Seasonal variability of the kinematic structure and rates of flow of currents in the north-western tropical Atlantic Ocean active layer

1997 ◽  
Vol 8 (6) ◽  
pp. 403-415
Author(s):  
G. F. Dzhiganshin ◽  
A. B. Polonsky
Keyword(s):  
Atlantic Ocean ◽  
Active Layer ◽  
Seasonal Variability ◽  
Tropical Atlantic ◽  
Kinematic Structure ◽  
Tropical Atlantic Ocean ◽  
The North ◽  
North Western

scholarly journals Obstacles and benefits of the implementation of a reduced-rank smoother with a high resolution model of the tropical Atlantic Ocean

Ocean Science ◽  
2012 ◽  
Vol 8 (5) ◽  
pp. 797-811
Author(s):  
N. Freychet ◽  
E. Cosme ◽  
P. Brasseur ◽  
J.-M. Brankart ◽  
E. Kpemlie
Keyword(s):  
Atlantic Ocean ◽  
Ocean Circulation ◽  
Three Dimensional ◽  
Circulation Model ◽  
Optimal Interpolation ◽  
Tropical Atlantic ◽  
Tropical Atlantic Ocean ◽  
The North ◽  
North Brazil ◽  
Resolution Model

Abstract. Most of oceanographic operational centers use three-dimensional data assimilation schemes to produce reanalyses. We investigate here the benefits of a smoother, i.e. a four-dimensional formulation of statistical assimilation. A square-root sequential smoother is implemented with a tropical Atlantic Ocean circulation model. A simple twin experiment is performed to investigate its benefits, compared to its corresponding filter. Despite model's non-linearities and the various approximations used for its implementation, the smoother leads to a better estimation of the ocean state, both on statistical (i.e. mean error level) and dynamical points of view, as expected from linear theory. Smoothed states are more in phase with the dynamics of the reference state, an aspect that is nicely illustrated with the chaotic dynamics of the North Brazil Current rings. We also show that the smoother efficiency is strongly related to the filter configuration. One of the main obstacles to implement the smoother is then to accurately estimate the error covariances of the filter. Considering this, benefits of the smoother are also investigated with a configuration close to situations that can be managed by operational center systems, where covariances matrices are fixed (optimal interpolation). We define here a simplified smoother scheme, called half-fixed basis smoother, that could be implemented with current reanalysis schemes. Its main assumption is to neglect the propagation of the error covariances matrix, what leads to strongly reduce the cost of assimilation. Results illustrate the ability of this smoother to provide a solution more consistent with the dynamics, compared to the filter. The smoother is also able to produce analyses independently of the observation frequency, so the smoothed solution appears more continuous in time, especially in case of a low frenquency observation network.

Polarising properties of the aerosols in the north-eastern tropical Atlantic Ocean, with emphasis on the ACE-2 period

Tellus B ◽  
2000 ◽  
Vol 52 (2) ◽  
pp. 620-635 ◽  
Author(s):  
Thierry Elias ◽  
Claude Devaux ◽  
Philippe Goloub ◽  
Maurice Herman
Keyword(s):  
Atlantic Ocean ◽  
Tropical Atlantic ◽  
Tropical Atlantic Ocean ◽  
The North ◽  
North Eastern

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.

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).

Polarising properties of the aerosols in the north-eastern tropical Atlantic Ocean, with emphasis on the ACE-2 period

Tellus B ◽  
2000 ◽  
Vol 52 (2) ◽  
pp. 620-635 ◽  
Author(s):  
Thierry Elisas ◽  
Claude Devaux ◽  
Philippe Goloub ◽  
Maurice Herman
Keyword(s):  
Atlantic Ocean ◽  
Tropical Atlantic ◽  
Tropical Atlantic Ocean ◽  
The North ◽  
North Eastern
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