Comments to the manuscript titled "A High-resolution Biogeochemical Model (ROMS 3.4 + bio_Fennel) of the East Australian Current System"

Abstract. Understanding phytoplankton dynamics is critical across a range of topics, spanning from fishery management to climate change mitigation. It is particularly interesting in the East Australian Current (EAC) system, as the region's eddy field strongly conditions nutrient availability and therefore phytoplankton growth. Numerical models provide unparalleled insight into these biogeochemical dynamics. Yet, to date, modelling efforts off southeastern Australia have either targeted case studies (small spatial and temporal scales) or encompassed the whole EAC system but focused on climate change effects at the mesoscale (with a spatial resolution of 1/10∘). Here we couple a model of the pelagic nitrogen cycle (bio_Fennel) to a 10-year high-resolution (2.5–5 km horizontal) three-dimensional ocean model (ROMS) to resolve both regional and finer-scale biogeochemical processes occurring in the EAC system. We use several statistical metrics to compare the simulated surface chlorophyll to an ocean colour dataset (Copernicus-GlobColour) for the 2003–2011 period and show that the model can reproduce the observed phytoplankton surface patterns with a domain-wide RMSE of approximately 0.2 mg Chl a m−3 and a correlation coefficient of 0.76. This coupled configuration will provide a much-needed framework to examine phytoplankton variability in the EAC system providing insight into important ecosystem dynamics such as regional nutrient supply mechanisms and biogeochemical cycling occurring in EAC eddies.

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A High-resolution Biogeochemical Model (ROMS 3.4 + bio_Fennel) of the East Australian Current System

10.5194/gmd-2018-187 ◽

2018 ◽

Author(s):

Carlos Rocha ◽

Christopher A. Edwards ◽

Moninya Roughan ◽

Paulina Cetina-Heredia ◽

Colette Kerry

Keyword(s):

Climate Change ◽

High Resolution ◽

Numerical Models ◽

Current System ◽

Ocean Model ◽

Ecosystem Dynamics ◽

Biogeochemical Model ◽

East Australian Current ◽

Surface Patterns ◽

Insight Into

Abstract. Understanding phytoplankton dynamics is critical across a range of topics, spanning from fisheries management to climate change mitigation. It is particularly interesting in the East Australian Current (EAC) System, as the region’s eddy field strongly conditions nutrient availability and, therefore, phytoplankton growth. Numerical models provide unparalleled insight into these biogeochemical dynamics. Yet, to date, modelling efforts off southeastern Australia have either targeted case studies (small spatial and temporal scales) or encompassed the whole EAC System but focused on climate change effects at the mesoscale (with a spatial resolution of 1/10º). Here we couple a model of the pelagic nitrogen cycle (bio_Fennel) to a 10-year high-resolution (2.5–5 km horizontal) three-dimensional ocean model (ROMS) to resolve both regional and finer scale biogeochemical processes occurring in the EAC System. We use several statistical metrics to compare the simulated surface chlorophyll to an ocean colour dataset (Copernicus-GlobColour) for the 2003–2011 period and show that the model can reproduce the observed phytoplankton surface patterns with a domain-wide rmse of approximately 0.2 mg chla m−3 and a correlation coefficient of 0.76. This coupled configuration will provide a much-needed framework to examine phytoplankton variability in the EAC System providing insight into important ecosystem dynamics such as regional nutrient supply mechanisms and biogeochemical cycling occurring in EAC eddies.

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The Physical Structure and Behavior of the California Current System

10.1101/2020.02.10.942730 ◽

2020 ◽

Cited By ~ 2

Author(s):

Lionel Renault ◽

James C. McWilliams ◽

Alexandre Jousse ◽

Curtis Deutsch ◽

Hartmut Frenzel ◽

...

Keyword(s):

High Resolution ◽

Boundary Conditions ◽

Current System ◽

Mesoscale Eddy ◽

California Current ◽

Open Boundary ◽

Biogeochemical Model ◽

California Current System ◽

Synoptic Wind ◽

The Impact

AbstractThis paper is the first of two that present a 16-year reanalysis solution from a coupled physical and biogeochemical model of the California Current System (CCS) along the U. S. West Coast and validate the solution with respect to mean and seasonal fields and, to a lesser degree, eddy variability. Its companion paper is Deutsch et al. (2019a). The intent is to construct and demonstrate a modeling tool that will be used for mechanistic explanations, attributive causal assessments, and forecasts of future evolution for circulation and biogeochemistry, with particular attention to the increasing oceanic stratification, deoxygenation, and acidification. A well-resolved mesoscale (dx = 4 km) simulation of the CCS circulation is made with the Regional Oceanic Modeling System over a reanalysis period of 16 years from 1995 to 2010. The oceanic solution is forced by a high-resolution (dx = 6 km) regional configuration of the Weather and Research Forecast (WRF) atmospheric model. Both of these high-resolution regional oceanic and atmospheric simulations are forced by lateral open boundary conditions taken from larger-domain, coarser-resolution parent simulations that themselves have boundary conditions from the Mercator and Climate Forecast System reanalyses, respectively. We first show good agreement between the simulated atmospheric forcing of the ocean and satellite observations for the spatial patterns and seasonal variability of the cloud cover and for the surface fluxes of momentum, heat, and freshwater. The simulated oceanic physical fields are then evaluated with satellite and in situ observations. The simulation reproduces the main structure of the climatological upwelling front and cross-shore isopycnal slopes, the mean current patterns (including the California Undercurrent), and the seasonal and interannual variability. It also shows agreement between the mesoscale eddy activity and the wind-work energy exchange between the ocean and atmosphere modulated by influences of surface current on surface stress. Finally, the impact of using a high frequency wind forcing is assessed for the importance of synoptic wind variability to realistically represent oceanic mesoscale activity and ageostrophic inertial currents.

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High-Resolution Atmospheric Sensing of Multiple Atmospheric Variables Using the DataHawk Small Airborne Measurement System

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-d-12-00089.1 ◽

2013 ◽

Vol 30 (10) ◽

pp. 2352-2366 ◽

Cited By ~ 40

Author(s):

Dale A. Lawrence ◽

Ben B. Balsley

Keyword(s):

High Resolution ◽

Measurement System ◽

Current System ◽

Low Cost ◽

Structure Constant ◽

Turbulence Structure ◽

Quality Of Data ◽

Airborne Measurement ◽

Atmospheric Measurement ◽

Atmospheric Variables

Abstract The DataHawk small airborne measurement system provides in situ atmospheric measurement capabilities for documenting scales as small as 1 m and can access reasonably large volumes in and above the atmospheric boundary layer at low cost. The design of the DataHawk system is described, beginning with the atmospheric measurement requirements, and articulating five key challenges that any practical measurement system must overcome. The resulting characteristics of the airborne and ground support components of the DataHawk system are outlined, along with its deployment, operating, and recovery modes. Typical results are presented to illustrate the types and quality of data provided by the current system, as well as the need for more of these finescale measurements. Particular focus is given to the DataHawk's ability to make very-high-resolution measurements of a variety of atmospheric variables simultaneously, with emphasis given to the measurement of two important finescale turbulence parameters, (the temperature turbulence structure constant) and ɛ (the turbulent energy dissipation rate). Future sensing possibilities and limitations using this approach are also discussed.

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Development and evaluation of a high-resolution reanalysis of the East Australian Current region using the Regional Ocean Modelling System (ROMS 3.4) and Incremental Strong-Constraint 4-Dimensional Variational (IS4D-Var) data assimilation

Geoscientific Model Development ◽

10.5194/gmd-9-3779-2016 ◽

2016 ◽

Vol 9 (10) ◽

pp. 3779-3801 ◽

Cited By ~ 21

Author(s):

Colette Kerry ◽

Brian Powell ◽

Moninya Roughan ◽

Peter Oke

Keyword(s):

High Resolution ◽

Data Assimilation ◽

Water Column ◽

Marked Improvement ◽

Sea Surface ◽

East Australian Current ◽

Strong Constraint ◽

Ocean Modelling ◽

Model Dynamics ◽

Modelling System

Abstract. As with other Western Boundary Currents globally, the East Australian Current (EAC) is highly variable making it a challenge to model and predict. For the EAC region, we combine a high-resolution state-of-the-art numerical ocean model with a variety of traditional and newly available observations using an advanced variational data assimilation scheme. The numerical model is configured using the Regional Ocean Modelling System (ROMS 3.4) and takes boundary forcing from the BlueLink ReANalysis (BRAN3). For the data assimilation, we use an Incremental Strong-Constraint 4-Dimensional Variational (IS4D-Var) scheme, which uses the model dynamics to perturb the initial conditions, atmospheric forcing, and boundary conditions, such that the modelled ocean state better fits and is in balance with the observations. This paper describes the data assimilative model configuration that achieves a significant reduction of the difference between the modelled solution and the observations to give a dynamically consistent “best estimate” of the ocean state over a 2-year period. The reanalysis is shown to represent both assimilated and non-assimilated observations well. It achieves mean spatially averaged root mean squared (rms) residuals with the observations of 7.6 cm for sea surface height (SSH) and 0.4 °C for sea surface temperature (SST) over the assimilation period. The time-mean rms residual for subsurface temperature measured by Argo floats is a maximum of 0.9 °C between water depths of 100 and 300 m and smaller throughout the rest of the water column. Velocities at several offshore and continental shelf moorings are well represented in the reanalysis with complex correlations between 0.8 and 1 for all observations in the upper 500 m. Surface radial velocities from a high-frequency radar array are assimilated and the reanalysis provides surface velocity estimates with complex correlations with observed velocities of 0.8–1 across the radar footprint. A comparison with independent (non-assimilated) shipboard conductivity temperature depth (CTD) cast observations shows a marked improvement in the representation of the subsurface ocean in the reanalysis, with the rms residual in potential density reduced to about half of the residual with the free-running model in the upper eddy-influenced part of the water column. This shows that information is successfully propagated from observed variables to unobserved regions as the assimilation system uses the model dynamics to adjust the model state estimate. This is the first study to generate a reanalysis of the region at such a high resolution, making use of an unprecedented observational data set and using an assimilation method that uses the time-evolving model physics to adjust the model in a dynamically consistent way. As such, the reanalysis potentially represents a marked improvement in our ability to capture important circulation dynamics in the EAC. The reanalysis is being used to study EAC dynamics, observation impact in state-estimation, and as forcing for a variety of downscaling studies.

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Rip current evidence by hydrodynamic simulations, bathymetric surveys and UAV observation

10.5194/nhess-2017-53 ◽

2017 ◽

Cited By ~ 1

Author(s):

Guido Benassai ◽

Pietro Aucelli ◽

Giorgio Budillon ◽

Massimo De Stefano ◽

Diana Di Luccio ◽

...

Keyword(s):

Grain Size ◽

High Resolution ◽

Numerical Simulations ◽

Current System ◽

Current Evidence ◽

Rip Current ◽

Rip Currents ◽

Transport Pathways ◽

Fine Sediments ◽

Scientific Challenge

Abstract. The prediction of the formation, spacing and location of rip currents is a scientific challenge that can be achieved by means of different complementary methods. In this paper the analysis of numerical and experimental data, including UAV observation, allowed to detect the presence of rip currents and rip channels at the mouth of Sele river, in the Gulf of Salerno, southern Italy. The dataset used to analyze these phenomena consisted of two different bathymetric surveys, a detailed sediment 5 analysis and a set of high-resolution wave numerical simulations, completed with satellite and UAV observation. The grain size trend analysis and the numerical simulations allowed to identify the rip current system, forced by topographically constrained channels incised on the seabed, which were detected by high resolution bathymetric surveys. The study evidenced that on the coastal area of the Sele mouth grain-size trends are controlled by the contribution of fine sediments, which exhibit suspended transport pathways due to rip currents and longshore currents. The results obtained were confirmed by satellite and UAV 10 observations in different years.

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Observation Impact in a Regional Reanalysis of the East Australian Current System

Journal of Geophysical Research Oceans ◽

10.1029/2017jc013685 ◽

2018 ◽

Vol 123 (10) ◽

pp. 7511-7528 ◽

Cited By ~ 10

Author(s):

Colette Kerry ◽

Moninya Roughan ◽

Brian Powell

Keyword(s):

Current System ◽

East Australian Current ◽

Observation Impact ◽

Regional Reanalysis

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The INALT family – a set of high-resolution nests for the Agulhas Current system within global NEMO ocean/sea-ice configurations

Geoscientific Model Development ◽

10.5194/gmd-12-3329-2019 ◽

2019 ◽

Vol 12 (7) ◽

pp. 3329-3355 ◽

Cited By ~ 6

Author(s):

Franziska U. Schwarzkopf ◽

Arne Biastoch ◽

Claus W. Böning ◽

Jérôme Chanut ◽

Jonathan V. Durgadoo ◽

...

Keyword(s):

High Resolution ◽

Boundary Conditions ◽

Current System ◽

Western Boundary Current ◽

Global Ocean ◽

Western Boundary ◽

Boundary Current ◽

The South ◽

Agulhas Current ◽

Mesoscale Dynamics

Abstract. The Agulhas Current, the western boundary current of the South Indian Ocean, has been shown to play an important role in the connectivity between the Indian and Atlantic oceans. The greater Agulhas Current system is highly dominated by mesoscale dynamics. To investigate their influence on the regional and global circulations, a family of high-resolution ocean general circulation model configurations based on the NEMO code has been developed. Horizontal resolution refinement is achieved by embedding “nests” covering the South Atlantic and the western Indian oceans at 1/10∘ (INALT10) and 1/20∘ (INALT20) within global hosts with coarser resolutions. Nests and hosts are connected through two-way interaction, allowing the nests not only to receive boundary conditions from their respective host but also to feed back the impact of regional dynamics onto the global ocean. A double-nested configuration at 1/60∘ resolution (INALT60) has been developed to gain insights into submesoscale processes within the Agulhas Current system. Large-scale measures such as the Drake Passage transport and the strength of the Atlantic meridional overturning circulation are rather robust among the different configurations, indicating the important role of the hosts in providing a consistent embedment of the regionally refined grids into the global circulation. The dynamics of the Agulhas Current system strongly depend on the representation of mesoscale processes. Both the southward-flowing Agulhas Current and the northward-flowing Agulhas Undercurrent increase in strength with increasing resolution towards more realistic values, which suggests the importance of improving mesoscale dynamics as well as bathymetric slopes along this narrow western boundary current regime. The exploration of numerical choices such as lateral boundary conditions and details of the implementation of surface wind stress forcing demonstrates the range of solutions within any given configuration.

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