Bóias de deriva rastreadas por satélites tem se constituído em um importante componente de trabalhos de campo realizados durante diversos estudos internacionais da circulação oceânica e de programas climáticos oceânicos ocorridos nos últimos 19 anos. O experimento First GARP Global Experiment (FGGE), realizado em 1978-1979, utilizou cerca de 365 bóias de deriva nos oceanos do Hemisfério Sul. Passados 10 anos do FGGE, a tecnologia das bóias oceanográficas evoluiu significativamente, tendo sido empregada em atividades de pesquisa de menor escala. O primeiro grande programa a utilizar modernas bóias de deriva, ou derivadores como são normalmente denominados, foi o Surface Velocity Programme (SVP), do World Ocean Circulation Experiment (WOCE), ocorrido na primeira metade da década de 1990. Por outro lado, o desenvolvimento e aplicação de bóias oceanográficas, em estudos de campo no Brasil, foram iniciados em meados da década de 1980, no âmbito do Programa Antártico Brasileiro (PROANTAR). A participação brasileira em programas internacionais foi iniciada com o SVP/WOCE, tendo sua continuidade mantida no âmbito do CLIVAR, que vem a ser o sucessor do WOCE. Devido ao interesse nacional na Antártica, o Brasil é membro do International Program for Antartic Buoys (IPAB), e mais recentemente, tornou-se membro do International South Atlantic Buoy Programme (ISABP). Um novo programa nacional de bóias (PNBÓIA) foi recentemente aprovado, e a aquisição e lançamento de derivadores padrão WOCE/TOGA deverá ser iniciada em 1997. Em outro grande projeto de colaboração entre o INPE e a PETROBRÁS, serão também lançados derivadores padrão WOCE/TOGA, ainda em 1997.

Satellite tracked drifting buoys have become an important field component in several international studies of ocean circulation and related marine climate programs over the past 19 years. The First GARP Global Experiment (FGGE) took place in 1978-1979 and utilized about 365 drifting buoys in the southern hemisphere oceans. About 10 years then passed, during which time the buoy technology underwent significant improvements that were used in smaller scale research activities. The first large program to use modern drifting buoys, or drifters as they are often called, occurred during the Surface Velocity Programme (SVP) of the World Ocean Circulation Experiment (WOCE), during the early to mid 1990's. In contrast, buoy development and use in Brazilian field studies began in the mid 1980's, within the national antarctic research program (PROANTAR). Brazilian participation in international programs began with SVP/WOCE and is continuing within CLIVAR, the follow-on program to WOCE. Because of its interest in Antarctica, Brazil is also a member of the International Program for Antarctic Buoys (IPAB) and more recently of the International South Atlantic Buoy Programme (ISABP). A new national buoy program (PNBÓIA) has been approved and acquisition and deployment of WOCE/TOGA type drifters should begin in 1997. In another large project, PETROBRAS, the national oil company, will be collaborating with INPE in the launch of similar drifters, also planned for 1997.

Para obter informações sobre a variação espacial da estrutura térmica e localizar a Corrente do Brasil, ao norte e ao sul dos bancos submarinos localizados a 20º30'S realizou-se, em abril de 1982, um levantamento oceanográfico nessa região. Dados de sensoriamento remoto foram também obtidos durante os trabalhos experimentais para um delineamento sinótico da estrutura térmica de superfície. Observou-se, ao longo da maioria das secções, um "thermostad" de 23ºC na termoclina principal. Ao longo das secções com intenso sinal baroclfnico, tal como na secção ao largo de Cabo Frio, o "thermostad" atenua-se e finalmente desaparece nas proximidades da costa, de forma semelhante ao desaparecimento da água de 18ºC na parede norte da Corrente do Golfo. A estrutura da corrente e o transporte de volume, relativos à superfície isobárica de 500 dbar, foram obtidos usando-se os dados hidrográficos e também as medidas com XBX as quais foram realizadas com espaçamentos muito menores do que o das estações hidrográficas. A comparação desses resultados, para o conjunto de observações conduzidas ao largo de Cabo Frio, indica que detalhes da corrente geostrófica não são delineados quando da utilização dos dados hidrográficos; os correspondentes valores do transporte de volume diferem em aproximadamente 17% (33 e 2,8 Sv, calculados com dados hidrográficos'e de XBX respectivamente). O balanço do transporte de volume, através de todas as secções entre 19 e 22º5, indica que a Corrente do Brasil flui através da passagem entre os bancos localizados mais próximos da costa. O transporte de volume resultante (2,9 Sv) é muito próximo do valor obtido através da secção ao largo de Cabo Frio, onde supõe-se que a extensão transversal da Corrente do Brasil foi delimitada pelo conjunto de observações.

In April 1982, an oceanographie investigation was conducted off the Brazilian coast in order to obtain the spatial characteristics of the thermal structure and to locate the Brazil Current flow both north and south of the seamount chain at 20º30'S. Dining the survey, remote sensing satellite data were also obtained on several occasions to assist in the delineation of the surface thermal structure. A 23ºC thermostad was observed along most sections. Along sections with stronger baroclinic signatures, such as the one in Cabo Frio, the thermostad seems to be pinched off somewhat similar to the pinching off the 18ºC water in the Gulf Stream North wall. The current structure and volume transports, relative to the 500 dbar isobaric surface, were calculated using both hydrographie station data and the closely spaced XBT measurements. A comparison of these results, for the data observed along the section of Cabo Frio, indicates that some details of the geostrophic currents are lost when the hydrographie data are used; the corresponding volume transports agree within 17% (33 Sv using hydrographie data against 2.8 Sv using XBT data). A volume transport budget, obtained through the transport computation along all sections between 19º and 22ºS, indicates that the Brazil Current appears to flow through the passage between the most inshore banks and not to the east. The net volume transport (2.9 Sv) is in close agreement with the Cabo Frio section volume transport, where the total flow of the Brazil Current was supposedly bracketed by the station sampling.

The objective of this work is to study the possibility of estimating the heat flux balance at the sea surface from GOSSTCOMP (Global Ocean Sea Surface Temperature Computation) developed by NOAA/NESS, USA, and sea surface current data based from ships drift information obtained from Pilot Charts, published by the Diretoria de Hidrografia e Navegação (DHN, Brazilian Navy). The annual mean value of the heat flux balance at the sea surface off southeast Brazil for 1977, is estimated from data on the balance between the heat transported by the currents and that transported by eddy diffusion for each volume defined as 2º x 2º (Lat. x Long.) square with a constant depth equivalent to an oceanic mixed layer, 100 m thick. Results show several oceanic areas where there are net flows of heat from atmosphere towards the sea surface. In front of Rio de Janeiro the heat flow was downward and up to 70 ly day-1 and is probably related to the upwellirug phenomenon normally occurring in that area. Another coastal area between Lat. 25ºS to 28ºS indicated an downward flow up to 50 ly day-1; and for an area south of Lat. 27ºS, Long. 040ºW - 048ºW an downward flow up to 200 ly day-1, where the transfer was probably due to the cold water of a nortward flux from the Falkland (Malvinas) Current. Results also show several oceanic areas where net flows of heat (of about -100 ly day-1) were toward the atmosphere. In the oceanic areas Lat. 19ºS - 23ºS and Lat. 24ºS - 30ºS, the flows were probably due to the warm water of a southward flux of the Brazil Current. The resulting fluxes from the warm waters of the Brazil Current when compared with those from warm waters of the Gulf Stream and Kuroshio, indicate that the Gulf Stream carries about 3.3 times and the Kuroshio 1.7 times more heat than the Brazil Current. These values agree with those of data available on the heat fluxes of the above mentioned Currents calculated by different methods (Budyko, 1974).

Seasonal differences in sigma-t (1.8)3 temperature (4.0ºC) and salinity (0.9‰) were observed during February/June 1976 in the vicinity of Ilha Grande off the coast of Brazil Estimates of static and dynamic stability were made through the calculation of Brunt-Vaisala frequencies and Richardson numbers, respectively. Both static and dynamic stability values were larger in February than in June for the same location and suggest a greater column stability in February than in June. Stations located in the northern and western channels of Ilha Grande, however, contained greater density reversals than to the east of the Island. Small scale dispersion studies were made using Rhomamine B dye to determine horizontal diffusion coefficients (K) east of the Island and in an embayment of the Island. The estimate for K was 9X10³ cm² s-1 east of the Island, about 2.6 times greater than the value estimated for the protected embayment.

A mesosoale study was made of the Ilha Grande area. The local circulation described through -progressive vector diagrams showed a clochwise bottom circulation determined in June 1976, while in the upper 10 m the direction of the flow entering the Ilha Grande Bay was towards the center in the west and towards the Marambaia sandbank in the east side of the Bay. Short periods and amplitude fluctuations were evaluted using power spectral analysis, Fourier and Maximum Entropy Method, which showed that in the upper 10 m predominant periods decrease from 1.1h (A = 6.3cm sec-1) (position = 3C) to 1.0h (A = 7.4 cm sec-1) (position = 2D) and increase to 5.8h (A = 6.8 cm., sec-1) (position = ID), while at the bottom layer the predominant period increases from 0.4 h (A = 5.0 cm sec-1) (position = 3G) to 6.4h (A = 7.0 cm sec-1) (position = 2G) and to 4.4h (A = 7.9 cm sec-1) (position = 1G) . From the original data it has been possible to determine an "intense pulsation" between 30-70 cm sec-1 in the upper 10 m with about 1.0h period and 10-20 min duration in all the stations.