Eric Chassignet - Academia.edu (original) (raw)

Papers by Eric Chassignet

Journal of Operational Oceanography, Aug 18, 2015

The availability of GODAE Oceanview-type ocean forecast systems provides the opportunity to devel... more The availability of GODAE Oceanview-type ocean forecast systems provides the opportunity to develop high-resolution, short-to medium-range coupled prediction systems. Several groups have undertaken the first experiments based on relatively unsophisticated approaches. Progress is being driven at the institutional level targeting a range of applications that represent their respective national interests with clear overlaps and opportunities for information exchange and collaboration. The applications include forecasting of the general circulation, hurricanes, extra-tropical storms, highlatitude weather and coastal air-sea interaction. In some cases, research has moved beyond case and sensitivity studies to controlled experiments to obtain statistically significant metrics and operational predictions.

HAL (Le Centre pour la Communication Scientifique Directe), 2002

The ocean numerical model is one of the three essential components of an ocean forecasting system... more The ocean numerical model is one of the three essential components of an ocean forecasting system. Observational data, via data assimilation, set the stage for the model forecast. The quality of the forecast will primarily depend on the ability of the ocean numerical model to faithfully represent the ocean physics and dynamics. Even the use of an infinite amount of data to constrain the initial conditions will not necessarily improve the forecast against persistence of a poorly performing ocean numerical model. In this paper, we briefly review the present state of the art of numerical models within the context of operational global ocean prediction systems, discuss their limitations, and present some of the challenges associated with global ocean modeling. We also briefly address how ocean model development can benefit from such operational systems.

This document contains supplemental materials of the paper by Tsujino et al. "Evaluation of globa... more This document contains supplemental materials of the paper by Tsujino et al. "Evaluation of global ocean-sea-ice model simulations based on the experimental protocols of the Ocean Model Intercomparison Project phase 2 (OMIP-2)" submitted for possible publication in Geoscientific Model Development.

Ocean Modelling, Mar 1, 2016

The Arctic Ocean simulated in fourteen global ocean-sea ice models in the framework of the Coordi... more The Arctic Ocean simulated in fourteen global ocean-sea ice models in the framework of the Coordinated Ocean-ice Reference Experiments, phase II (CORE II) is analyzed. The focus is on the Arctic sea ice extent, the solid freshwater (FW) sources and solid freshwater content (FWC). Available observations are used for model evaluation. The variability of sea ice extent and solid FW budget is more consistently reproduced than their mean state in the models. The descending trend of September sea ice extent is well simulated in terms of the model ensemble mean. Models overestimating sea ice thickness tend to underestimate the descending trend of September sea ice extent. The models underestimate the observed sea ice thinning trend by a factor of two. When averaged on decadal time scales, the variation of Arctic solid FWC is contributed by those of both sea ice production and sea ice transport, which are out of phase in time. The solid FWC decreased in the recent decades, caused mainly by the reduction in sea ice thickness. The models did not simulate the acceleration of sea ice thickness decline, leading to an underestimation of solid FWC trend after 2000. The common model behaviour, including the tendency to underestimate the trend of sea ice thickness and March sea ice extent, remains to be improved. 1. Arctic sea ice extent and solid freshwater in 14 CORE-II models are inter-compared 2. The models better represent the variability than the mean state 3. The September ice extent trend is reasonably represented by the model ensemble mean 4. The descending trend of ice thickness is underestimated compared to observations 5. The models underestimate the reduction in solid freshwater content in recent years *Highlights (for review)

Geoscientific Model Development, Aug 21, 2020

We present a new framework for global oceansea-ice model simulations based on phase 2 of the Ocea... more We present a new framework for global oceansea-ice model simulations based on phase 2 of the Ocean Model Intercomparison Project (OMIP-2), making use of the surface dataset based on the Japanese 55-year atmospheric reanalysis for driving ocean-sea-ice models (JRA55-do). We motivate the use of OMIP-2 over the framework for the first phase of OMIP (OMIP-1), previously referred to as the Coordinated Ocean-ice Reference Experiments (COREs), via the evaluation of OMIP-1 and OMIP-2 simulations from 11 state-of-the-science global ocean-sea-ice models. In the present evaluation, multi-model ensemble means and spreads are calculated separately for the OMIP-1 and OMIP-2 simulations and overall performance is assessed considering metrics commonly used by ocean modelers. Both OMIP-1 and Published by Copernicus Publications on behalf of the European Geosciences Union.

Ocean Modelling, Apr 1, 2016

and volume transports through the Fram Strait and the Barents Sea Opening. The models agree more ... more and volume transports through the Fram Strait and the Barents Sea Opening. The models agree more on the decadal variability, to a large degree dictated by the common atmospheric forcing. We conclude that the CORE-II model study helps us to understand the crucial biases in the Arctic Ocean. The current coarse resolution state-of-the-art ocean models need to be improved in accurate representation of the Atlantic Water inflow into the Arctic and density currents coming from the shelves.

Frontiers in Marine Science, Feb 26, 2019

Cambridge University Press eBooks, Apr 5, 2012

2005 Users Group Conference (DOD-UGC'05), Jun 27, 2005

OWGIS version 2.0 is an open source Java and JavaScript application that builds easily configurab... more OWGIS version 2.0 is an open source Java and JavaScript application that builds easily configurable Web GIS sites for desktop and mobile devices. This version of OWGIS generates mobile interfaces based on HTML5 technology and can be used to create mobile applications. The style of the generated websites is modified using COMPASS, a well known CSS Authoring Framework. In addition, OWGIS uses several Open Geospatial Consortium standards to request data from the most common map servers, such as GeoServer. It is also able to request data from ncWMS servers allowing the display of 4D data from NetCDF files. This application is configured by XML files that define which layers, geographic datasets, are displayed on the Web GIS sites. Among other features, OWGIS allows for animations; vertical profiles and vertical transects; different color palettes; dynamic maps; the ability to download data, and display text in multiple languages. OWGIS users are mainly scientists in the oceanography, meteorology and climate fields.

Journal of Marine Research, Nov 1, 2014

The Florida Big Bend region in the northeastern Gulf of Mexico contains both spawning sites and n... more The Florida Big Bend region in the northeastern Gulf of Mexico contains both spawning sites and nursery habitats for a variety of economically valuable marine species. One species, the gag grouper (Mycteroperca microlepis), relies on the shelf circulation to distribute larvae from shelf-break spawning grounds to coastal sea-grass nurseries each spring. Therefore, identifying the dominant circulation features and physical mechanisms that contribute to cross-shelf transport during the springtime is a necessary step in understanding the variation of the abundance of this reef fish. The mean circulation features and onshore transport pathways are investigated using a numerical ocean model with very high horizontal resolution (800-900 m) over the period 2004-2010. The model simulation demonstrates that the mean springtime shelf circulation patterns are set primarily by flow during periods of southeastward or northwestward wind stress, and that significant cross-shelf flow is generated during southeastward winds. Lagrangian particle tracking experiments demonstrate that a primary pathway exists south of Apalachicola Bay by which particles are able to reach inshore, and that significantly more particles arrive inshore when they originate from an area adjacent to a known gag spawning aggregation site. The results provide, for the first time, a description of the pathways by which onshore transport is possible from gag spawning sites at the shelf break to sea-grass nurseries at the coast in the Florida Big Bend.

AGU Fall Meeting Abstracts, Dec 1, 2016

&lt;p&gt;The purpose of employing data assimilation methods in operational ocean ... more &lt;p&gt;The purpose of employing data assimilation methods in operational ocean forecasting systems is to provide good initialization to the models and is dependent on good quality ocean observations being assimilated. Using or accepting erroneous data can result in an inaccurate analysis and alternatively, rejecting extreme or valid data can result in missing important events.&lt;/p&gt;&lt;p&gt;In this study two ocean-sea ice coupled systems are considered: HYCOM-CICE4 and MOM6-CICE6 at &amp;#188;-deg horizontal resolution and 41 vertical layers. The two coupled models are initialized from the World Ocean Atlas 2018 (WOA) temperature and salinity climatology for a period of 20 years. Both models are forced with GEFS (Global Ensemble Forecast System created by the National Centers for Environmental Prediction: NCEP). The data assimilation is performed on a 24-hr cycle using RTOFS-DA (Real-time Ocean Forecasting system-DA; 3DVAR) for HYCOM-CICE4 and SOCA (Sea ice Ocean Coupled Assimilation; 3DVAR) for MOM6-CICE6 to compare the data Quality Control (QC) methods. The ocean data being assimilated include satellite sea surface temperature (SST) and sea surface salinity (SSS), in-situ temperature &amp; salinity, absolute dynamic topography (ADT), sea ice concentration.&lt;/p&gt;&lt;p&gt;The QC in RTOFS-DA and SOCA are fully automated and are performed through various filters applied (e.g., land-sea area fraction to eliminate satellite data near the coast, temperature inversion elimination in in-situ profile data, etc). The various QC methods in both DA systems are described. The results of the analysis and 24-forecast are compared against independent observations and statistics of the data accepted and rejected between the two DA systems are presented and discussed.&lt;/p&gt;

CMIP6 Forcing Datasets (input4MIPs): These data includes all datasets published for 'input4MI... more CMIP6 Forcing Datasets (input4MIPs): These data includes all datasets published for 'input4MIPs.CMIP6.OMIP.MRI.MRI-JRA55-do-1-3' according to the Data Reference Syntax defined as 'activity_id.mip_era.target_mip.institution_id.source_id.realm.frequency.variable_id.grid_label'. The model MRI-JRA55-do-1-3 (MRI JRA55-do 1.3: Atmospheric state generated for OMIP based on the JRA-55 reanalysis) was run by the Meteorological Research Institute, Tsukuba, Ibaraki 305-0052, Japan (MRI) in native nominal resolutions: unknown. Project: The forcing datasets (and boundary conditions) needed for CMIP6 experiments are being prepared by a number of different experts. Initially many of these datasets may only be available from those experts, but over time as part of the 'input4MIPs' activity most of them will be archived by PCMDI and served by the Earth System Grid Federation (https://esgf-node.llnl.gov/search/input4mips/ ). More information is available in the living document: http://goo.gl/r8up31 .

Journal of Plankton Research, 2021

Atlantic bluefin tuna (ABT) (Thunnus thynnus) travel long distances to spawn in oligotrophic regi... more Atlantic bluefin tuna (ABT) (Thunnus thynnus) travel long distances to spawn in oligotrophic regions of the Gulf of Mexico (GoM) which suggests these regions offer some unique benefit to offspring survival. To better understand how larval survival varies within the GoM a spatially explicit, Lagrangian, individual-based model was developed that simulates dispersal and mortality of ABT early life stages within realistic predator and prey fields during the spawning periods from 1993 to 2012. The model estimates that starvation is the largest cumulative source of mortality associated with an early critical period. However, elevated predation on older larvae is identified as the main factor limiting survival to late postflexion. As a result, first-feeding larvae have higher survival on the shelf where food is abundant, whereas older larvae have higher survival in the open ocean with fewer predators, making the shelf break an optimal spawning area. The modeling framework developed in this...

Journal of Physical Oceanography, 2020

Three simulations of the circulation in the Gulf of Mexico (the “Gulf”) using different numerical... more Three simulations of the circulation in the Gulf of Mexico (the “Gulf”) using different numerical general circulation models are compared with results of recent large-scale observational campaigns conducted throughout the deep (>1500 m) Gulf. Analyses of these observations have provided new understanding of large-scale mean circulation features and variability throughout the deep Gulf. Important features include cyclonic flow along the continental slope, deep cyclonic circulation in the western Gulf, a counterrotating pair of cells under the Loop Current region, and a cyclonic cell to the south of this pair. These dominant circulation features are represented in each of the ocean model simulations, although with some obvious differences. A striking difference between all the models and the observations is that the simulated deep eddy kinetic energy under the Loop Current region is generally less than one-half of that computed from observations. A multidecadal integration of one o...

Zooplankton play an important role in global biogeochemistry, and their secondary production supp... more Zooplankton play an important role in global biogeochemistry, and their secondary production supports valuable fisheries of the world's oceans. Currently, zooplankton standing stocks cannot be estimated using remote sensing techniques. Hence, coupled physical-biogeochemical models (PBMs) provide an important tool for studying zooplankton on regional and global scales. However, evaluating the accuracy of zooplankton biomass estimates from PBMs has been a major challenge due to sparse observations. In this study, we configure a PBM for the Gulf of Mexico (GoM) from 1993 to 2012 and validate the model against an extensive combination of biomass and rate measurements. Spatial variability in a multidecadal database of mesozooplankton biomass for the northern GoM is well resolved by the model with a statistically significant (p < 0.01) correlation of 0.90. Mesozooplankton secondary production for the region averaged 66 ± 8 × 10 9 kg C yr −1 , equivalent to ∼ 10 % of net primary production (NPP), and ranged from 51 to 82 × 10 9 kg C yr −1 , with higher secondary production inside cyclonic eddies and substantially reduced secondary production in anticyclonic eddies. Model results from the shelf regions suggest that herbivory is the dominant feeding mode for small mesozooplankton (< 1 mm), whereas larger mesozooplankton are primarily carnivorous. In open-ocean oligotrophic waters, however, both mesozooplankton groups show proportionally greater reliance on heterotrophic protists as a food source. This highlights an important role of microbial and protistan food webs in sustaining mesozooplankton biomass in the GoM, which serves as the primary food source for early life stages of many commercially important fish species, including tuna.

Quantifying the spatiotemporal variability in zooplankton dynamics in the Gulf of Mexico using a ... more Quantifying the spatiotemporal variability in zooplankton dynamics in the Gulf of Mexico using a physical-biogeochemical model S1 Biogeochemical model forcing, initial, and open boundary conditions Surface downward shortwave radiation fields provided by the National Centers for Environmental Prediction (NCEP) were used to estimate light limitation of phytoplankton in NEMURO-GoM. Specifically, Climate Forecast System Reanalysis (CFSR) hourly shortwave radiation fields were daily averaged and used to force the model from 1993 to 2010. CFSv2 fields were also daily averaged and used for the remaining two years of the simulation. Before use in the model both CFSR (~38km resolution) and CFSv2 (~34.5 km resolution) products were linearly interpolated to the NEMURO-GoM grid (~20 km) and subsequently scaled by a factor of 0.43 (default NEMURO parameter) to estimate photosynthetic active radiation (PAR) which is used directly in the SP and LP light limitation term to estimate phytoplankton growth rates. In total, the online H-GoM simulation that provided flow fields for NEMURO-GoM incorporated 37 independent rivers with climatological monthly averaged discharge. These same river locations and discharges were used along with nutrient measurements to prescribe riverine nutrient input in the offline NEMURO-GoM. Due to a lack of water quality data the same nutrient time series derived for the Mississippi River was prescribed for all rivers. Nutrient input associated with Mississippi river discharged into the GoM was approximated using data from United States Geological Survey (USGS) real-time streamflow and water quality analysis at station 07374000 (Baton Rouge, LA). Climatological daily averaged nitrate concentrations were derived from USGS samples collected from 2011 to 2017. The daily climatology was then use cyclically in NEMURO-GoM for all 20 years of the simulation. Silica river input was approximated using a constant Si:N ratio of 2.0. We found that adding additional sources of nitrogen equivalent to 10% of the USGS daily nitrate concentration for the remaining four nutrient pools (i.e. NH, DON, PON, and OP) had no appreciable impact on the model.