Search Results

You are looking at 1 - 10 of 11 items for

  • Author or Editor: Philip L. Richardson x
  • Refine by Access: All Content x
Clear All Modify Search
Philip L. Richardson

Abstract

During the period 1976–78, the movement of 14 Gulf Stream rings, including two anticyclonic and 12 cyclonic rings, was measured with satellite-tracked free-drifting buoys. The buoys in the cyclonic rings showed a tendency to move out toward the high-velocity region of the ring and to remain there circling the center. One buoy stayed in a ring as long as 8 months and completed 86 loops. Periods of rotation ranged from less than 2 days up to 10 days. The movement of the rings was complicated and appears to be related to the Gulf Stream and strong topographic features such as the New England Seamounts. Rings that were not touching the Stream generally moved westward with typical speeds of 5 cm s−1. Rings that were attached to the Stream generally moved downstream in the Stream with speeds up to 75 cm s−1. Frequently rings coalesced with the Gulf Stream and one of the following three things seemed to happen: 1) the ring turned into an open meander of the Stream and was lost; 2) the ring was advected rapidly downstream in the Stream and was presumably lost; and 3) the ring became attached to the Gulf Stream and then split off again as a modified ring. The results of this study, that frequently strong interactions occur between rings and the Gulf Stream, are in contrast to my original view that rings slowly translate southwestward through the Sargasso Sea and gradually decay there.

Full access
Philip L. Richardson and Kenneth Mooney

Abstract

The influence of the subtropical gyre on the spread of Mediterranean Water in the Atlantic is discussed in terms of a simple horizontal advection-diffusion model. The northern, southern and western boundaries of a rectangular ocean are treated as salt sinks while the distribution of salinity on the east coast representing the highly saline Mediterranean Water is a sine curve. The velocity distribution for the subtropical gyre is that given by Stommel and includes westward intensification. Salinity distributions are calculated for various values of the Peclet number, and for oceanographically reasonable values they indicate that the gyre passes through the high-salinity tongue and advects it toward the south and west. The model is consistent with the observed salinity distribution of the mid-layers of the North Atlantic.

Full access
David Walsh, Philip L. Richardson, and Jim Lynch

Abstract

SOFAR floats at different depths within two Mediterranean Water eddies (meddies) reveal that the meddy rotation axes tilt transversely with respect to the meddy translation direction. The rotation axis of one of the meddies (Meddy 1) was displaced by about 6 km over a depth of roughly 100 m; the axis of the second meddy (Meddy 2) was displaced by about 0.4 km over 100-m depth. These results are compared to a simple theoretical model that predicts the deformation and translation of a lens-shaped eddy embedded in large-scale external shear. Observed lateral deformations of the meddles are in good agreement with model predictions. The observed tilt of Meddy 1 is attributed to a combination of depth-varying rotation rate beneath the meddy core and the horizontal translation of the meddy; the tilt of Meddy 2 is attributed to a deformation of the meddy core by vertically sheared flow outside the meddy. The observed translation speed of the meddies with respect to nearby floats outside of the meddies is significantly larger than that predicted by the model.

Full access
David M. Fratantoni and Philip L. Richardson

Abstract

Two neutrally buoyant SOFAR floats vigorously looped and meandered at depths of 950–1150 m in the eastern tropical Atlantic Ocean. The float trajectories illustrate a poleward flow along the tropical eastern boundary and significant intermediate-depth mesoscale variability in the low-latitude eastern basin. One float, caught within an energetic cyclonic eddy near the eastern boundary, looped cyclonically 14 times while translating 600 km northward parallel to the African coastline. A second float, launched near the Mid-Atlantic Ridge, meandered eastward with a Lagrangian zonal wavelength of 400 km and meridional amplitude exceeding 200 km. Satellite infrared imagery indicates that horizontal shear associated with the system of near-surface zonal equatorial currents may contribute to the observed intermediate-depth variability.

Full access
David M. Fratantoni and Philip L. Richardson

Abstract

Subsurface float and surface drifter observations illustrate the structure, evolution, and eventual demise of 10 North Brazil Current (NBC) rings as they approached and collided with the Lesser Antilles in the western tropical Atlantic Ocean. Upon encountering the shoaling topography east of the Lesser Antilles, most of the rings were deflected abruptly northward and several were observed to completely engulf the island of Barbados. The near-surface and subthermocline layers of two rings were observed to cleave or separate upon encountering shoaling bathymetry between Tobago and Barbados, with the resulting portions each retaining an independent and coherent ringlike vortical circulation. Surface drifters and shallow (250 m) subsurface floats that looped within NBC rings were more likely to enter the Caribbean through the passages of the Lesser Antilles than were deeper (500 or 900 m) floats, indicating that the regional bathymetry preferentially inhibits transport of intermediate-depth ring components. No evidence was found for the wholesale passage of rings through the island chain.

Full access
David Y. Lai and Philip L. Richardson

Abstract

The distribution, number and movement of cyclonic Gulf Stream rings were estimated from an analysis of 50 000 temperature records obtained from the National Oceanographic Data Center and Fleet Numerical Weather Central. The data were taken from 1970 through September 1976 in the region bounded by 20–40°N and 50–80°W. Additional ring observations from other sources were also used. Twenty-five ring time series, together with 26 single ring observations were obtained; approximately 11 rings were found to exist at one time. Rings typically moved westward, turned southwest when close to the Gulf Stream and appeared to coalesce with the Stream near Florida. On the average, two rings per year moved down this path with a mean speed of 3 km day−1 and an estimated life span of 2–3 years. Although ring observations were concentrated in the northwestern Sargasso Sea, several were documented east of 60°W. In addition to cold core rings several warm eddies were found south of the Stream; they consisted of at least a 150 m deepening of the main thermocline. The movement of anticyclonic rings north of the Stream was also determined; approximately three exist at a single time and they move westward with a mean speed of 5 km day−1.

Full access
Laurence Armi, Dave Hebert, Neil Oakey, James F. Price, Philip L. Richardson, H. Thomas Rossby, and Barry Ruddick

Abstract

A lens of Mediterranean water (Meddy) was tracked in the eastern North Atlantic for two years with SOFAR floats. The Meddy was first found between the Canary Islands and the Azores in October 1984. It center moved in an irregular pattern, at speeds of a few cm s−1, and translated 1100 km to the south in two years. This Meddy was surveyed four times by CTD and velocity profilers, and once with the microstructure profiler EPSONDE. When observed during the first two surveys the Meddy had a core that was stably and smoothly stratified in both salinity and temperature, nearly uniform in the horizontal, and was saltier than the surrounding ocean by 0.65 psu. The Meddy was eroded from its edges, top and bottom, and lost salt and hat with an e-folding time of about one year. The salinity at the center remained at its original value during the first year and decreased during the second year. Evidence was seen for mixing by lateral intrusions, double diffusion, and turbulence; the intrusions are thought to be the most important mode of mixing in terms of salt and heat loss.

Radial profiles of azimuthal velocity revealed a core in almost solid body rotation, with a period of 5–6 days corresponding to 0.35 times the local Coriolis parameter. During the October 1984 survey, the azimuthal speed had a maximum of 0.3 m s−1 at a radius of 24 km. Both the radius and magnitude of the velocity maximum decreased with time. The anticyclonic circulation attained a maximum at the radius of the salinity front. As the lens was eroded from the sides, the radius of maximum velocity and the maximum velocity both decreased, but the rotation rate of the core remained fairly steady.

Full access
Thomas Lauvaux, Natasha L. Miles, Scott J. Richardson, Aijun Deng, David R. Stauffer, Kenneth J. Davis, Gloria Jacobson, Chris Rella, Gian-Paul Calonder, and Philip L. DeCola

Abstract

Anthropogenic emissions from urban areas represent 70% of the fossil fuel carbon emitted globally according to carbon emission inventories. The authors present here the first operational system able to monitor in near–real time daily emission estimates, using a mesoscale atmospheric inversion framework over the city of Davos, Switzerland, before, during, and after the World Economic Forum 2012 Meeting (WEF-2012). Two instruments that continuously measured atmospheric mixing ratios of greenhouse gases (GHGs) were deployed at two locations from 23 December 2011 to 3 March 2012: one site was located in the urban area and the other was out of the valley in the surrounding mountains. Carbon dioxide, methane, and carbon monoxide were measured continuously at both sites. The Weather Research and Forecasting mesoscale atmospheric model (WRF), in four-dimensional data assimilation mode, was used to simulate the transport of GHGs over the valley of Davos at 1.3-km resolution. Wintertime emissions prior to the WEF-2012 were about 40% higher than the initial annual inventory estimate, corresponding to the use of heating fuel in the winter. Daily inverse fluxes were highly correlated with the local climate, especially during the severe cold wave that affected most of Europe in early February 2012. During the WEF-2012, emissions dropped by 35% relative to the first month of the deployment, despite similar temperatures and the presence of several thousand participants at the meeting. On the basis of composite diurnal cycles of hourly CO/CO2 ratios, the absence of traffic peaks during the WEF-2012 meeting indicated that change in road emissions is potentially responsible for the observed decrease in the city emissions during the meeting.

Full access
William J. Schmitz, Jr., James F. Price, Philip L. Richardson, W. Brechner Owens, Douglas C. Webb, Robert E. Cheney, and H. Thomas Rossby

Abstract

SOFAR (sound fixing and ranging) floats deployed for engineering tests during 1977–79 yield the first long-term quasi-Lagrangian observations in the subsurface Gulf Stream System. The character of these float tracks supports the premise that the Gulf Stream is a persistent, large-scale, vertically coherent jet at depths (approximately) within and above the main thermocline. where mean and eddy kinetic energies are roughly the same and lateral motions of the Stream are clearly delineated. A float track at thermocline depth is visually coherent with the track of a concurrently launched surface drifter over the larger horizontal scales traversed during the first few months of their trajectories. Below thermocline depths, fluctuation or eddy kinetic energies are normally larger than the mean and a persistent Gulf Stream is difficult to detect. However, deep motions that are visually coherent with upper level flows may be observed for an intermediate range of space and time scales.

Eddy kinetic energies based on the float data are compatible with existing Eulerian estimates to the extent comparable. The consistency of a quasi-Lagrangian eddy kinetic energy estimate in the vicinity of the thermocline, roughly 400 cm2 s−2, the first such observation to our knowledge, is indirect but relatively convincing. Zonal and meridional variances for the float data are also in line with existing Eulerian results. Estimates of the frequency distribution of eddy kinetic energy for the longest float trajectory available are nearly identical to comparable Eulerian results at frequencies less than about a cycle per 20 days.

Full access
Robert J. H. Dunn, F. Aldred, Nadine Gobron, John B. Miller, Kate M. Willett, M. Ades, Robert Adler, Richard, P. Allan, Rob Allan, J. Anderson, Anthony Argüez, C. Arosio, John A. Augustine, C. Azorin-Molina, J. Barichivich, H. E. Beck, Andreas Becker, Nicolas Bellouin, Angela Benedetti, David I. Berry, Stephen Blenkinsop, Olivier Bock, X. Bodin, Michael G. Bosilovich, Olivier Boucher, S. A. Buehler, B. Calmettes, Laura Carrea, Laura Castia, Hanne H. Christiansen, John R. Christy, E.-S. Chung, Melanie Coldewey-Egbers, Owen R. Cooper, Richard C. Cornes, Curt Covey, J.-F. Cretaux, M. Crotwell, Sean M. Davis, Richard A. M. de Jeu, Doug Degenstein, R. Delaloye, Larry Di Girolamo, Markus G. Donat, Wouter A. Dorigo, Imke Durre, Geoff S. Dutton, Gregory Duveiller, James W. Elkins, Vitali E. Fioletov, Johannes Flemming, Michael J. Foster, Stacey M. Frith, Lucien Froidevaux, J. Garforth, Matthew Gentry, S. K. Gupta, S. Hahn, Leopold Haimberger, Brad D. Hall, Ian Harris, D. L. Hemming, M. Hirschi, Shu-pen (Ben) Ho, F. Hrbacek, Daan Hubert, Dale F. Hurst, Antje Inness, K. Isaksen, Viju O. John, Philip D. Jones, Robert Junod, J. W. Kaiser, V. Kaufmann, A. Kellerer-Pirklbauer, Elizabeth C. Kent, R. Kidd, Hyungjun Kim, Z. Kipling, A. Koppa, B. M. Kraemer, D. P. Kratz, Xin Lan, Kathleen O. Lantz, D. Lavers, Norman G. Loeb, Diego Loyola, R. Madelon, Michael Mayer, M. F. McCabe, Tim R. McVicar, Carl A. Mears, Christopher J. Merchant, Diego G. Miralles, L. Moesinger, Stephen A. Montzka, Colin Morice, L. Mösinger, Jens Mühle, Julien P. Nicolas, Jeannette Noetzli, Ben Noll, J. O’Keefe, Tim J. Osborn, T. Park, A. J. Pasik, C. Pellet, Maury S. Pelto, S. E. Perkins-Kirkpatrick, G. Petron, Coda Phillips, S. Po-Chedley, L. Polvani, W. Preimesberger, D. G. Rains, W. J. Randel, Nick A. Rayner, Samuel Rémy, L. Ricciardulli, A. D. Richardson, David A. Robinson, Matthew Rodell, N. J. Rodríguez-Fernández, K.H. Rosenlof, C. Roth, A. Rozanov, T. Rutishäuser, Ahira Sánchez-Lugo, P. Sawaengphokhai, T. Scanlon, Verena Schenzinger, R. W. Schlegel, S. Sharma, Lei Shi, Adrian J. Simmons, Carolina Siso, Sharon L. Smith, B. J. Soden, Viktoria Sofieva, T. H. Sparks, Paul W. Stackhouse Jr., Wolfgang Steinbrecht, Martin Stengel, Dimitri A. Streletskiy, Sunny Sun-Mack, P. Tans, S. J. Thackeray, E. Thibert, D. Tokuda, Kleareti Tourpali, Mari R. Tye, Ronald van der A, Robin van der Schalie, Gerard van der Schrier, M. van der Vliet, Guido R. van der Werf, A. Vance, Jean-Paul Vernier, Isaac J. Vimont, Holger Vömel, Russell S. Vose, Ray Wang, Markus Weber, David Wiese, Anne C. Wilber, Jeanette D. Wild, Takmeng Wong, R. Iestyn Woolway, Xinjia Zhou, Xungang Yin, Guangyu Zhao, Lin Zhao, Jerry R. Ziemke, Markus Ziese, and R. M. Zotta
Full access