scholarly journals Potential Artifacts of Sequential State Estimation Invariants

2021 ◽  
Author(s):  
Carl Wunsch
Keyword(s):  
Initial Conditions ◽  
Current System ◽  
Sequential Estimation ◽  
Estimation Methods ◽  
Western Boundary ◽  
State Variables ◽  
Random Errors ◽  
Boundary Current ◽  
Mass Spring ◽  
General Climate

Abstract. In sequential estimation methods often used in general climate or oceanic calculations of the state and of forecasts, observations act mathematically and statistically as forcings as is obvious in the innovation form of the equations. For purposes of calculating changes in important functions of state variables such as total mass and energy, or in volumetric current transports, results are sensitive to mis-representation of a large variety of parameters including initial conditions, prior uncertainty covariances, and systematic and random errors in observations. Errors are both stochastic and systematic, with the latter, as usual, being the most intractable. Here some of the consequences of such errors are first analyzed in the context of a simplified mass-spring oscillator system exhibiting many of the issues of far more complicated realistic problems. The same methods are then applied to a more geophysical barotropic Rossby wave plus western boundary current system. The overall message is that convincing trend and other time-dependent determinations in "reanalyis" like estimates requires a full understanding of both models and observations.

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

2019 ◽  
Vol 12 (7) ◽  
pp. 3329-3355 ◽  
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.

scholarly journals Weak Thermocline Mixing in the North Pacific Low-Latitude Western Boundary Current System

2017 ◽  
Vol 44 (20) ◽  
pp. 10,530-10,539 ◽  
Author(s):  
Zhiyu Liu ◽  
Qiang Lian ◽  
Fangtao Zhang ◽  
Lei Wang ◽  
Mingming Li ◽  
...  
Keyword(s):  
North Pacific ◽  
Current System ◽  
Western Boundary Current ◽  
Western Boundary ◽  
Boundary Current ◽  
Low Latitude ◽  
The North ◽  
The North Pacific

Directional Extreme Current Profiles Based on Complex Empirical Orthogonal Functions (C-EOF) for Offshore Design

2009 ◽  
Author(s):  
Jose Antonio Moreira Lima ◽  
Eric Oliveira Ribeiro ◽  
Wellington Ceccopieri ◽  
Guisela Grossmann Matheson
Keyword(s):  
Goodness Of Fit ◽  
Structural Reliability ◽  
Current System ◽  
Correlation Coefficients ◽  
Current Data ◽  
Empirical Orthogonal Functions ◽  
Western Boundary ◽  
Boundary Current ◽  
Orthogonal Functions ◽  
Brazil Current

This paper presents a methodology to estimate deep water design current profiles using Complex Empirical Orthogonal Function (C-EOF) and a structural reliability response based model. The advantage of C-EOF is the capability of directly obtaining directional extreme current profiles. It is estimated that most of the variability of the southeast Brazil current system can be explained by the first two EOF modes. The first mode associated with the southwestward Brazil Current (BC) and the second mode with the northeastward Intermediate Western Boundary Current (IWBC). Thus, only two series of C-EOF amplitudes can be used in the response based technique to estimate the 100-y extreme current values. The methodology can also be used with more EOF modes if required to properly represent the current data. The probabilistic cumulative functions are based on extreme value distributions such as Gumbel or Weibull, and Lognormal for conditional distributions. The evaluation of estimated distribution parameters are carried out using Kolmogorov-Smirnov goodness-of-fit hypothesis tests and correlation coefficients for each directional sector.

scholarly journals Mean Conditions and Seasonality of the West Greenland Boundary Current System near Cape Farewell

2020 ◽  
Vol 50 (10) ◽  
pp. 2849-2871
Author(s):  
Astrid Pacini ◽  
Robert S. Pickart ◽  
Frank Bahr ◽  
Daniel J. Torres ◽  
Andrée L. Ramsey ◽  
...  
Keyword(s):  
Current System ◽  
Labrador Sea ◽  
Western Boundary ◽  
Coastal Current ◽  
Boundary Current ◽  
The West ◽  
West Greenland ◽  
Irminger Sea ◽  
West Greenland Current ◽  
Recirculation Gyre

AbstractThe structure, transport, and seasonal variability of the West Greenland boundary current system near Cape Farewell are investigated using a high-resolution mooring array deployed from 2014 to 2018. The boundary current system is comprised of three components: the West Greenland Coastal Current, which advects cold and fresh Upper Polar Water (UPW); the West Greenland Current, which transports warm and salty Irminger Water (IW) along the upper slope and UPW at the surface; and the Deep Western Boundary Current, which advects dense overflow waters. Labrador Sea Water (LSW) is prevalent at the seaward side of the array within an offshore recirculation gyre and at the base of the West Greenland Current. The 4-yr mean transport of the full boundary current system is 31.1 ± 7.4 Sv (1 Sv ≡ 106 m3 s−1), with no clear seasonal signal. However, the individual water mass components exhibit seasonal cycles in hydrographic properties and transport. LSW penetrates the boundary current locally, through entrainment/mixing from the adjacent recirculation gyre, and also enters the current upstream in the Irminger Sea. IW is modified through air–sea interaction during winter along the length of its trajectory around the Irminger Sea, which converts some of the water to LSW. This, together with the seasonal increase in LSW entering the current, results in an anticorrelation in transport between these two water masses. The seasonality in UPW transport can be explained by remote wind forcing and subsequent adjustment via coastal trapped waves. Our results provide the first quantitatively robust observational description of the boundary current in the eastern Labrador Sea.

A two-layer approximation to the Brazil Current–Intermediate Western Boundary Current System between 20°S and 28°S

2009 ◽  
Vol 29 (2) ◽  
pp. 154-158 ◽  
Author(s):  
Alexandre M. Fernandes ◽  
Ilson C.A. da Silveira ◽  
Leandro Calado ◽  
Edmo J.D. Campos ◽  
Afonso M. Paiva
Keyword(s):  
Current System ◽  
Western Boundary Current ◽  
Western Boundary ◽  
Boundary Current ◽  
Brazil Current

scholarly journals FIFTY YEARS AGO YU. A. IVANOV WITH HIS COLLEAGUES DISCOVERED THE ANTILLES-GUIANA CURRENT

2019 ◽  
Vol 47 (2) ◽  
pp. 64-75
Author(s):  
V.G. Neiman
Keyword(s):  
Large Scale ◽  
Current System ◽  
Western Boundary ◽  
Boundary Current ◽  
Shirshov Institute ◽  
Actual System ◽  
Direct Measurements ◽  
History Of ◽  
Academy Of Sciences ◽  
First Time

A brief history of the Antilles-Guiana Current discovery during cruise 5 of the scientific research vessel (R/V) “Akademik Kurchatov” in 1969 in the Atlantic Ocean is presented. This expedition of the Shirshov Institute of Oceanology of the USSR Academy of Sciences was targeted for experimental study of the Western Boundary Current System in the tropical Atlantic. The previous studies in this region revealed signs of the Southern flow within the system, which overall meridional velocity component was of the Northern direction. However, the traces of Southern currents in all such cases were usually interpreted as a manifestation of a large-scale eddy activity in the velocity field of the main North-Western water transport. In the expedition of 1969, for the first time in the Russian oceanography a non-trivial method for the direct measurements of a current velocity was applied. It is based on the results of an immediate preliminary hydrographic survey of the area, which proposed by Y.A. Ivanov. This method has made possible to determine in details the actual system of the Western boundary flows, in which the previously unknown to science the Antilles-Guiana Current was discovered. The other Russian expeditions, which have been carried out in 1970 and 1972 during 9 and 12 cruises of the R/V “Akademik Kurchatov”, revealed the interannual stability of this flow, including the mass transport, approximately equal to 30 Sv, i.e. almost half of the volume of water carried by the Gulf Stream.

A NUMERICAL STUDY OF THE BRAZILIAN SHELF/SLOPE REGION SOUTH OF 13S USING THE OCEAN MODEL ROMS

2014 ◽  
Vol 31 (2) ◽  
Author(s):  
Janini Pereira ◽  
Mauro Cirano ◽  
Martinho Marta-almeida ◽  
Fabiola Negreiros Amorim
Keyword(s):  
Numerical Study ◽  
Current System ◽  
Mixed Layer Depth ◽  
Ocean Model ◽  
Western Boundary ◽  
Boundary Current ◽  
Data Set ◽  
Regional Ocean Model System ◽  
Brazil Current ◽  
Shelf Slope

The oceanic features in the eastern and southeastern brazilian shelf/slope south of 13S is investigated using ROMS (Regional Ocean Model System). The model integration was 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 well the BC (Brazil Current)-IWBC (IntermediateWestern Boundary Current) System. The BC - IWBC system at 22S cross-shelf section, where the mean alongshelf velocity represents our simulation capability of reproducing the western boundary currents, 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.

Sign in / Sign up

Export Citation Format

Share Document