Luiz Paulo de Freitas Assad

A 4D-variational ocean data assimilation application for Santos Basin, Brazil

Aiming to achieve systematic ocean forecasting for the southeastern Brazilian coast, an incremental 4D-Var data assimilation system is applied to a regional ocean model focused mainly in the Santos Basin region. This implementation is performed within the scope of The Santos Basin Ocean Observing System (or Project Azul), a pilot project designed to collect oceanographic data with enough frequency and spatial coverage so to improve regional forecasts through data assimilation. The ocean modeling and data assimilation system of Project Azul is performed with the Regional Ocean Modeling System (ROMS). The observations used in the assimilation cycles include the following: 1-day gridded, 0.1° resolution SST from POES AVHRR; 1-day gridded, 0.3° composite of the MDT SSH from AVISO; and surface and subsurface hydrographic measurements of temperature and salinity collected with gliders and ARGO floats from Project Azul and from UK Met-Office EN3 project dataset. The assimilative model results are compared to forward model results and independent observations, both from remote sensing and in situ sources. The results clearly show that 4D-Var data assimilation leads to an improvement in the skill of ocean hindcast in the studied region.

Estudo da influência das anomalias da TSM do Atlântico Sul extratropical na região da Confluência Brasil-Malvinas no regime hidrometeorológico de verão do Sul e Sudeste do Brasil

This study analyses the influence of the extratropical South Atlantic sea surface temperature (SST) anomalies in the Southern and Southeastern Brazilian hydrometeorological pattern. The Brazil-Malvinas Confluence (BMC) is one of the most important South Atlantic Ocean features. This region is characterized by a strong thermal front formed by the confluence between the warm waters transported by the Brazil Current (BC) and the cold waters carried by the Malvinas Current (MC). The knowledgement of its dynamics could represent an important advance to understand its connection with locally and remotely generated ocean and atmospheric processes. This investigation is made with computational modeling using a Community Atmosphere Model (CAM 2.01). The spatial and time SST anomalies were numerically generated inside the model code in such a way to reproduce the summer 2005 event. Significant changes were observed in this experiment in the vertical atmospheric circulation pattern. The precipitation over South Brazil region decreased and more favorable conditions to the South Atlantic Convergence Zone (SACZ) formation appeared over the northern part of the Southeastern Brazil region. These model generated patterns were similar to those observed during the summer 2005, especially the precipitation anomalies results.

Volume and heat transports in the world oceans from an ocean general circulation model

Monitoring the volume and heat transports around the world oceans is of fundamental importance in the study of the climate system, its variability, and possible changes. The application of an Oceanic General Circulation Model for climatic studies needs that its dynamic and thermodynamic fields are in equilibrium. The time spent by the model to reach this equilibrium is called spin-up time. This work presents some results obtained from the application of the Modular Ocean Model version 4.0 initialized with temperature, salinity, velocity and sea surface height data already in equilibrium from an ocean data assimilation experiment conducted by Geophysical Fluid Dynamics Laboratory (GFDL). The use of this dataset as initial condition aimed to diminish the spin-up time of the oceanic model. The model was integrated for seven years. Volume and heat transports in different sections around the world oceans showed to be in good agreement with the literature. The results showed a well defined seasonal cycle starting at the second integration year, also some important dynamic and thermodynamic aspects of the Global Ocean Circulation, as the great conveyor belt, are well reproduced. The obtained results could constitute an important data source to be used as initial and boundary conditions in regional ocean model experiments as well as for long integration runs in order to study oceanic climate variability.

Projeto Azul: Operational Oceanography in an Active Oil and Gas Area Southeastern Brazil

This chapter describes the ocean observation and data assimilation modules of Projeto Azul, a three-year operational oceanography pilot program for Santos Basin (southeastern Brazil from 23oS to 28oS) started in 2013. Systematic data collection in the Brazil Current meander and Cabo Frio eddy was performed by satellite-tracked surface drifters (surface currents, temperature, and atmospheric pressure), floats (vertical profiles of temperature and salinity), and gliders (vertical profiles of temperature, salinity, dissolved oxygen, turbidity, chlorophyll, and dissolved organic matter) creating an unforeseen data density in the region. The first tests of a 4D-VAR data assimilation scheme on a ROMS regional grid suggest an improvement of the ocean modeling short-range forecasts for the Santos Basin.

Three-dimensional oil dispersion model in the Campos Basin, Brazil

ABSTRACT This paper presents the physical and mathematical formulation of a three-dimensional oil dispersion model that calculates the trajectory from the seafloor to the sea surface, its assumptions and constraints. It was developed by researchers who are familiar with oil spill dispersion and mathematical analysis. Oil dispersion is calculated through two computational routines. The first calculates the vertical dispersion along the water column and resamples the droplets when the oil reaches the surface. The second calculates the surface displacement of the spill. This model is based on the Eulerian approach, and it uses numerical solution schemes in time and in space to solve the equation for advective–diffusive transport. A case study based on an actual accident that happened in the Campos Basin, in Rio de Janeiro state, considering the instant spill of 1000 m3 was used to evaluate the proposed model. After calculating the vertical transport, it was estimated that the area covered by the oil spill on the surface was about 35,685 m². After calculating the dispersion at the surface, the plume area was estimated as 20% of the initial area, resulting in a final area of 28,548 m².

Downscaling of the global HadGEM2-ES results to model the future and present-day ocean conditions of the southeastern Brazilian continental shelf

Changes in the regional hydrodynamics of the region of the South Atlantic near the east coast of Brazil were evaluated from the beginning to the end of the century. The analysis was based on the anomalies from two downscaling experiments using the HadGEM2-ES outputs for the historical and RCP4.5 runs from the Coupled Model Inter-comparison Project phase 5. The anomalies between the experiments were collected in a system of two nested grids, with

The Ocean Observing System for Santos Basin: Project Blue

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VOLUME AND HEAT TRANSPORTS ANALYSIS IN THE SOUTH ATLANTIC BASIN RELATED TO CLIMATE CHANGE SCENARIOS

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