Rypina
Irina I.
Rypina
Irina I.
No Thumbnail Available
Search Results
Now showing
1  4 of 4

ArticleObserving and quantifying ocean flow properties using drifters with drogues at different depths(American Meteorological Society, 20210716) Rypina, Irina I. ; Getscher, Timothy ; Pratt, Lawrence J. ; Mourre, BaptisteThis paper presents analyses of drifters with drogues at different depths—1, 10, 30, and 50 m—that were deployed in the Mediterranean Sea to investigate frontal subduction and upwelling. Drifter trajectories were used to estimate divergence, vorticity, vertical velocity, and finitesize Lyapunov exponents (FTLEs) and to investigate the balance of terms in the vorticity equation. The divergence and vorticity are O(f) and change sign along trajectories. Vertical velocity is O(1 mm s−1), increases with depth, indicates predominant upwelling with isolated downwelling events, and sometimes changes sign between 1 and 50 m. Vortex stretching is one of the significant terms, but not the only one, in the vorticity balance. Twodimensional FTLEs are 2 × 10−5 s−1 after 1 day, 2 times as large as in a 400mresolution numerical model. Threedimensional FTLEs are 50% larger than 2D FTLEs and are dominated by the vertical shear of horizontal velocity. Bootstrapping suggests uncertainty levels of ~10% of the timemean absolute values for divergence and vorticity. Analysis of simulated drifters in a model suggests that drifterbased estimates of divergence and vorticity are close to the Eulerian model estimates, except when drifters get aligned into long filaments. Drifterbased vertical velocity is close to the Eulerian model estimates at 1 m but differs at deeper depths. The errors in the vertical velocity are largely due to the lateral separation between drifters at different depths and are partially due to only measuring at four depths. Overall, this paper demonstrates how drifters, heretofore restricted to 2D nearsurface observations, can be used to learn about 3D flow properties throughout the upper layer of the water column.

ArticleEddyinduced particle dispersion in the nearsurface North Atlantic(American Meteorological Society, 201212) Rypina, Irina I. ; Kamenkovich, Igor V. ; Berloff, Pavel S. ; Pratt, Lawrence J.This study investigates the anisotropic properties of the eddyinduced material transport in the nearsurface North Atlantic from two independent datasets, one simulated from the sea surface height altimetry and one derived from realocean surface drifters, and systematically examines the interactions between the mean and eddyinduced material transport in the region. The Lagrangian particle dispersion, which is widely used to characterize the eddyinduced tracer fluxes, is quantified by constructing the “spreading ellipses.” The analysis consistently demonstrates that this dispersion is spatially inhomogeneous and strongly anisotropic. The spreading is larger and more anisotropic in the subtropical than in the subpolar gyre, and the largest ellipses occur in the Gulf Stream vicinity. Even at times longer than half a year, the spreading exhibits significant nondiffusive behavior in some parts of the domain. The eddies in this study are defined as deviations from the longterm timemean. The contributions from the climatological annual cycle, interannual, and subannual (shorter than one year) variability are investigated, and the latter is shown to have the strongest effect on the anisotropy of particle spreading. The influence of the mean advection on the eddyinduced particle spreading is investigated using the “eddyfollowingfulltrajectories” technique and is found to be significant. The role of the Ekman advection is, however, secondary. The pronounced anisotropy of particle dispersion is expected to have important implications for distributing oceanic tracers, and for parameterizing eddyinduced tracer transfer in noneddyresolving models.

ArticleEulerian and Lagrangian correspondence of highfrequency radar and surface drifter data : effects of radar resolution and flow components(American Meteorological Society, 201404) Rypina, Irina I. ; Kirincich, Anthony R. ; Limeburner, Richard ; Udovydchenkov, Ilya A.This study investigated the correspondence between the nearsurface drifters from a mass drifter deployment near Martha’s Vineyard, Massachusetts, and the surface current observations from a network of three highresolution, highfrequency radars to understand the effects of the radar temporal and spatial resolution on the resulting Eulerian current velocities and Lagrangian trajectories and their predictability. The radarbased surface currents were found to be unbiased in direction but biased in magnitude with respect to drifter velocities. The radar systematically underestimated velocities by approximately 2 cm s−1 due to the smoothing effects of spatial and temporal averaging. The radar accuracy, quantified by the domainaveraged rms difference between instantaneous radar and drifter velocities, was found to be about 3.8 cm s−1. A Lagrangian comparison between the real and simulated drifters resulted in the separation distances of roughly 1 km over the course of 10 h, or an equivalent separation speed of approximately 2.8 cm s−1. The effects of the temporal and spatial radar resolution were examined by degrading the radar fields to coarser resolutions, revealing the existence of critical scales (1.5–2 km and 3 h) beyond which the ability of the radar to reproduce drifter trajectories decreased more rapidly. Finally, the importance of the different flow components present during the experiment—mean, tidal, locally winddriven currents, and the residual velocities—was analyzed, finding that, during the study period, a combination of tidal, locally winddriven, and mean currents were insufficient to reliably reproduce, with minimal degradation, the trajectories of real drifters. Instead, a minimum combination of the tidal and residual currents was required.

ArticleMultiiteration approach to studying tracer spreading using drifter data(American Meteorological Society, 20170131) Rypina, Irina I. ; Fertitta, David ; Macdonald, Alison M. ; Yoshida, Sachiko ; Jayne, Steven R.A novel multiiteration statistical method for studying tracer spreading using drifter data is introduced. The approach allows for the best use of the available drifter data by making use of a simple iterative procedure, which results in the statistically probable map showing the likelihood that a tracer released at some source location would visit different geographical regions, along with the associated arrival travel times. The technique is tested using real drifter data in the North Atlantic. Two examples are considered corresponding to sources in the western and eastern North Atlantic Ocean, that is, Massachusetts Bay–like and Irish Sea–like sources, respectively. In both examples, the method worked well in estimating the statistics of the tracer transport pathways and travel times throughout the entire North Atlantic. The role of eddies versus mean flow is quantified using the same technique, and eddies are shown to significantly broaden the spread of a tracer. The sensitivity of the results to the size of the source domain is investigated and causes for this sensitivity are discussed.