
pp. 563-572 ◽  
Author(s):  
Ellen R. M. Druffel
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
Water Mass ◽  
Cape Verde ◽  
North Equatorial Current ◽  
Tropical Atlantic ◽  
Tropical Ocean ◽  
Tropical Atlantic Ocean ◽  
Renewal Rate ◽  
The North

Δ14C records are reported for post-bomb corals from three sites in the tropical Atlantic Ocean. In corals from 18°S in the Brazil Current, Δ14C values increased from ca. −58% in the early 1950s to +138% by 1974, then decreased to 110‰ by 1982. Shorter records from 8ºS off Brazil and from the Cape Verde Islands (17°N) showed initially higher Δ14C values before 1965 than those at 18ºS, but showed lower rates of increase of Δ14C during the early 1960s. There is general agreement between the coral results and Δ14C of dissolved inorganic carbon (DIC) measured in seawater previously for locations in the tropical Atlantic Ocean. Δ14C values at our tropical ocean sites increased at a slower rate than those observed previously in the temperate North Atlantic (Florida and Bermuda), owing to the latter's proximity to the bomb 14C input source in the northern, hemisphere. Model results show that from 1960–1980 the Cape Verde coral and selected DIG Δ14C values from the North Equatorial Current agree with that calculated for the North Atlantic based on an isopycnal mixing model with a constant water mass renewal rate between surface and subsurface waters. This is in contrast to Δ14C values in Bermuda corals that showed higher post-bomb values than those predicted using a constant water mass renewal rate, hence indicating that ventilation in the western north Atlantic Ocean had decreased by a factor of 3 during the 1960s and 1970s (Druffel 1989).

scholarly journals Space-borne observations link the tropical Atlantic ozone maximum and paradox to lightning

2003 ◽  
Vol 3 (6) ◽  
pp. 5725-5754 ◽  
Author(s):  
G. S. Jenkins ◽  
J.-H. Ryu
Keyword(s):  
South America ◽  
West Africa ◽  
Atlantic Ocean ◽  
Biomass Burning ◽  
Central Africa ◽  
Tropical Atlantic ◽  
Tropical Atlantic Ocean ◽  
The North ◽  
June July ◽  
Column Ozone

Abstract. The causes of high tropospheric column ozone values over the Tropical Atlantic Ocean during September, October, and November (SON) are investigated by examining lightning during 1998–2001. The cause for high tropospheric column ozone in the hemisphere opposite of biomass burning (tropical ozone paradox) is also examined. Our results show that lightning is central to high tropospheric column ozone during SON and responsible for the tropical ozone paradox during December, January, and February (DJF) and June, July and August (JJA). During SON large numbers of flashes are observed in South America, Central and West Africa enriching the tropospheric column ozone over the Tropical Atlantic Ocean. During JJA the largest numbers of lightning flashes are observed in West Africa, enriching tropospheric column ozone to the north of 5° S in the absence biomass burning. During DJF, lightning is concentrated in South America and Central Africa enriching tropospheric column ozone south of the Equator in the absence of biomass burning.

Water Masses Chemical Properties in the Western Tropical Atlantic Ocean

2021 ◽  
Author(s):  
Renan Luis Evangelista Vieira ◽  
Leticia Cotrim da Cunha ◽  
Ricardo de Almeida Keim ◽  
Carlos Augusto Musetti de Assis ◽  
Jessica da Silva Nogueira ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
Nutrient Concentration ◽  
Chemical Properties ◽  
Intertropical Convergence Zone ◽  
Water Masses ◽  
Nutrient Concentrations ◽  
Convergence Zone ◽  
Tropical Atlantic ◽  
Tropical Atlantic Ocean

<p>Here we characterize the chemical properties of the water masses in the Western Tropical Atlantic Ocean according to their inorganic nutrient concentration: dissolved inorganic nitrogen (DIN), phosphate and silicate. We collected full-depth water samples from 16 oceanographic stations along the 38°W transect, from 1°S to 15°N during the PIRATA-BR XVIII cruise, in October-November 2018. In this region, the surface and subsurface circulation in the Atlantic Ocean displays complex seasonal patterns, under influence of the Intertropical Convergence Zone. The samples were collected from Niskin bottles closed in ten different depths, stored frozen, and later analysed through spectrophotometry. Besides that, the CTD-O<sub>2</sub> data provided continuous salinity, temperature, and dissolved oxygen measurements, used to identify the water masses according to their thermohaline indexes. Six water masses were identified in the region based on their neutral density limits: Tropical Surface Water (TSW, γ<sup>n</sup> < 24.448 kg m<sup>-3</sup>); South and North Atlantic Central Water (SACW and NACW, γ<sup>n</sup> 24.448 – 26.815 kg m<sup>-3</sup>); Antarctic Intermediate Water (AAIW, γ<sup>n</sup> 26.815 – 27.7153 kg m<sup>-3</sup>); North Atlantic Deep Water (NADW, γ<sup>n</sup> 27.7153 – 28.135 kg m<sup>-3</sup>); and Antarctic Bottom Water (AABW, γ<sup>n</sup> > 28.135 kg m<sup>-3</sup>).  The oligotrophic TSW is almost completely depleted in nutrients; Central Waters NACW and SACW have the following concentration ranges: DIN, 5 – 15 µmol/kg, phosphate, 0.5 – 1.0 µmol/kg, silicate, 5 – 20 µmol/kg); AAIW nutrient concentrations are DIN: 30 – 40 µmol/kg, phosphate: 1.5 – 2.5 µmol/kg, and silicate: 25 – 40 µmol/kg; NADW nutrient concentrations are DIN: 15 – 25 µmol/kg, phosphate: 1.0 – 1.5 µmol/kg) , and silicate: 20 – 45 µmol/kg; and AABW nutrient concentration ranges are: 40 – 80 µmol/kg silicate, 30 – 35 µmol/kg DIN, and 1.5 – 2.5 µmol/kg phosphate. North of 5°N up to 15°N, there is a region of lower oxygen and higher phosphate concentrations, comprising the central water and the upper AAIW layers, extending from 200 m to 800 m. This corresponds to the area under influence of the eastward flowing North Equatorial Counter Current (NECC) and North Equatorial Under Current (NEUC), which are both, in turn, influenced by the position of the Intertropical Convergence Zone (ITCZ). Further study directions include a detailed study of the multiple source waters to this central layer, associated to the regional circulation, and possible linking to the eastern tropical Atlantic oxygen minimum zone.</p>

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.

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 A quest for the biological sources of long chain alkyl diols in the western tropical North Atlantic Ocean

2018 ◽  
Vol 15 (19) ◽  
pp. 5951-5968 ◽  
Author(s):  
Sergio Balzano ◽  
Julie Lattaud ◽  
Laura Villanueva ◽  
Sebastiaan W. Rampen ◽  
Corina P. D. Brussaard ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
Water Column ◽  
North Atlantic ◽  
18S Rrna ◽  
North Atlantic Ocean ◽  
18S Rrna Gene ◽  
Rrna Gene ◽  
Tropical North Atlantic ◽  
Biological Sources ◽  
Long Chain

Abstract. Long chain alkyl diols (LCDs) are widespread in the marine water column and sediments, but their biological sources are mostly unknown. Here we combine lipid analyses with 18S rRNA gene amplicon sequencing on suspended particulate matter (SPM) collected in the photic zone of the western tropical North Atlantic Ocean at 24 stations to infer relationships between LCDs and potential LCD producers. The C30 1,15-diol was detected in all SPM samples and accounted for >95 % of the total LCDs, while minor proportions of C28 and C30 1,13-diols, C28 and C30 1,14-diols, as well as C32 1,15-diol were found. The concentration of the C30 and C32 diols was higher in the mixed layer of the water column compared to the deep chlorophyll maximum (DCM), whereas concentrations of C28 diols were comparable. Sequencing analyses revealed extremely low contributions (≈0.1 % of the 18S rRNA gene reads) of known LCD producers, but the contributions from two taxonomic classes with which known producers are affiliated, i.e. Dictyochophyceae and Chrysophyceae, followed a trend similar to that of the concentrations of C30 and C32 diols. Statistical analyses indicated that the abundance of 4 operational taxonomic units (OTUs) of the Chrysophyceae and Dictyochophyceae, along with 23 OTUs falling into other phylogenetic groups, were weakly (r≤0.6) but significantly (p value <0.01) correlated with C30 diol concentrations. It is not clear whether some of these OTUs might indeed correspond to C28−32 diol producers or whether these correlations are just indirect and the occurrence of C30 diols and specific OTUs in the same samples might be driven by other environmental conditions. Moreover, primer mismatches were unlikely, but cannot be excluded, and the variable number of rRNA gene copies within eukaryotes might have affected the analyses leading to LCD producers being undetected or undersampled. Furthermore, based on the average LCD content measured in cultivated LCD-producing algae, the detected concentrations of LCDs in SPM are too high to be explained by the abundances of the suspected LCD-producing OTUs. This is likely explained by the slower degradation of LCDs compared to DNA in the oxic water column and suggests that some of the LCDs found here were likely to be associated with suspended debris, while the DNA from the related LCD producers had been already fully degraded. This suggests that care should be taken in constraining biological sources of relatively stable biomarker lipids by quantitative comparisons of DNA and lipid abundances.

Sign in / Sign up

Export Citation Format

Share Document