ASSIMILATION OF SEA SURFACE HEIGHT ANOMALIES INTO HYCOM WITH AN OPTIMAL INTERPOLATION SCHEME OVER THE ATLANTIC OCEAN METAREA V

2014 ◽  
Vol 31 (2) ◽  
Author(s):  
Clemente Augusto Souza Tanajura ◽  
Filipe Bitencourt Costa ◽  
Renato Ramos da Silva ◽  
Giovanni Abdelnur Ruggiero ◽  
Victor Bastos Daher
Keyword(s):  
Interpolation Method ◽  
Maximum Error ◽  
Sea Surface Height ◽  
Volume Transport ◽  
Ocean Model ◽  
Sea Surface ◽  
Height Anomaly ◽  
Optimal Interpolation ◽  
Sea Surface Height Anomaly ◽  
The Impact

Along-track sea surface height anomaly (SSHA) data from the Jason-1 and Jason-2 satellites were assimilated into the ocean model HYCOM from July 1, 2009 until December 31, 2009. A new and simple approach to overcome the bias between the model and observed SSHA was proposed. It focuses on the meso-scale differences between the data and the model along each satellite track. An optimal interpolation method and the Cooper and Haines (1996) scheme (C&H) were employed to produce a SSHA analysis field and to adjust model layer thicknesses over the Atlantic METAREA V. The corrected model state was used as initial condition for the next assimilation cycle. SSHA data with a 7-day window were assimilated in 3-day intervals centered in the SSHA data window and the C&H scheme was applied taking the SSHA analysis. A control run without assimilation was also performed. The results showed that the model SSHA was completely reorganized by the end of the experiment. The modifications of SSHA were compared to the American Navy HYCOM+NCODA system and AVISO data. Maximum error was reduced from 0.7 m to 0.2 m by assimilation. Comparisons were also made with the Argo temperature and salinity vertical profiles. Improvements in the currents and volume transport were also produced by assimilation. The impact in temperature was in general positive, but there was no substantial modification in salinity.

scholarly journals ASSIMILATION OF SEA SURFACE HEIGHT ANOMALIES INTO HYCOM WITH AN OPTIMAL INTERPOLATION SCHEME OVER THE ATLANTIC OCEAN METAREA V

2013 ◽  
Vol 31 (2) ◽  
pp. 257 ◽  
Author(s):  
Clemente Augusto Souza Tanajura ◽  
Filipe Bitencourt Costa ◽  
Renato Ramos da Silva ◽  
Giovanni Abdelnur Ruggiero ◽  
Victor Bastos Daher
Keyword(s):  
Interpolation Method ◽  
Maximum Error ◽  
Sea Surface Height ◽  
Volume Transport ◽  
Ocean Model ◽  
Sea Surface ◽  
Height Anomaly ◽  
Optimal Interpolation ◽  
Ocean Data Assimilation ◽  
The Impact

ABSTRACT. Along-track sea surface height anomaly (SSHA) data from the Jason-1 and Jason-2 satellites were assimilated into the ocean model HYCOM from July 1, 2009 until December 31, 2009. A new and simple approach to overcome the bias between the model and observed SSHA was proposed. It focuses on the meso-scale differences between the data and the model along each satellite track. An optimal interpolation method and the Cooper & Haines (1996) scheme (C&H) were employed to produce a SSHA analysis field and to adjust model layer thicknesses over the Atlantic METAREA V. The corrected model state was used as initial condition for the next assimilation cycle. SSHA data with a 7-day window were assimilated in 3-day intervals centered in the SSHA data window and the C&H scheme was applied taking the SSHA analysis. A control run without assimilation was also performed. The results showed that the model SSHA was completely reorganized by the end of the experiment. The modifications of SSHA were compared to the American Navy HYCOM+NCODA system and AVISO data. Maximum error was reduced from 0.7 m to 0.2 m by assimilation. Comparisons were also made with the Argo temperature and salinity vertical profiles. Improvements in the currents and volume transport were also produced by assimilation. The impact in temperature was in general positive, but there was no substantial modification in salinity.   Keywords: ocean data assimilation, Jason-1 and Jason-2 satellites, Argo. RESUMO. Dados de anomalia da altura da superfície do mar (AASM) dos satellites Jason-1 e Jason-2 foram assimilados no modelo oceânico HYCOM de 1 de julho de 2009 a 31 de dezembro de 2009. Um nova e simples abordagem foi proposta para superar o viés entre os dados observados de AASM e o campo do modelo. Ela enfoca as diferenças entre o modelo e as observações na mesoescala ao longo de cada trilha dos satélites. Um método de interpolação estatística e o esquema de Cooper & Haines (1996) (C&H) foram empregados para produzir um campo de análise de AASM e ajustes nas espessuras das camadas do modelo sobre a METAREA V do Atlântico. O estado corrigido do modelo foi usado como condição inicial para o próximo ciclo de assimilação. Dados de AASM em uma janela de 7 dias foram assimilados a cada 3 dias em data centrada na janela de dados e o método de C&H foi aplicado com a análise de AASM. Os resultados mostraram que a AASM do modelo foi completamente reorganizada no final do experimento. As modificações de AASM foram comparadas com análises globais do sistema Americano HYCOM+NCODA e com dados do AVISO. Erros máximos foram reduzidos de 0,7 m para 0,2 m com a assimilação. Comparações foram também feitas com perfis verticais de temperatura e salinidade do Argo. Melhorias nas correntes e no transporte de volume foram produzidas em relação à rodada de controle. O impacto na temperatura foi em geral positivo, mas não houve modificação substancial na salinidade.   Palavras-chave: assimilação de dados oceanográficos, satélites Jason-1 e Jason-2, Argo.

scholarly journals A STUDY OF THE IMPACT OF ALTIMETRY DATA ASSIMILATION ON SHORT-TERM PREDICTABILITY OF THE HYCOM OCEAN MODEL IN REGIONS OF THE TROPICAL AND SOUTH ATLANTIC OCEAN

2013 ◽  
Vol 31 (2) ◽  
pp. 271 ◽  
Author(s):  
Leonardo Nascimento Lima ◽  
Clemente Augusto Souza Tanajura
Keyword(s):  
Data Assimilation ◽  
Sea Surface Height ◽  
Ocean Model ◽  
South Atlantic ◽  
Sea Surface ◽  
Optimal Interpolation ◽  
Altimetry Data ◽  
Hybrid Coordinate Ocean Model ◽  
Along Track ◽  
The Impact

ABSTRACT. In this study, assimilation of Jason-1 and Jason-2 along-track sea level anomaly (SLA) data was conducted in a region of the tropical and South Atlantic (7◦N-36◦S, 20◦W up to the Brazilian coast) using an optimal interpolation method and the HYCOM (Hybrid Coordinate Ocean Model). Four 24 h-forecast experiments were performed daily from January 1 until March 31, 2011 considering different SLA assimilation data windows (1 day and 2 days) and different coefficients in the parameterization of the SLA covariance matrix model. The model horizontal resolution was 1/12◦ and the number of vertical layers was 21. The SLA analyses added to the mean sea surface height were projected to the subsurface with the Cooper & Haines (1996) scheme. The results showed that the experiment with 2-day window of along-track data and with specific parameterizations of the model SLA covariance error for sub-regions of the METAREA V was the most accurate. It completely reconstructed the model sea surface height and important improvements in the circulation were produced. For instance, there was a substantial improvement in the representation of the Brazil Current and North Brazil Undercurrent. However, since no assimilation of vertical profiles of temperature and salinity and of sea surface temperature was performed, the methodology employed here should be considered only as a step towards a high quality analysis for operational forecasting systems.   Keywords: data assimilation, optimal interpolation, Cooper & Haines scheme, altimetry data.   RESUMO. Neste estudo, a assimilação de dados de anomalia da altura da superfície do mar (AASM) ao longo da trilha dos satélites Jason-1 e Jason-2 foi conduzida em uma região do Atlântico tropical e Sul (7◦N-36◦S, 20◦W até a costa do Brasil) com o método de interpolação ótima e o modelo oceânico HYCOM (Hybrid Coordinate Ocean Model). Foram realizados quatro experimentos de previsão de 24 h entre 1 de janeiro e 31 de março de 2011, considerando diferentes janelas de assimilação de AASM (1 dia e 2 dias) e diferentes coeficientes na parametrização da matriz de covariância dos erros de AASM do modelo. A resolução horizontal empregada no HYCOM foi 1/12◦ para 21 camadas verticais. As correções de altura da superfície do mar devido à assimilação de AASM foram projetadas abaixo da camada de mistura através da técnica de Cooper & Haines (1996). Os resultados mostraram que o experimento com assimilação de dados ao longo da trilha dos satélites com a janela de 2 dias e com parametrizações da matriz de covariância específicas para sub-regiões da METAREA V foi o mais acurado. Ele reconstruiu completamente a altura da superfície do mar e também proporcionou melhorias na circulação oceânica reproduzida pelo modelo. Por exemplo, houve substancial melhoria da representação nos campos da Corrente do Brasil e Subcorrente Norte do Brasil. Entretanto, tendo em vista que não foi realizada a assimilação de perfis verticais de temperatura e de salinidade e da temperatura da superfície do mar, a metodologia apresentada deve ser considerada apenas como um passo na conquista de uma análise oceânica e de um sistema previsor de qualidade para fins operacionais.   Palavras-chave: assimilação de dados, interpolação ótima, técnica de Cooper & Haines, dados de altimetria.

An application of a data assimilation method based on the diffusion stochastic process theory using altimetry data in Atlantic

2016 ◽  
Vol 31 (3) ◽  
Author(s):  
Konstantin P. Belyaev ◽  
Andrey A. Kuleshov ◽  
Clemente A. S. Tanajura
Keyword(s):  
Stochastic Process ◽  
Data Assimilation ◽  
Interpolation Method ◽  
Planck Equation ◽  
Ocean Model ◽  
Sea Surface ◽  
Process Theory ◽  
Optimal Interpolation ◽  
Computationally Efficient ◽  
The Impact

AbstractA data assimilation (DA) method based on the application of the diffusion stochastic process theory, particularly, of the Fokker-Planck equation, is considered. The method was introduced in the previous works; however, it is substantially modified and extended to the multivariate case in the current study. For the first time, the method is here applied to the assimilation of sea surface height anomalies (SSHA) into the Hybrid Coordinate Ocean Model (HYCOM) over the Atlantic Ocean. The impact of assimilation of SSHA is investigated and compared with the assimilation by an Ensemble Optimal Interpolation method (EnOI). The time series of the analyses produced by both assimilation methods are evaluated against the results from a free model run without assimilation. This study shows that the proposed assimilation technique has some advantages in comparison with EnOI analysis. Particularly, it is shown that it provides slightly smaller error and is computationally efficient. The method may be applied to assimilate other data such as observed sea surface temperature and vertical profiles of temperature and salinity.

Sea surface height anomaly and upper ocean temperature over the Indian Ocean during contrasting monsoons

2016 ◽  
Vol 75 ◽  
pp. 1-21 ◽  
Author(s):  
Anitha Gera ◽  
A.K. Mitra ◽  
D.K. Mahapatra ◽  
I.M. Momin ◽  
E.N. Rajagopal ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Sea Surface Height ◽  
Sea Surface ◽  
Height Anomaly ◽  
Upper Ocean ◽  
Ocean Temperature ◽  
The Indian Ocean ◽  
Sea Surface Height Anomaly

scholarly journals Sea surface height anomaly and geostrophic velocity from altimetry measurements over the Arctic Ocean (2011–2018)

2021 ◽  
Author(s):  
Francesca Doglioni ◽  
Robert Ricker ◽  
Benjamin Rabe ◽  
Torsten Kanzow
Keyword(s):  
Large Scale ◽  
Sea Surface Height ◽  
Sea Surface ◽  
The Arctic ◽  
Height Anomaly ◽  
Near Surface ◽  
Geostrophic Velocity ◽  
Surface Ocean ◽  
Surface Circulation ◽  
Sea Surface Height Anomaly

Abstract. In recent decades the decline of the Arctic sea ice has modified vertical momentum fluxes from the atmosphere to the ice and the ocean, thereby affecting the surface circulation. In the past ten years satellite altimetry has contributed to understand these changes. However, data from ice-covered regions require dedicated processing, originating inconsistency between ice-covered and open ocean regions in terms of biases, corrections and data coverage. Thus, efforts to generate consistent Arctic-wide datasets are still required to enable the study of the Arctic Ocean surface circulation at basin-wide scales. Here we provide and assess a monthly gridded dataset of sea surface height anomaly and geostrophic velocity. This dataset is based on Cryosat-2 observations over ice-covered and open ocean areas of the Arctic up to 88° N for the period 2011 to 2018, interpolated using the Data-Interpolating Variational Analysis (DIVA) method. Geostrophic velocity was not available north of 82° N before this study. To examine the robustness of our results, we compare the generated fields to one independent altimetry dataset and independent data of ocean bottom pressure, steric height and near-surface ocean velocity from moorings. Results from the comparison to near-surface ocean velocity show that our geostrophic velocity fields can resolve seasonal to interannual variability of boundary currents wider than about 50 km. We further discuss the seasonal cycle of sea surface height and geostrophic velocity in the context of previous literature. Large scale features emerge, i.e. Arctic-wide maximum sea surface height between October and January, with the highest amplitude over the shelves, and basin wide seasonal acceleration of Arctic slope currents in winter. We suggest that this dataset can be used to study not only the large scale sea surface height and circulation but also the regionally confined boundary currents. The dataset is available in netCDF format from PANGAEA at [data currently under review].

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