Carlos Eduardo Parente Ribeiro

Reconstituição do clima de ondas no sul-sudeste brasileiro entre 1997 e 2005

A criterious hindcasting study of the South Atlantic Ocean wave field was made using the model WAVEWATCH III including tests to evaluate which numerical grid would provide the best configuration for the wind and other atmospherics forcing regarding the calibration of the respective fields. It was observed that the wind forcing values were slightly underestimated for speeds below 7.5 m/s and overestimated for speeds above this value for specific sites at Campos and Santos Basins (Brazil). Thus, it was proposed a small correction to compensate any trends in the wind forcing values for the region. The evaluation of resultant wave fields was made using extreme measured sea states at PETROBRAS platform P-25, northern Campos Basin. The comparison of measured and modeled values shows that the adjusted atmospherics forcing provided good results for both significant wave heights (Hs) as well as spectral peak periods (Tp). Although, it was observed that the modeled sea states tend to slightly underestimate the local sea component at the initial storm buildup when a second spectral peak is present. It was also observed that the used numerical grid tends not to capture very compact atmospheric systems due to poor resolution of such small scale features. On a general view, the results reproduce the wave field characteristics of the western South Atlantic Ocean.

Improvement of directional wave information and quality control before real-time telemetry of heave-pitch-roll metocean buoys

The transmission of metocean data collected in real-time is essential for marine operations. Due to the high cost associated with satellite communication, the complete characterization of sea state is impaired. The moderns single boards computers, enables the development of dedicated modules for processing and quality control of the collected series, allowing to perform more complex tasks and transmitting additional information relevant to the characterization of sea states. The main goals of this work is to increase the reliability of real-time data, transmitted by heave-pitch-roll buoys and verify the efficiency of a single board computer to execute the traditional wave processing by Longuet-Higgins and DAAT, including automatic quality control. This new wave data processing system allows a deeper evaluation of the information that can characterize a sea state of a time series that was stored inside the buoy and was not transmitted in real-time.

ADCP's Gravity waves data processing with wavelet Matched Phase Method

This work uses data from Acoustic Doppler Current Profiler (ADCP), which form a spatial arrangement (array) of 12 sensors placed near the sea surface, to determine the directional wave spectrum by a new schema for data processing, named Matched Phase Method - MPM, that also utilizes the wavelet Data Analysis with Adaptive Technique (DAAT). The method is inverse and determines the direction of the ocean wave field, in frequency bands, based on the match between the phase observed in the cross-spectrum of different combinations of sensors of the ADCP and the theoretical phase response of each pair of sensors subjected to gravity waves of unit amplitude from different directions (transfer function). The method provides the spreading function directly, without using fitting models. The wavelet approach grants high temporal resolution for selected frequency bins representative of the ocean wave field. The MPM results were consistently robust, showing stability between results from subsequent independent records.

USE OF RAY TRACING MODELING IN SHALLOW WATER ACOUSTIC SOURCE LOCALIZATION COMBINED WITH MATCHED-FIELD PROCESSING TECHNIQUES

ABSTRACT. Underwater source localization based on acoustic modeling has been a subject of intensive research since a long time. In the case of shallow water scenarios (which are characterized by multilayered bottoms) normal-mode based acoustic propagation models are often combined with Matched-Field Processing techniques in order to provide accurate estimates of both source range and depth. This work discusses the use of a ray tracing model for source localization. Accurate predictions of the acoustic field are obtained by replacing the multilayered bottom with an equivalent (single-layer) bottom, to be used by the ray model, where the properties of the equivalent bottom are obtained through parameter optimization based on the comparison between rays (single-layer) andmodes (multilayer) predictions. The accuracy of this approach is tested using data from an experiment performed by the former Undersea Research Centre of the Supreme Allied Commander Atlantic (SACLANT) in the north of the Elba Island, near the Italian coast. The results indicate that the proposed approach allows a ray model to locate an stationary source with the same accuracy as the one achieved with a normal mode model. Keywords: underwater acoustic modeling, ray-based models, normal mode models. RESUMO. A localizacao de fontes submarinas por meio de modelos de propagacao acustica e um antigo problema de grande interesse cientifico. Em cenarios de aguas rasas, que se caracterizam normalmente por fundos com complexos sistemas multicamadas, os modelos de propagacao baseados na teoria de modos normais sao geralmente combinados com tecnicas de Processamento por Campo Casado para produzirem estimativas acuradas da distância e profundidade de uma fonte acustica. O trabalho aqui apresentado propoe a utilizacao de um modelo de tracado de raios no problema da localizacao. De maneira a produzir estimativas acuradas do campo acustico, o modelo de raios recorre a um modelo equivalente do fundo, baseado numa escolha otima de parâmetros, os quais sao obtidos por meio da comparacao entre as previsoes geradas por um modelo de raios (que considera um ambiente de camada unica) e as geradas por um modelo de modos (que considera um ambiente original multicamadas). A acuracia da metodologia e verificada por meio de dados adquiridos ao norte da Ilha de Elba (nas proximidades da costa italiana), oriundos de um experimento realizado pelo entao Undersea Research Centre of the Supreme Allied Commander Atlantic (SACLANT). Os resultados alcancados indicam que a metodogia aqui proposta demonstra ser possivel um modelo de raios para localizar uma fonte estatica com acuracia comparavel aquela tradicionalmente obtida por um modelo de modos normais. Palavras-chave: modelagem acustica submarina, modelos de raios, modelos de modos normais.