ORCID Profile
0000-0003-2325-5340
Current Organisations
Colorado State University
,
University of Reading
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Publications
A weaker Agulhas Current leads to more Agulhas leakage
Publisher: American Geophysical Union (AGU)
Date: 02-2009
DOI: 10.1029/2008GL036614
Fast Northward Energy Transfer in the Atlantic due to Agulhas Rings
Publisher: American Meteorological Society
Date: 09-2007
DOI: 10.1175/JPO3108.1
Abstract: The adiabatic transit time of wave energy radiated by an Agulhas ring released in the South Atlantic Ocean to the North Atlantic Ocean is investigated in a two-layer ocean model. Of particular interest is the arrival time of baroclinic energy in the northern part of the Atlantic, because it is related to variations in the meridional overturning circulation. The influence of the Mid-Atlantic Ridge is also studied, because it allows for the conversion from barotropic to baroclinic wave energy and the generation of topographic waves. Barotropic energy from the ring is present in the northern part of the model basin within 10 days. From that time, the barotropic energy keeps rising to attain a maximum 500 days after initiation. This is independent of the presence or absence of a ridge in the model basin. Without a ridge in the model, the travel time of the baroclinic signal is 1300 days. This time is similar to the transit time of the ring from the eastern to the western coast of the model basin. In the presence of the ridge, the baroclinic signal arrives in the northern part of the model basin after approximately 10 days, which is the same time scale as that of the barotropic signal. It is apparent that the ridge can facilitate the energy conversion from barotropic to baroclinic waves and the slow baroclinic adjustment can be bypassed. The meridional overturning circulation, parameterized in two ways as either a purely barotropic or a purely baroclinic phenomenon, also responds after 1300 days. The ring temporarily increases the overturning strength. The presence of the ridge does not alter the time scales.
SEASTAR: A Mission to Study Ocean Submesoscale Dynamics and Small-Scale Atmosphere-Ocean Processes in Coastal, Shelf and Polar Seas
Publisher: Frontiers Media SA
Date: 13-08-2019
Lagrangian validation of numerical drifter trajectories using drifting buoys: Application to the Agulhas system
Publisher: Elsevier BV
Date: 2009
On the fast decay of Agulhas rings
Publisher: American Geophysical Union (AGU)
Date: 06-03-2010
DOI: 10.1029/2009JC005585
Multiplicative Non‐Gaussian Model Error Estimation in Data Assimilation
Publisher: American Geophysical Union (AGU)
Date: 04-2022
DOI: 10.1029/2021MS002564
Abstract: Model uncertainty quantification is an essential component of effective data assimilation. Model errors associated with sub‐grid scale processes are often represented through stochastic parameterizations of the unresolved process. Many existing Stochastic Parameterization schemes are only applicable when knowledge of the true sub‐grid scale process or full observations of the coarse scale process are available, which is typically not the case in real applications. We present a methodology for estimating the statistics of sub‐grid scale processes for the more realistic case that only partial observations of the coarse scale process are available. Model error realizations are estimated over a training period by minimizing their conditional sum of squared deviations given some informative covariates (e.g., state of the system), constrained by available observations and assuming that the observation errors are smaller than the model errors. From these realizations a conditional probability distribution of additive model errors given these covariates is obtained, allowing for complex non‐Gaussian error structures. Random draws from this density are then used in actual ensemble data assimilation experiments. We demonstrate the efficacy of the approach through numerical experiments with the multi‐scale Lorenz 96 system using both small and large time scale separations between slow (coarse scale) and fast (fine scale) variables. The resulting error estimates and forecasts obtained with this new method are superior to those from two existing methods.
Flux comparison of Eulerian and Lagrangian estimates of Agulhas leakage: A case study using a numerical model
Publisher: Elsevier BV
Date: 03-2010
Related Organisations
University Of Reading
Location: United Kingdom of Great Britain and Northern Ireland
Related Funding Activities
No related grants have been discovered for Peter Jan van Leeuwen.