Physical Oceanography (PO)
http://hdl.handle.net/1912/7
2016-04-29T15:58:58Z
2016-04-29T15:58:58Z
Dynamic presentation of Long Term Upper Ocean Study (LOTUS) data using videotape
Montgomery, Ellyn T.
http://hdl.handle.net/1912/7957
2016-04-22T13:06:39Z
1986-09-01T00:00:00Z
Dynamic presentation of Long Term Upper Ocean Study (LOTUS) data using videotape
Montgomery, Ellyn T.
In order to show efficiently the large amount of data obtained during
the Long Term Upper Ocean Study (LOTUS), a new method of data presentation
was developed. Three data variables can be included in a simple color contour
plot, but if successive color contour plots are recorded on videotape,
a fourth variable, time, can also be shown.
This report documents the process of making a videotape presenting
scientific data in this way, from raw data to finished videotape. The videotape
shows internal wave kinetic energy versus frequency and depth; the
time variation of the videotape displays real time variation in the ratio
of 14/30 second to one week, or about l month of data every 2 seconds.
1986-09-01T00:00:00Z
SOFAR float Mediterranean outflow experiment data from the first year, 1984-1985
Price, James F.
McKee, Theresa K.
Valdes, James R.
Richardson, Philip L.
Armi, Laurence
http://hdl.handle.net/1912/7956
2016-04-22T08:02:43Z
1986-07-01T00:00:00Z
SOFAR float Mediterranean outflow experiment data from the first year, 1984-1985
Price, James F.; McKee, Theresa K.; Valdes, James R.; Richardson, Philip L.; Armi, Laurence
In October, 1984, the Woods Hole Oceanographic Institution SOFAR float
group began a three-year long field program to observe the low frequency
currents in the Canary Basin. The principal scientific goal was to learn how
advection and diffusion by these currents determine the shape and amplitude of
the Mediterranean salt tongue. Fourteen floats were launched at a depth of
1100 min a cluster centered on 32N, 24W, and seven other floats were launched
incoherently along a north/south line from 24N to 37N. At the same time
investigators from Scripps Institution of Oceanography and the University of
Rhode Island used four other SOFAR floats to tag a submesoscale lens of
Mediterranean water. Slightly over twenty years of float trajectories were
p reduced during the first year of the experiment.
In this report we briefly describe the 1984 field operations and show the
first year's SOFAR float data. Perhaps the most striking result is that
westward flow within the Mediterranean salt tongue was found to be confined to
a rather narrow jet {roughly 150 km in meridional extent) which had a mean
speed of roughly 2 em s -l. To the north or south of this jet the mean flow
was much weaker and eastward. This suggests that currents associated with the
salt tongue itself {rather than the gyre scale circulation) may be most
important for determining the salt distribution.
1986-07-01T00:00:00Z
Gibraltar experiment : a plan for dynamic and kinematic investigations of strait mixing, exchange and turbulence
Bryden, Harry L.
Kinder, Thomas H.
http://hdl.handle.net/1912/7955
2016-04-22T13:01:25Z
1986-08-01T00:00:00Z
Gibraltar experiment : a plan for dynamic and kinematic investigations of strait mixing, exchange and turbulence
Bryden, Harry L.; Kinder, Thomas H.
The flow through the Strait of Gibraltar has always held a special
fascination for oceanographers. Attempts to understand and measure the
strong currents in the Strait stimulated many of the early advances in
oceanography (Deacon, 1971). Over the centuries, the focus of scientific
investigations has shifted from understanding how the mass budget of the
Mediterranean is maintained in the presence of the strong inflow of
Atlantic water through the Strait of Gibraltar, to observing the outflow of
Mediterranean water over the Gibraltar sill, to measuring the two-layer.
exchange of Atlantic inflow and Mediterranean outflow through the Strait.
In the past few years the focus has again shifted to the study of how the
dynamical constraints for flow through a narrow and shallow strait act to
control the amount of exchange between the Atlantic and Mediterranean
basins. To investigate the dynamics of flow through a strait, a year-long
field experiment has been designed to measure the flows through the Strait
of Gibraltar, including their time variability over tidal to seasonal time
scales, and to assess the importance of friction, mixing, rotation, and
nonlinear processes in controlling the exchange through the Strait. This
field program, called the Gibraltar Experiment, will be carried out by a
group of American, Spanish, Moroccan, Canadian and French scientists during
the period from Fall 1985 to Fall 1986.
1986-08-01T00:00:00Z
Exploring practical estimates of the ensemble size necessary for particle filters
Slivinski, Laura
Snyder, Chris
http://hdl.handle.net/1912/7948
2016-04-19T07:47:42Z
2015-11-11T00:00:00Z
Exploring practical estimates of the ensemble size necessary for particle filters
Slivinski, Laura; Snyder, Chris
Particle filtering methods for data assimilation may suffer from the “curse of dimensionality,” where the required ensemble size grows rapidly as the dimension increases. It would, therefore, be useful to know a priori whether a particle filter is feasible to implement in a given system. Previous work provides an asymptotic relation between the necessary ensemble size and an exponential function of , a statistic that depends on observation-space quantities and that is related to the system dimension when the number of observations is large; for linear, Gaussian systems, the statistic can be computed from eigenvalues of an appropriately normalized covariance matrix. Tests with a low-dimensional system show that these asymptotic results remain useful when the system is nonlinear, with either the standard or optimal proposal implementation of the particle filter. This study explores approximations to the covariance matrices that facilitate computation in high-dimensional systems, as well as different methods to estimate the accumulated system noise covariance for the optimal proposal. Since may be approximated using an ensemble from a simpler data assimilation scheme, such as the ensemble Kalman filter, the asymptotic relations thus allow an estimate of the ensemble size required for a particle filter before its implementation. Finally, the improved performance of particle filters with the optimal proposal, relative to those using the standard proposal, in the same low-dimensional system is demonstrated.
Author Posting. © American Meteorological Society, 2015. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Monthly Weather Review 144 (2016): 861-875, doi:10.1175/MWR-D-14-00303.1.
2015-11-11T00:00:00Z