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Author Wu, Z. ; Huang, N.E. ; Chen, X.
Title The Multi-Dimensional Ensemble Empirical Mode Decomposition Method Type $loc['typeJournal Article']
Year 2009 Publication Advances in Adaptive Data Analysis Abbreviated Journal Adv. Adapt. Data Anal.
Volume 01
Issue 03
Pages 339-372
Keywords Empirical mode decomposition (EMD) ; ensemble empirical mode decomposition (EEMD) ; minimal scale principle ; pseudo multi-dimensional ensemble empirical mode decomposition ; multi-dimensional ensemble empirical mode decomposition
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Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 1793-5369
ISBN Medium
Area Expedition Conference
Funding Approved $loc['no']
Call Number COAPS @ mfield @
Serial 669
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Author Xiaobiao Xu, Eric Chassignet
Title Subpolar-Subtropical Connectivity of the North Atlantic Circulation Type $loc['typeMiscellaneous']
Year 2019 Publication PHYSICAL OCEANOGRAPHY Abbreviated Journal
Volume Issue Pages
Keywords Warming, hydrographic, subtropical gyres, sub-basins, passive tracers
Abstract The ocean, through its large capacity to store heat, plays a critical role in Earth's climate and climate variability. Warming of the world's oceans since 1955 accounts for approximately 93% of the warming of the Earth system. However, this warming is neither spatially uniform nor temporally constant. Superimposed on the global long-term trend is climate variability on inter-annual to inter-decadal time scales and regional to basin scales. Satellite altimeters and hydrographic observations show that the North Atlantic, including the sub-polar region, has rapidly become warmer and saltier since the early 1990s. An emerging picture is that the most recent 20 years or so of warming in the North Atlantic represents, in part, a transition of the Atlantic multi-decadal variability pattern from a cold to a warm phase. These decadal climate transitions involve changes both laterally in the sub-tropical and sub-polar gyres of the North Atlantic and vertically in the Atlantic Meridional Overturning Circulation (AMOC), a key component of the global heat and freshwater circulation system. This study of the North Atlantic circulation concentrates on a transition region around the Grand Banks of Newfoundland, where the effects of boundary currents and jets, recirculations, and mesoscale eddies (length scales typically less than 100 km) are dominant. Strong interactions occur in this transition region, laterally between the subpolar and subtropical gyres and vertically between the cold and warm limbs of the Atlantic Meridional Circulation (AMOC). There is evidence that this relatively compact region plays a key role in altering and even modulating the AMOC over a much larger scale and thus is important for the long-term, decadal variability of the Atlantic Ocean. Yet, despite many observational field programs, the dynamics and impacts of this region are not well understood. The project will contribute to understanding the variability of the AMOC by addressing the connectivity of the sub-polar and the sub-tropical gyres. The results of this model-data synthesis will be of particular significance to coupled climate models, which are central to understanding and predicting global climate change. The educational/outreach components of this project will be focused on cultivating scientific literacy with regards to ocean climate research in K-12 schools, at the university level, and in the local community through a variety of online resources/interactive tools for educators, the Florida State University Young Scholars program for high school students, and the “Scientists in the Schools” program. Finally, the requested funding will support a junior faculty member and a graduate student who will be trained in ocean modeling, data analysis and interpretation.
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Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
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ISSN ISBN Medium
Area Expedition Conference
Funding Approved $loc['no']
Call Number COAPS @ user @
Serial 1018
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Author Xu, X. ; Bower, A. ; Furey, H. ; Chassignet, E.P.
Title Variability of the Iceland-Scotland Overflow Water Transport Through the Charlie-Gibbs Fracture Zone: Results From an Eddying Simulation and Observations Type $loc['typeJournal Article']
Year 2018 Publication Journal of Geophysical Research: Oceans Abbreviated Journal J. Geophys. Res. Oceans
Volume 123
Issue 8
Pages 5808-5823
Keywords Iceland ; Scotland overflow water ; Charlie ; Gibbs fracture zone ; variability ; volume transport ; eddying simulation
Abstract Observations show that the westward transport of the Iceland‐Scotland overflow water (ISOW) through the Charlie‐Gibbs Fracture Zone (CGFZ) is highly variable. This study examines (a) where this variability comes from and (b) how it is related to the variability of ISOW transport at upstream locations in the Iceland Basin and other ISOW flow pathways. The analyses are based on a 35‐year 1/12° eddying Atlantic simulation that represents well the main features of the observed ISOW in the area of interest, in particular, the transport variability through the CGFZ. The results show that (a) the variability of the ISOW transport is closely correlated with that of the barotropic transports in the CGFZ associated with the meridional displacement of the North Atlantic Current front and is possibly induced by fluctuations of large‐scale zonal wind stress in the Western European Basin east of the CGFZ; (b) the variability of the ISOW transport is increased by a factor of 3 from the northern part of the Iceland Basin to the CGFZ region and transport time series at these two locations are not correlated, further suggesting that the variability at the CGFZ does not come from the upstream source; and (c) the variability of the ISOW transport at the CGFZ is strongly anticorrelated to that of the southward ISOW transport along the eastern flank of the Mid‐Atlantic Ridge, suggesting an out‐of‐phase covarying transport between these two ISOW pathways.
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Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 2169-9275
ISBN Medium
Area Expedition Conference
Funding Approved $loc['no']
Call Number COAPS @ user @
Serial 952
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Author Xu, X. ; Bower, A. ; Furey, H. ; Chassignet, E.P.
Title Variability of the Iceland-Scotland Overflow Water Transport Through the Charlie-Gibbs Fracture Zone: Results From an Eddying Simulation and Observations Type $loc['typeJournal Article']
Year 2018 Publication Journal of Geophysical Research: Oceans Abbreviated Journal J. Geophys. Res. Oceans
Volume Issue 8
Pages
Keywords
Abstract Observations show that the westward transport of the Iceland‐Scotland overflow water (ISOW) through the Charlie‐Gibbs Fracture Zone (CGFZ) is highly variable. This study examines (a) where this variability comes from and (b) how it is related to the variability of ISOW transport at upstream locations in the Iceland Basin and other ISOW flow pathways. The analyses are based on a 35‐year 1/12° eddying Atlantic simulation that represents well the main features of the observed ISOW in the area of interest, in particular, the transport variability through the CGFZ. The results show that (a) the variability of the ISOW transport is closely correlated with that of the barotropic transports in the CGFZ associated with the meridional displacement of the North Atlantic Current front and is possibly induced by fluctuations of large‐scale zonal wind stress in the Western European Basin east of the CGFZ; (b) the variability of the ISOW transport is increased by a factor of 3 from the northern part of the Iceland Basin to the CGFZ region and transport time series at these two locations are not correlated, further suggesting that the variability at the CGFZ does not come from the upstream source; and (c) the variability of the ISOW transport at the CGFZ is strongly anticorrelated to that of the southward ISOW transport along the eastern flank of the Mid‐Atlantic Ridge, suggesting an out‐of‐phase covarying transport between these two ISOW pathways.
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Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 2169-9275
ISBN Medium
Area Expedition Conference
Funding Approved $loc['no']
Call Number COAPS @ user @
Serial 1023
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Author Xu, X. ; Chassignet, E.P., Wang, F.
Title On the variability of the Atlantic meridional overturning circulation transports in coupled CMIP5 simulations Type $loc['typeJournal Article']
Year 2018 Publication Climate Dynamics Abbreviated Journal Clim Dyn.
Volume 51
Issue 11
Pages 6511-6531
Keywords NAO-AMOC ; CMIP5 ; NAO index ; AMOC index ; meridional pressure gradient ; magnitude ; structure change of the NAO.
Abstract The Atlantic meridional overturning circulation (AMOC) plays a fundamental role in the climate system, and long-term climate simulations are used to understand the AMOC variability and to assess its impact. This study examines the basic characteristics of the AMOC variability in 44 CMIP5 (Phase 5 of the Coupled Model Inter-comparison Project) simulations, using the 18 atmospherically-forced CORE-II (Phase 2 of the Coordinated Ocean-ice Reference Experiment) simulations as a reference. The analysis shows that on interannual and decadal timescales, the AMOC variability in the CMIP5 exhibits a similar magnitude and meridional coherence as in the CORE-II simulations, indicating that the modeled atmospheric variability responsible for AMOC variability in the CMIP5 is in reasonable agreement with the CORE-II forcing. On multidecadal timescales, however, the AMOC variability is weaker by a factor of more than 2 and meridionally less coherent in the CMIP5 than in the CORE-II simulations. The CMIP5 simulations also exhibit a weaker long-term atmospheric variability in the North Atlantic Oscillation (NAO). However, one cannot fully attribute the weaker AMOC variability to the weaker variability in NAO because, unlike the CORE-II simulations, the CMIP5 simulations do not exhibit a robust NAO-AMOC linkage. While the variability of the wintertime heat flux and mixed layer depth in the western subpolar North Atlantic is strongly linked to the AMOC variability, the NAO variability is not.
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Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
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ISSN ISBN Medium
Area Expedition Conference
Funding Approved $loc['no']
Call Number COAPS @ rl18 @
Serial 981
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Author Xu, X. ; Chassignet, E.P. ; Firing, Y.L. ; Donohue, K.
Title Antarctic Circumpolar Current transport through Drake Passage: What can we learn from comparing high-resolution model results to observations? Type $loc['typeJournal Article']
Year 2020 Publication Journal of Geophysical Research: Oceans Abbreviated Journal J. Geophys. Res. Oceans
Volume 125
Issue 7
Pages
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Abstract Uncertainty exists in the time‐mean total transport of the Antarctic Circumpolar Current (ACC), the world�s strongest ocean current. The two most recent observational programs in Drake Passage, DRAKE and cDrake, yielded transports of 141 and 173.3 Sv, respectively. In this paper, we use a realistic 1/12° global ocean simulation to interpret these observational estimates and reconcile their differences. We first show that the modeled ACC transport in the upper 1000 m is in excellent agreement with repeat shipboard acoustic Doppler current profiler (SADCP) transects and that the exponentially decaying transport profile in the model is consistent with the profile derived from repeat hydrographic data. By further comparing the model results to the cDrake and DRAKE observations, we argue that the modeled 157.3 Sv transport, i.e. approximately the average of the cDrake and DRAKE estimates, is actually representative of the time‐mean ACC transport through the Drake Passage. The cDrake experiment overestimated the barotropic contribution in part because the array undersampled the deep recirculation southwest of the Shackleton Fracture Zone, whereas the surface geostrophic currents used in the DRAKE estimate yielded a weaker near‐surface transport than implied by the SADCP data. We also find that the modeled baroclinic and barotropic transports are not correlated, thus monitoring either baroclinic or barotropic transport alone may be insufficient to assess the temporal variability of the total ACC transport.
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Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
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ISSN ISBN Medium
Area Expedition Conference
Funding Approved $loc['no']
Call Number COAPS @ user @
Serial 1107
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Author Xu, X. ; Rhines, P.B. ; Chassignet, E.P.
Title On Mapping the Diapycnal Water Mass Transformation of the Upper North Atlantic Ocean Type $loc['typeJournal Article']
Year 2018 Publication Journal of Physical Oceanography Abbreviated Journal J. Phys. Oceanogr.
Volume 48
Issue 10
Pages 2233-2258
Keywords Atmosphere-ocean interaction ; Boundary currents ; Diapycnal mixing ; Fronts ; Thermocline circulation
Abstract Diapycnal water mass transformation is the essence behind the Atlantic meridional overturning circulation (AMOC) and the associated heat/freshwater transports. Existing studies have mostly focused on the transformation that is forced by surface buoyancy fluxes, and the role of interior mixing is much less known. This study maps the three-dimensional structure of the diapycnal transformation, both surface forced and mixing induced, using results of a high-resolution numerical model that have been shown to represent the large-scale structure of the AMOC and the North Atlantic subpolar/subtropical gyres well. The analyses show that 1) annual mean transformation takes place seamlessly from the subtropical to the subpolar North Atlantic following the surface buoyancy loss along the northward-flowing upper AMOC limb; 2) mixing, including wintertime convection and warm-season restratification by mesoscale eddies in the mixed layer and submixed layer diapycnal mixing, drives transformations of (i) Subtropical Mode Water in the southern part of the subtropical gyre and (ii) Labrador Sea Water in the Labrador Sea and on its southward path in the western Newfoundland Basin; and 3) patterns of diapycnal transformations toward lighter and denser water do not align zonally�the net three-dimensional transformation is significantly stronger than the zonally integrated, two-dimensional AMOC streamfunction (50% in the southern subtropical North Atlantic and 60% in the western subpolar North Atlantic).
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Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0022-3670
ISBN Medium
Area Expedition Conference
Funding Approved $loc['no']
Call Number COAPS @ user @
Serial 951
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Author Yin, J., E.P. Chassignet, W.G. Large, N.J. Norton, A.J. Wallcraft, and S.G. Yeager
Title Salinity boundary conditions and the Atlantic meridional overturning circulation in depth and quasi-isopycnic coordinate global ocean models Type $loc['typeJournal Article']
Year 2009 Publication Ocean Modelling Abbreviated Journal
Volume Issue Pages submitted
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Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN ISBN Medium
Area Expedition Conference
Funding Approved $loc['no']
Call Number COAPS @ mfield @
Serial 659
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Author Yu, B. ; Seed, A. ; Pu, L. ; Malone, T.
Title Integration of weather radar data into a raster GIS framework for improved flood estimation Type $loc['typeJournal Article']
Year 2019 Publication Atmospheric Science Letters Abbreviated Journal Atmos. Sci. Lett.
Volume 6
Issue 1
Pages
Keywords
Abstract We present in this paper the interannual variability of seasonal temperature and rainfall in the Indian meteorological subdivisions (IMS) for boreal winter and summer seasons that take in to account the varying length of the seasons.Our study reveals that accounting for the variations in the length of the sea-sons produces stronger teleconnections between the seasonal anomalies of surface temperature and rainfall over India with corresponding sea surface temperature anomalies of the tropical Oceans (especially over the northern Indian and the equatorial Pacific Oceans) compared to the same teleconnections from fixed length seasons over the IMS. It should be noted that the IMS show significant spatial heterogeneity in these teleconnections
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Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 1530-261X
ISBN Medium
Area Expedition Conference
Funding Approved $loc['no']
Call Number COAPS @ user @
Serial 1069
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Author Yu, P
Title Development of New Techniques for Assimilating Satellite Altimetry Data into Ocean Models Type $loc['typeManuscript']
Year 2006 Publication Abbreviated Journal
Volume Issue Pages
Keywords Data Assimilation, Reduced Space, First Baroclinic Mode, Ocean Models, Vertical Normal Mode Decomposition, Variational
Abstract State of the art fully three-dimensional ocean models are very computationally expensive and their adjoints are even more resource intensive. However, many features of interest are approximated by the first baroclinic mode over much of the ocean, especially in the lower and mid latitude regions. Based on this dynamical feature, a new type of data assimilation scheme to assimilate sea surface height (SSH) data, a reduced-space adjoint technique, is developed and implemented with a three-dimensional model using vertical normal mode decomposition. The technique is tested with the Navy Coastal Ocean Model (NCOM) configured to simulate the Gulf of Mexico. The assimilation procedure works by minimizing the cost function, which generalizes the misfit between the observations and their counterpart model variables. The “forward” model is integrated for the period during which the data are assimilated. Vertical normal mode decomposition retrieves the first baroclinic mode, and the data misfit between the model outputs and observations is calculated. Adjoint equations based on a one-active-layer reduced gravity model, which approximates the first baroclinic mode, are integrated backward in time to get the gradient of the cost function with respect to the control variables (velocity and SSH of the first baroclinic mode). The gradient is input to an optimization algorithm (the limited memory Broyden-Fletcher-Goldfarb-Shanno (BFGS) method is used for the cases presented here) to determine the new first baroclinic mode velocity and SSH fields, which are used to update the forward model variables at the initial time. Two main issues in the area of ocean data assimilation are addressed: 1. How can information provided only at the sea surface be transferred dynamically into deep layers? 2. How can information provided only locally, in limited oceanic regions, be horizontally transferred to ocean areas far away from the data-dense regions, but dynamically connected to it? The first problem is solved by the use of vertical normal mode decomposition, through which the vertical dependence of model variables is obtained. Analyses show that the first baroclinic mode SSH represents the full SSH field very closely in the model test domain, with a correlation of 93% in one of the experiments. One common way to solve the second issue is to lengthen the assimilation window in order to allow the dynamic model to propagate information to the data-sparse regions. However, this dramatically increases the computational cost, since many oceanic features move very slowly. An alternative solution to this is developed using a mapping method based on complex empirical orthogonal functions (EOF), which utilizes data from a much longer period than the assimilation cycle and deals with the information in space and time simultaneously. This method is applied to map satellite altimeter data from the ground track observation locations and times onto a regular spatial and temporal grid. Three different experiments are designed for testing the assimilation technique: two experiments assimilate SSH data produced from a model run to evaluate the method, and in the last experiment the technique is applied to TOPEX/Poseidon and Jason-1 altimeter data. The assimilation procedure converges in all experiments and reduces the error in the model fields. Since the adjoint, or “backward”, model is two-dimensional, the method is much more computationally efficient than if it were to use a fully three-dimensional backward model.
Address Department of Oceanography
Corporate Author Thesis $loc['Ph.D. thesis']
Publisher Florida State University
Place of Publication Tallahassee, FL
Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN ISBN Medium
Area Expedition Conference
Funding NSF, ONR, NASA
Approved $loc['no']
Call Number COAPS @ mfield @
Serial 589
Permanent link to this record
