The region south of South Africa, encompassing the Agulhas Current and Retroflection, and part of the Southern Ocean, is known for its severe meteorological conditions. Because of these conditions, ...in-situ observations are rare. Consequently, remote-sensing satellite observations and high-resolution regional weather forecasts at the ocean surface are difficult to assess. However, atmospheric data collected in the southern hemisphere summer of 2008 during the International Polar Year-BONUS-GoodHope campaign were used to validate two satellite data sets: the twice daily QuikSCAT winds and the daily OAflux data set of latent and sensible heat fluxes. The surface winds and heat fluxes forecasts produced by a regional atmospheric model were also assessed along the ship track. In this study, we have shown that the two data sets exhibited a very good accordance with daily in-situ observations. During the campaign, the correlation coefficients for wind speed and direction were 0.97 and 0.91, respectively, and those for latent and sensible heat fluxes were 0.92 and 0.90, respectively. The QuikSCAT wind speed was underestimated by 1.37 m/s relative to in-situ data, south of the Subtropical Front. Large differences in heat fluxes in both OAflux and the atmospheric model were observed when crossing the Subtropical Front and a warm eddy, as well as during a storm, when gale force winds reached more than 20 m/s. The two data sets were then used to assess the regional model forecasts over a larger area south of South Africa, not limited to the ship track. Most of the model errors were located in a region north of the Subtropical Front, where the sea surface temperature used by the model was not accurate enough to reproduce the relevant mesoscale oceanic features driving the spatial variability of the surface winds and heat fluxes. Finally, compared to in-situ and remote sensing observations, the numerical modelling weather forecast produced realistic atmospheric conditions over the sea south of the Subtropical Front. PUBLICATION ABSTRACT
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The region south of South Africa, encompassing the Agulhas Current and Retroflection, and part of the Southern Ocean, is known for its severe meteorological conditions. Because of these conditions, ...in-situ observations are rare. Consequently, remote-sensing satellite observations and high-resolution regional weather forecasts at the ocean surface are difficult to assess. However, atmospheric data collected in the southern hemisphere summer of 2008 during the International Polar Year-BONUS-GoodHope campaign were used to validate two satellite data sets: the twice daily QuikSCAT winds and the daily OAflux data set of latent and sensible heat fluxes. The surface winds and heat fluxes forecasts produced by a regional atmospheric model were also assessed along the ship track. In this study, we have shown that the two data sets exhibited a very good accordance with daily in-situ observations. During the campaign, the correlation coefficients for wind speed and direction were 0.97 and 0.91, respectively, and those for latent and sensible heat fluxes were 0.92 and 0.90, respectively. The QuikSCAT wind speed was underestimated by 1.37 m/s relative to in-situ data, south of the Subtropical Front. Large differences in heat fluxes in both OAflux and the atmospheric model were observed when crossing the Subtropical Front and a warm eddy, as well as during a storm, when gale force winds reached more than 20 m/s. The two data sets were then used to assess the regional model forecasts over a larger area south of South Africa, not limited to the ship track. Most of the model errors were located in a region north of the Subtropical Front, where the sea surface temperature used by the model was not accurate enough to reproduce the relevant mesoscale oceanic features driving the spatial variability of the surface winds and heat fluxes. Finally, compared to in-situ and remote sensing observations, the numerical modelling weather forecast produced realistic atmospheric conditions over the sea south of the Subtropical Front.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The region south of South Africa, encompassing the Agulhas Current and Retroflection, and part of the Southern Ocean, is known for its severe meteorological conditions. Because of these conditions, ...in-situ observations are rare. Consequently, remote-sensing satellite observations and high-resolution regional weather forecasts at the ocean surface are difficult to assess. However, atmospheric data collected in the southern hemisphere summer of 2008 during the International Polar Year-BONUS-GoodHope campaign were used to validate two satellite data sets: the twice daily QuikSCAT winds and the daily OAflux data set of latent and sensible heat fluxes. The surface winds and heat fluxes forecasts produced by a regional atmospheric model were also assessed along the ship track. In this study, we have shown that the two data sets exhibited a very good accordance with daily in-situ observations. During the campaign, the correlation coefficients for wind speed and direction were 0.97 and 0.91, respectively, and those for latent and sensible heat fluxes were 0.92 and 0.90, respectively. The QuikSCAT wind speed was underestimated by 1.37 m/s relative to in-situ data, south of the Subtropical Front. Large differences in heat fluxes in both OAflux and the atmospheric model were observed when crossing the Subtropical Front and a warm eddy, as well as during a storm, when gale force winds reached more than 20 m/s. The two data sets were then used to assess the regional model forecasts over a larger area south of South Africa, not limited to the ship track. Most of the model errors were located in a region north of the Subtropical Front, where the sea surface temperature used by the model was not accurate enough to reproduce the relevant mesoscale oceanic features driving the spatial variability of the surface winds and heat fluxes. Finally, compared to in-situ and remote sensing observations, the numerical modelling weather forecast produced realistic atmospheric conditions over the sea south of the Subtropical Front.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The region south of South Africa, encompassing the Agulhas Current and Retroflection, and part of the Southern Ocean, is known for its severe meteorological conditions. Because of these conditions, ...in-situ observations are rare. Consequently, remote-sensing satellite observations and high-resolution regional weather forecasts at the ocean surface are difficult to assess. However, atmospheric data collected in the southern hemisphere summer of 2008 during the International Polar Year-BONUS-GoodHope campaign were used to validate two satellite data sets: the twice daily QuikSCAT winds and the daily OAflux data set of latent and sensible heat fluxes. The surface winds and heat fluxes forecasts produced by a regional atmospheric model were also assessed along the ship track. In this study, we have shown that the two data sets exhibited a very good accordance with daily in-situ observations. During the campaign, the correlation coefficients for wind speed and direction were 0.97 and 0.91, respectively, and those for latent and sensible heat fluxes were 0.92 and 0.90, respectively. The QuikSCAT wind speed was underestimated by 1.37 m/s relative to in-situ data, south of the Subtropical Front. Large differences in heat fluxes in both OAflux and the atmospheric model were observed when crossing the Subtropical Front and a warm eddy, as well as during a storm, when gale force winds reached more than 20 m/s. The two data sets were then used to assess the regional model forecasts over a larger area south of South Africa, not limited to the ship track. Most of the model errors were located in a region north of the Subtropical Front, where the sea surface temperature used by the model was not accurate enough to reproduce the relevant mesoscale oceanic features driving the spatial variability of the surface winds and heat fluxes. Finally, compared to in-situ and remote sensing observations, the numerical modelling weather forecast produced realistic atmospheric conditions over the sea south of the Subtropical Front.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Our purpose in this paper is to assess a debate regarding retroflection as a constant contact interruption in contemporanity. We intend to approach the subject in question by taking Gestalt-therapy ...as main theoretical reference and evoking authors whom exam contemporanity, such as Guy Debord and Stuart Hall. Retroflection is understood as an interruption of the creative adjustment that obstructs contact when it comes to interaction, which means, the individual dismiss contact with others, instead of interacting he turns to himself the energy that would otherwise flow to the relation. This dynamic seems to evolve a kind of individualism present and valued in contemporanity world: self-sufficiency, self-control, permanent urge for activity and being busy, belief that others are not available and therefore: “I must solve my problems on my own, I can handle it alone”. The power of achievement and success create part of the contemporanity set, which detains the consumerism - a vehicle for spectacle - that disguise the emptiness and loneliness.
Moored current measurements carried out from 6 October 2003 to 18 February 2004 over the French Guiana continental shelf are presented. Two contrasted situations have been evidenced in which the ...currents were either weak and oscillating during the first period (from October to early December) or strong and northwestward during the rest of the survey. Further analysis of these measurements in light of Moderate Resolution Imaging Spectroradiometer satellite images have revealed that these situations are mainly due to the motion of an outer shelf mesoscale feature: the North Brazil Current (NBC) retroflection. Two other main results have also been evidenced in this survey: (1) When the NBC retroflection occurs northwestward of the French Guiana continental shelf, part of the NBC climbs over the shelf slope and propagates to the inner shelf, and (2) the “Guyana current” does not persist throughout the year at a 22 m depth and below. Finally, the location of the NBC retroflection has also a strong impact on the spread of the Amazon plume over the French Guiana continental shelf and is felt to have an influence on the nutrient supply in this region.
The inter-ocean exchange of water masses at the Agulhas Current termination comes about through the shedding of rings, and this process plays an important role in the global thermohaline circulation. ...Using several hydrographic sections collected during the ARC (Agulhas Retroflection Cruise), MARE (Mixing of Agulhas Rings Experiment) and WOCE (World Ocean Circulation Experiment), this investigation aims to establish the degree to which Red Sea Intermediate Water (RSIW) is involved in this exchange and at what level of purity. To this end a wide range of hydrographic parameters were used. Upstream from the Agulhas Current retroflection water with clear RSIW origin is shown to move downstream on both the landward and seaward sides of the Agulhas Current with the highest water sample purity or water-mass content exceeding 15%. The least mixed water was found close to the continental shelf. At the retroflection the RSIW purity shows considerable variability that ranges between 5% and 20%. This suggests that RSIW moves down the current in patches of considerably varying degrees of previous mixing. This pattern was also observed in a ring sampled during the ARC experiment. The MARE sections in turn indicate that at times RSIW may be entirely absent in the Agulhas Current. RSIW is therefore shown to travel down the current as discontinuous filaments, and this intermittency is reflected in its presence in Agulhas Rings. From the sections investigated it is therefore clear that any calculation of RSIW fluxes involved in inter-ocean exchange can only be done on the basis of event scales. RSIW not trapped in Agulhas Rings flows east with the Agulhas Return Current.
A theoretical analysis of the principal oceanic ring parameters (tangential and angular velocities, shape function, horizontal and vertical scale of the ring) is described. The theoretical model ...consists of a reduced gravity model of the lens-like vortices with solid body rotation. The application of this approach is tested by comparison with data from the North Brazil Current Rings Experiment and remote sensing data. Specifically, we used the data corresponding to the surfaceintensified North Brazil Current ring (R-3) surveyed in February–March 1999, using direct velocity and hydrographical measurements. The theoretical model was used for evaluating the geometrical structure of the surface-intensified rings that produce remarkable signals in satellite data. The principal ring parameters from the model were compared with those from satellite data (altimetry and drifter information), which were estimated by using the method of minimization of the multivariable objective functions. Although the proposed model is linear in its conception, a good agreement was observed between the model and the primary characteristics of the observed rings. The model, however, allows for improvement in its assumptions, since its application is rather limited to intense ocean rings.
The transfer of upper kilometer water from the Indian Ocean into the South Atlantic, the Agulhas leakage, is believed to be accomplished primarily through meso-scale eddy processes. There have been ...various studies investigating eddies of the “Cape Basin Cauldron” from specific data sets. The hydrographic data archive acquired during the last century within the Cape Basin region of the South Atlantic provides additional insight into the distribution and water mass properties of the Cape Basin eddies. Eddies are identified by mid-thermocline isopycnal depth anomalies relative to the long-term mean. Positive depth anomalies (the reference isopycnal is deeper than the long-term mean isopycnal depth) mark the presence of anticyclonic eddies; negative anomalies mark cyclonic eddies. Numerous eddies are identified in the whole region; the larger isopycnal displacements are attributed to the energetic eddies characteristic of the Cape Basin and indicate that there is a 2:1 anticyclone/cyclone ratio. Smaller displacements of the less energetic features are almost equally split between anticyclones and cyclones (1.4:1 ratio). Potential temperature, salinity and oxygen relationships at thermocline and intermediate levels within each eddy reveal their likely origin. The eddy core water is not solely drawn from Indian Ocean: tropical and subtropical South Atlantic water are also present. Anticyclones and cyclones carrying Agulhas Water properties are identified throughout the Cape Basin. Anticyclones with Agulhas Water characteristics show a predominant northwest dispersal, whereas the cyclones are identified mainly along the western margin of the African continent, possibly related to their origin as shear eddies at the boundary between the Agulhas axis and Africa. Cyclones and anticyclones carrying pure South Atlantic origin water are identified south of 30°S and west of the Walvis Ridge. Tropical Atlantic water at depth is found for cyclones north of the Walvis Ridge, west of 10°E and for stations deeper than 4000
m, and a few anticyclones with the same characteristics are found south of the ridge.
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