First approach to the application of operational 4DVAR data assimilation to the regional ocean model system

<p>Regional Ocean Model System (ROMS) has been simulated for the Sunda Strait, the Java Sea, and the Indian Ocean. The simulation was undertaken for thirteen months of data period (August 2013 &#8211; August 2014). However, we only used four months period for validation, namely September &#8211; December 2013. The input data involved the HYbrid Coordinate Ocean Model (HYCOM) ocean model output by considering atmospheric forcing from the European Centre for Medium-Range Weather Forecasts (ECMWF), without and with tides forcing from TPXO and rivers. The output included vertical profile temperature and salinity, sea surface temperature (SST), seas surface height (SSH), zonal (u), and meridional (v) velocity. We compared the model SST to satellite SST in time series, SSH to tides gauges data in time series, the model u and v component velocity to High Frequency (HF) radial velocity. The vertical profile temperature and salinity were compared to Argo float data and XBT. Besides, we validated the amplitude and phase of the ROMS seas surface height to amplitude and phase of the tides-gauges, including four constituents (M2, S2, K1, O1).</p>

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Assimilation of Middepth Velocities from Argo Floats in the Western South China Sea

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-d-18-0233.1 ◽

2020 ◽

Vol 37 (1) ◽

pp. 141-157

Author(s):

Pinqiang Wang ◽

Weimin Zhang ◽

Huizan Wang ◽

Haijin Dai ◽

Xiaohui Wang

Keyword(s):

Data Assimilation ◽

South China Sea ◽

South China ◽

Ocean Model ◽

Trajectory Data ◽

Argo Float ◽

Argo Floats ◽

China Sea ◽

Regional Ocean Model System ◽

Regional Ocean Model

AbstractPrevious studies are mainly limited to temperature and salinity (T/S) profiling data assimilation, while data assimilation based on Argo float trajectory information has received less research focus. In this study, a new method was proposed to assimilate Argo trajectory data: the middepth (indicates the parking depth of Argo floats in this study, ~1200 m) velocities are estimated from Argo trajectories and subsequently assimilated into the Regional Ocean Model System (ROMS) using four-dimensional variational data assimilation (4DVAR) method. This method can avoid a complicated float trajectory model in direct position assimilation. The 2-month assimilation experiments in South China Sea (SCS) showed that this proposed method can effectively assimilate Argo trajectory information into the model and improve middepth velocity field by adjusting the unbalanced component in the velocity increments. The assimilation of the Argo trajectory-derived middepth velocity with other observations (satellite observations and T/S profiling data) together yielded the best performance, and the velocity fields at the float parking depth are more consistent with the Argo float trajectories. In addition, this method will not decrease the assimilation performance of other observations [i.e., sea level anomaly (SLA), sea surface temperature (SST), and T/S profiles], which is indicative of compatibility with other observations in the 4DVAR assimilation system.

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АПВЕЛЛИНГ НА УЗКОМ ШЕЛЬФЕ ЯПОНСКОГО МОРЯ В 2011 Г., "Фундаментальная и прикладная гидрофизика"

Фундаментальная и прикладная гидрофизика ◽

10.7868/s2073667321010032 ◽

2021 ◽

pp. 31-42

Author(s):

А.В. Кошелева ◽

И.О. Ярощук ◽

Ф.Ф. Храпченков ◽

A. A. Pivovarov ◽

А.Н. Самченко ◽

...

Keyword(s):

Ocean Model ◽

Model System ◽

Regional Ocean Model System ◽

Regional Ocean Model

На основе инструментальных и спутниковых наблюдений рассматриваются характерные особенности локального апвеллинга, наблюдавшегося в октябре 2011 г. в юго-западной части залива Петра Великого Японского моря. Кроме того, приведены результаты численного моделирования, выполнявшегося при помощи Regional Ocean Model System (ROMS) со свободной поверхностью. При вычислениях использовались метеорологические наблюдения за неоднородностями поля ветра и инструментальные измерения гидрологической структуры воды. Анализ данных натурных измерений и их сравнение с результатами моделирования развития апвеллинга выявили, что пространственный и временной масштаб явления определялся силой, продолжительностью и направлением воздействующего ветра. Неоднородность поля скорости ветра, тесно связанная с особенностями береговой орографии, приводит к усилению апвеллинга у некоторых частей побережья и формированию температурных фронтов и струй холодной воды, поперечных основному течению, идущему вдоль шельфа.

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Demonstrating the potential of Regional Ocean Model System in simulating the upper ocean characteristic over Arabian Sea: impact of horizontal resolution

10.21203/rs.3.rs-792515/v1 ◽

2021 ◽

Author(s):

Prabha Kushwaha ◽

Vivek Kumar Pandey

Keyword(s):

Arabian Sea ◽

Horizontal Resolution ◽

Ocean Model ◽

Model System ◽

Sea Surface ◽

Sea Surface Salinity ◽

Surface Salinity ◽

Regional Ocean Model System ◽

Regional Ocean Model ◽

The Impact

Abstract This study attempted to demonstrate the skill of the regional ocean model system (ROMS) is simulating the hydrographic property of the Arabian Sea (AS). Additionally, the impact of horizontal resolution is investigated. In this regard, ROMS is integrated over AS covering [30˚E-80˚E; 5˚N-30N˚] at two different horizontal resolutions 1/6˚(~ 17km) and 1/4˚(~ 25km) for ten years. The comparison of model results with available observation and reanalysis indicates reasonable resemblances in reproducing the spatial-temporal distribution of surface and subsurface hydrographic property i.e. sea surface temperature (SST), sea surface salinity (SSS), sea surface currents, and subsurface temperature and salinity at both resolutions. The increasing resolution shows minimal improvement, indicating the fact that its not always guaranty to enhance the performance towards increasing resolution for every aspect.

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A REGIONAL STUDY OF THE BRAZILIAN SHELF/SLOPE CIRCULATION (13◦-31◦S) USING CLIMATOLOGICAL OPEN BOUNDARIES

Brazilian Journal of Geophysics ◽

10.22564/rbgf.v31i2.295 ◽

2013 ◽

Vol 31 (2) ◽

pp. 289 ◽

Cited By ~ 3

Author(s):

Janini Pereira ◽

Mauro Cirano ◽

Martinho Marta Almeida ◽

Fabiola Negreiros Amorim

Keyword(s):

Ocean Model ◽

Model System ◽

Western Boundary ◽

Data Set ◽

Western Boundary Currents ◽

Ocean Climate ◽

Boundary Currents ◽

Regional Ocean Model System ◽

Shelf Slope ◽

Regional Ocean Model

ABSTRACT. The oceanic features in the eastern and southeastern Brazilian shelf/slope between 13◦-31◦S are investigated using ROMS (Regional Ocean Model System). The model was integrated for 9 years and it was forced with: i) 6-hourly synoptic atmospheric data from NCEP; ii) initial and boundary conditions from OCCAM (Ocean Climate Circulation Advanced Modelling) monthly mean climatology and iii) tidal forcing from TPXO 7.1 global data set. The model results were compared with observations, which consisted in thermodynamic MDL (Mixed Layer Depth) climatology, satellite data, measurements from tide gauges along the shelf and currents measurements values from literature. The simulated currents represented the BC (Brazil Current)-IWBC (Intermediate Western Boundary Current) System. The BC-IWBC system at 22◦S cross-shelf section represents our simulation capability of reproducing the western boundary currents, it showed poleward BC and a opposing IWBC. At this section, the BC velocity core is in 50 m with 0.41 m.s− 1 and the IWBC core around 800 m with 0.15 m.s− 1. Keywords: Western South Atlantic, ROMS, Western Boundary Currents. RESUMO. A circulação oceânica na região da plataforma/talude do Brasil de 13◦-31◦S é investigada utilizando o modelo ROMS (Regional Ocean Model System). O modelo foi integrado por 9 anos e forçado com: i) dados atmosféricos sinótico a cada 6 horas do NCEP; ii) condições iniciais e laterais provenientes da climatologia mensal do modelo global OCCAM (Ocean Climate Circulation Advanced Modelling) e iii) forçamento de maré do modelo global TPXO 7.1. Os resultados do modelo foram comparados com observações, estas consistem em dados da profundidade da camada de mistura climatológica, dados de satélite, medições de marégrafos ao longo da plataforma e valores de medições de correntes disponíveis na literatura. As correntes simuladas representaram o sistema da CB (Corrente do Brasil)-CCI (Corrente de Contorno Intermediária). O sistema CB-CCI na seção normal a costa em 22◦S representou a capacidade de simulação das correntes de contorno oeste, mostrando a inversão de direção das duas correntes. Nesta seção, o núcleo de velocidade da CB em 50 m apresentou valores de 0,41 m.s− 1 e o núcleo da CCI em 800 m apresentou velocidade de 0,15 m.s− 1. Palavras-chave: Sudoeste do Atlântico, ROMS, Correntes de Contorno Oeste.

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Application of HY-2 Satellite SST Data in 4D Variational Assimilation Ocean Forecast Model

International Journal of Distributed Systems and Technologies ◽

10.4018/ijdst.2017040102 ◽

2017 ◽

Vol 8 (2) ◽

pp. 15-26

Author(s):

Zhenchang Zhang ◽

Libin Gao ◽

Minquan Guo ◽

Riqing Chen

Keyword(s):

Time Window ◽

Forecast Model ◽

Ocean Model ◽

Satellite Sst ◽

Regional Ocean Model System ◽

Model Research ◽

Numerical Ocean Model ◽

Regional Ocean Model ◽

Taiwan Straits ◽

Marine Environmental

The 4D variational (4DVAR) assimilation numerical ocean model research is proposed. This model for Taiwan Straits (TWS) is based on Regional Ocean Model System (ROMS). The background of the 4DVAR method is introduced and the development process of assimilation system is presented. In the present research, the model assimilated with Sea Surface Temperature (SST) data of HY-2 satellite (Qi, 2012; Xu, 2013) which is the first marine environmental monitoring satellite of China. In this paper, the model processes from Feb. 1 to Feb. 7, 2014 with one-day assimilation time window and root mean square error (RMSE) reduces averagely by 14.7%.

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Monsoon-Induced Surge during High Tides at the Southeast Coast of Vietnam: A Numerical Modeling Study

Geosciences ◽

10.3390/geosciences9020072 ◽

2019 ◽

Vol 9 (2) ◽

pp. 72 ◽

Cited By ~ 1

Author(s):

Nguyen Thuy ◽

Tran Tien ◽

Cecilie Wettre ◽

Lars Hole

Keyword(s):

Spring Tide ◽

Ocean Model ◽

Clear Trend ◽

Astronomical Tide ◽

Southeast Coast ◽

Regional Ocean Model System ◽

Operational Forecasts ◽

Regional Ocean Model ◽

Coast Of Vietnam ◽

Total Water Level

In this study, monsoon-induced surge during high tides at the Southeast coast of Vietnam was analyzed based on the observed tide data at the Vung Tau station in the period between 1997—2016. Specifically, the surge was determined by removing the astronomical tide from the observed total water level. The two-dimensional Regional Ocean Model System (ROMS 2D) was applied to simulate the surge induced by monsoons during spring tide. The surge observations showed that the change of peak surge did not follow a clear trend, of either an increase or decrease, over time. A peak surge of over 40 cm appeared mainly in October and November, although the peak of the astronomical tide was higher in December. ROMS 2D was validated with the observational data, and the model could sufficiently reproduce the wind-induced surge during high tides. This study therefor ere commends for ROMS 2D to be used in operational forecasts in this area.

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Dense CTD survey versus glider fleet sampling: comparing data assimilation performance in a regional ocean model west of Sardinia

Ocean Science ◽

10.5194/os-14-1069-2018 ◽

2018 ◽

Vol 14 (5) ◽

pp. 1069-1084 ◽

Cited By ~ 6

Author(s):

Jaime Hernandez-Lasheras ◽

Baptiste Mourre

Keyword(s):

Data Assimilation ◽

Large Scale ◽

Forecast Error ◽

Model Error ◽

Western Mediterranean ◽

Ocean Model ◽

Optimal Interpolation ◽

Trial Duration ◽

Sea Trial ◽

Regional Ocean Model

Abstract. The REP14-MED sea trial carried out off the west coast of Sardinia in June 2014 provided a rich set of observations from both ship-based conductivity–temperature–depth (CTD) probes and a fleet of underwater gliders. We present the results of several simulations assimilating data either from CTDs or from different subsets of glider data, including up to eight vehicles, in addition to satellite sea level anomalies, surface temperature and Argo profiles. The Western Mediterranean OPerational forcasting system (WMOP) regional ocean model is used with a local multi-model ensemble optimal interpolation scheme to recursively ingest both lower-resolution large-scale and dense local observations over the whole sea trial duration. Results show the capacity of the system to ingest both types of data, leading to improvements in the representation of all assimilated variables. These improvements persist during the 3-day periods separating two analyses. At the same time, the system presents some limitations in properly representing the smaller-scale structures, which are smoothed out by the model error covariances provided by the ensemble. An evaluation of the forecasts using independent measurements from shipborne CTDs and a towed ScanFish deployed at the end of the sea trial shows that the simulations assimilating initial CTD data reduce the error by 39 % on average with respect to the simulation without data assimilation. In the glider-data-assimilative experiments, the forecast error is reduced as the number of vehicles increases. The simulation assimilating CTDs outperforms the simulations assimilating data from one to four gliders. A fleet of eight gliders provides similar performance to the 10 km spaced CTD initialization survey in these experiments, with an overall 40 % model error reduction capacity with respect to the simulation without data assimilation when comparing against independent campaign observations.

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Tidal effects on ichthyoplankton aggregation and dispersion in the Southern Gulf of Mexico

Brazilian Journal of Oceanography ◽

10.1590/s1679-87592013000400004 ◽

2013 ◽

Vol 61 (4) ◽

pp. 231-241 ◽

Cited By ~ 1

Author(s):

María Adela Monreal Gómez ◽

David Alberto Salas de León ◽

Cesar Flores Coto ◽

Fernando Flores Hernández ◽

David Salas Monreal ◽

...

Keyword(s):

Gulf Of Mexico ◽

Single Point ◽

Internal Tide ◽

Ocean Model ◽

Hydraulic Control ◽

Barotropic Tide ◽

Regional Ocean Model System ◽

Southern Gulf Of Mexico ◽

Regional Ocean Model

The role of vertical barotropic and baroclinic tidal forcing in the aggregation and dispersion of ichthyoplankton in the Southern Gulf of Mexico was analyzed in this study. Samplings of ichthyoplankton and the determination of hydrographic parameters were performed during September 1992 at a single point of 180 m depth, near the shelf break (19º32'N - 92º38.5'W). A 24 h CTD yo-yoing casting and biological samples were taken every 2 h and these measurements were combined with water velocity and density simulations from the Regional Ocean Model System (ROMS). One thermocline and two haloclines were depicted. The Froude number increased with a 2 h lag with respect to the maximal barotropic tide, suggesting the existence of a baroclinic tide. Aggregation and dispersion of the ichthyoplankton showed vertical oscillations in the abundance and the numbers of taxa and larvae with a 5 h lag with respect to the maximal barotropic tide and were in phase with the thermocline oscillation. The vertical oscillation was attributed to a hydraulic control forced by the internal tide.

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