A maré terrestre: aspectos teóricos e práticos
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Data
2020-03-04
Autores
Arana, Daniel [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Existem dados de estações de maré terrestre em todo território nacional que estiveram em operação nos últimos anos. Contudo cada região de coleta apresenta um ou mais efeitos geofísicos predominantes, causando uma heterogeneidade dos dados e abrindo a possibilidade para diversos estudos. A minimização de efeitos geofísicos em observações gravimétricas é um grande desafio na geração de modelos de maré terrestre. Desta forma, esta pesquisa tem como objetivo estudar as metodologias para correções das cargas atmosférica e oceânica nos diferentes cenários. A hipótese adotada nesta pesquisa é que a consideração do parâmetro temporal junto à análise espectral possibilita isolar a maré terrestre e as sobrecargas. A metodologia neste trabalho envolve três etapas: (1) o pré-processamento, (2) o processamento das observações gravimétricas e (3) a aplicação dos modelos de marés. As estações base do estudo são PPTE e NEIA, localizadas respectivamente nos municípios de Presidente Prudente - SP e Cananeia - SP, escolhidas em razão do comportamento distinto das cargas oceânicas nas duas regiões. A pesquisa fundamenta-se na decomposição por harmônicos esféricos e pelo uso de ondaletas na série temporal gravimétrica das duas estações. O pré-processamento dos dados foi minuciosamente realizado, destaca-se a detecção de um deslocamento temporal em parte dos dados gravimétricos de PPTE, que foram corrigidos com sucesso. Na etapa do processamento foram analisados os impactos das correções atmosféricas e oceânicas. Para a manutenção do sentido físico das constituintes de maré na correção da carga atmosférica é recomendada a utilização de um fator de admissibilidade teórico associado a modelos meteorológicos globais. Os modelos de sobrecarga oceânica mostraram dificuldade na total minimização do efeito, principalmente na região costeira. Nestes cenários é vantajoso a utilização de modelos empíricos de marés que englobados em cada constituinte a maré sólida e efeitos de sobrecarga. Em relação à análise espectro-temporal, a modificação da frequência fundamental da ondaleta mãe é essencial para a separação das constituintes de maré. Para a extensão da série temporal dos dados gravimétricos em ~ 10 meses, interpolados para 1 h, a utilização da frequência fundamental em 400 Hz permitiu a separação de 13 constituintes. Na obtenção dos fatores gravimétricos e fases, os experimentos mostraram compatibilidade entre os resultados obtidos com o ETERNA e com a Transformada em Ondaletas. Os resultados obtidos na análise espectro temporal mostraram que é possível obter as sobrecargas extraídas dos dados gravimétricos por meio da consideração de um modelo elástico teórico.
There are Earth tide data from stations across the country that have been in operation in recent years. However, each collection region has one or more predominant geophysical effects, causing a heterogeneity of data and opening the possibility for several studies. The minimization of geophysical effects in gravimetric observations is a major challenge in the generation of terrestrial tide models. Thus, this research aims to study the methodologies for correcting atmospheric and ocean loading in different scenarios. The hypothesis adopted in this research is that the consideration of the temporal parameter together with the spectral analysis makes it possible to isolate the terrestrial tide and the overloads. The methodology in this work involves three stages: (1) the pre-processing, (2) the processing of the gravimetric observations and (3) the application of the tidal models. The study stations are PPTE and NEIA, located respectively in the cities of Presidente Prudente - SP and Cananeia - SP, chosen due to the different behavior of ocean loading in the two regions. The research is based on the decomposition by spherical harmonics and the use of wavelets in the gravimetric time series of the two stations. The pre-processing of the data was meticulously carried out, highlighting the detection of a temporal displacement in part of the PPTE gravimetric data, which were successfully corrected. In the processing stage, the impacts of atmospheric and oceanic corrections were analyzed. To maintain the physical meaning of tidal constituents, for the atmospheric loading correction it is recommended to use a theoretical admissibility factor associated with global meteorological models. Ocean tide loading models showed difficulty in minimizing the effect, especially in the coastal region. In these scenarios, it is advantageous to use empirical tidal models that include in each constituent the solid tide and overload effects. Regarding the spectral-temporal analysis, the modification of the fundamental frequency of the mother wave is essential for the separation of the tidal constituents. For the time series extension of gravimetric data in ~ 10 months, interpolated for 1 h, the use of the fundamental frequency in 400 Hz allowed the separation of 13 constituents. In obtaining the gravimetric factors and phases, the experiments showed compatibility between the results obtained with ETERNA and with the Waveform Transform. The results obtained in the temporal spectrum analysis showed that it is possible to obtain the overloads extracted from the gravity data by considering a theoretical elastic model.
There are Earth tide data from stations across the country that have been in operation in recent years. However, each collection region has one or more predominant geophysical effects, causing a heterogeneity of data and opening the possibility for several studies. The minimization of geophysical effects in gravimetric observations is a major challenge in the generation of terrestrial tide models. Thus, this research aims to study the methodologies for correcting atmospheric and ocean loading in different scenarios. The hypothesis adopted in this research is that the consideration of the temporal parameter together with the spectral analysis makes it possible to isolate the terrestrial tide and the overloads. The methodology in this work involves three stages: (1) the pre-processing, (2) the processing of the gravimetric observations and (3) the application of the tidal models. The study stations are PPTE and NEIA, located respectively in the cities of Presidente Prudente - SP and Cananeia - SP, chosen due to the different behavior of ocean loading in the two regions. The research is based on the decomposition by spherical harmonics and the use of wavelets in the gravimetric time series of the two stations. The pre-processing of the data was meticulously carried out, highlighting the detection of a temporal displacement in part of the PPTE gravimetric data, which were successfully corrected. In the processing stage, the impacts of atmospheric and oceanic corrections were analyzed. To maintain the physical meaning of tidal constituents, for the atmospheric loading correction it is recommended to use a theoretical admissibility factor associated with global meteorological models. Ocean tide loading models showed difficulty in minimizing the effect, especially in the coastal region. In these scenarios, it is advantageous to use empirical tidal models that include in each constituent the solid tide and overload effects. Regarding the spectral-temporal analysis, the modification of the fundamental frequency of the mother wave is essential for the separation of the tidal constituents. For the time series extension of gravimetric data in ~ 10 months, interpolated for 1 h, the use of the fundamental frequency in 400 Hz allowed the separation of 13 constituents. In obtaining the gravimetric factors and phases, the experiments showed compatibility between the results obtained with ETERNA and with the Waveform Transform. The results obtained in the temporal spectrum analysis showed that it is possible to obtain the overloads extracted from the gravity data by considering a theoretical elastic model.
Descrição
Palavras-chave
Transformada em Ondaletas, Sobrecarga oceânica, Sobrecarga atmosférica, Gravimetria, Maré terrestre, gPhone, Wavelets transform, Ocean load, Atmospheric load, Body tide