A two-layer model for the separation of inertial boundary currents

1. Introduction The problem of the steady circulation in an inviscid, two-layer ocean is solved in the limit of small mid-oceanic Ross by number. The model is not new. Certain aspects of the problem have been treated by Fofonoff (1954 and 1962), Deacon et al (1955), Charney (1955), Morgan (1956), Stammel (1958), Robinson (1963), Blandford (1965), J acobs (1968), and Schmitz (1969)

Effects of remote annual forcing in the eastern tropical Atlantic Ocean

An ocean model is used to study the effects of remote annual forcing in the eastern tropical Atlantic. The model is linear, viscid and continuously stratified. The ocean basin is an idealized version of that of the tropical Atlantic, and the wind stress forcing the model is an idealized representation of the annual variation of the equatorial trades in the western Atlantic. Solutions are represented as expansions of the baroclinic modes of the system. The response of each mode is found numerically, not by integrating the equations of motion forward in time, but at a fixed frequency (2π year–1) using techniques that are typically used in models of the tides. Prominent features of the solution are the following. When the remote trades strengthen, sea level drops and the pycnocline rises markedly throughout the Gulf of Guinea. At 4W the annual response is tightly trapped to the equator and to the coast of Africa near 5N. In contrast, the response propagates offshore along the southern coast of Africa near 10E. Events propagate upward everywhere in the Gulf of Guinea and poleward (nearly) everywhere along the coast of Africa. These features compare favorably with observations. A single baroclinic mode does not dominate the response. Instead, waves associated with several modes superpose to form beams that propagate energy vertically as well as horizontally (McCreary, 1984). Along the equator the response is predominantly a combination of a beam of equatorial Kelvin waves and a lowest order (l – 1) Rossby beam. Along the coast of Africa at 5N it is primarily a beam of coastal Kelvin waves

Summability methods for hermite functions

Many problems in equatorial oceanography can be analytically solved via series of Hermite functions, but unfortunately these expansions converge very poorly. In this note, we describe two simple tricks for accurately evaluating such series. The first, due to Moore, is to apply numerical weighting factors to the last four terms in the series. This is a special case of a more powerful technique known as the `Euler-Abel' method which is almost as easy to apply. Our numerical examples show that both methods are very effective. The Euler-Abel method gives an error which decreases exponentially fast as N, the number of terms retained in the truncated series, increases. Moore's method only reduced the error by a factor of 0(1/N2) in comparison to the original series, but this is more than enough for most practical purposes, and this trick is simpler and distributes the error more uniformly in latitude than the Euler-Abel transformation. A conservative rule-of-thumb is that both methods give errors too small to observe on a graph on the range where N is the number of terms in the Hermite series.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26266/1/0000351.pd

A Note on Low-Frequency Equatorial Basin Modes

A new low-frequency standing equatorial wave mode is described. It is composed solely of long Kelvin and Rossby waves, whereas previously described low-frequency modes involved short, eastward propagating Rossby waves. It is argued that these short waves travel too slowly to allow such modes to set up. A simple closed form expression is given for the new basin mode; this is also a new form for the sum of a Kelvin wave and its eastern boundary reflection

The Environmental Dependence of the Evolving S0 Fraction

We reinvestigate the dramatic rise in the S0 fraction, f_S0, within clusters since z ~ 0.5. In particular, we focus on the role of the global galaxy environment on f_S0 by compiling, either from our own observations or the literature, robust line-of-sight velocity dispersions, sigma's, for a sample of galaxy groups and clusters at 0.1 < z < 0.8 that have uniformly determined, published morphological fractions. We find that the trend of f_S0 with redshift is twice as strong for sigma < 750 km/s groups/poor clusters than for higher-sigma, rich clusters. From this result, we infer that over this redshift range galaxy-galaxy interactions, which are more effective in lower-sigma environments, are more responsible for transforming spiral galaxies into S0's than galaxy-environment processes, which are more effective in higher-sigma environments. The rapid, recent growth of the S0 population in groups and poor clusters implies that large numbers of progenitors exist in low-sigma systems at modest redshifts (~ 0.5), where morphologies and internal kinematics are within the measurement range of current technology.Comment: Accepted for publication in The Astrophysical Journal. 13 pages, 6 figure

Bridging the Gap between Earth Science and Students: An Integrated Approach using NASA Earth Science Climate Data

Under the auspices of the Department of Education's No Child Left Behind (NCLB) Act, beginning in 2007 students will be tested in the science area. There are many techniques that educators can employ to teach students science. The use of authentic materials or in this case authentic data can be an engaging alternative to more traditional methods. An Earth science classroom is a great place for the integration of authentic data and science concepts. The National Aeronautics and Space Administration (NASA) has a wealth of high quality Earth science data available to the general public. For instance, the Atmospheric Science Data Center (ASDC) at NASA s Langley Research Center houses over 800 Earth science data sets related to Earth's radiation budget, clouds, aerosols and tropospheric chemistry. These data sets were produced to increase academic understanding of the natural and anthropogenic factors that influence global climate; however, a major hurdle in using authentic data is the size of the data and data documentation. To facilitate the use of these data sets for educational purposes, the Mentoring and inquirY using NASA Data on Atmospheric and Earth science for Teachers and Amateurs (MY NASA DATA) project has been established to systematically support educational activities at all levels of formal and informal education. The MY NASA DATA project accomplishes this by reducing these large data holdings to microsets that are easily accessible and explored by K-12 educators and students though the project's Web page. MY NASA DATA seeks to ease the difficulty in understanding the jargon-heavy language of Earth science. This manuscript will show how MY NASA DATA provides resources for NCLB implementation in the science area through an overview of the Web site, the different microsets available, the lesson plans and computer tools, and an overview of educational support mechanisms

Differential binding of neutralizing and non-neutralizing antibodies to native-like soluble HIV-1 Env trimers, uncleaved Env proteins, and monomeric subunits

Background: The trimeric envelope glycoproteins (Env) on the surface of HIV-1 virions are the targets for neutralizing antibodies (NAbs). No candidate HIV-1 immunogen has yet induced potent, broadly active NAbs (bNAbs). Part of the explanation may be that previously tested Env proteins inadequately mimic the functional, native Env complex. Trimerization and the proteolytic processing of Env precursors into gp120 and gp41 profoundly alter antigenicity, but soluble cleaved trimers are too unstable to serve as immunogens. By introducing stabilizing mutations (SOSIP), we constructed soluble, cleaved Env trimers derived from the HIV-1 subtype A isolate BG505 that resemble native Env spikes on virions both structurally and antigenically. Results: We used surface plasmon resonance (SPR) to quantify antibody binding to different forms of BG505 Env: the proteolytically cleaved SOSIP.664 trimers, cleaved gp120-gp41ECTO protomers, and gp120 monomers. Non-NAbs to the CD4-binding site bound only marginally to the trimers but equally well to gp120-gp41ECTO protomers and gp120 monomers, whereas the bNAb VRC01, directed to the CD4bs, bound to all three forms. In contrast, bNAbs to V1V2 glycan-dependent epitopes bound preferentially (PG9 and PG16) or exclusively (PGT145) to trimers. We also explored the antigenic consequences of three different features of SOSIP.664 gp140 trimers: the engineered inter-subunit disulfide bond, the trimer-stabilizing I559P change in gp41ECTO, and proteolytic cleavage at the gp120-gp41ECTO junction. Each of these three features incrementally promoted native-like trimer antigenicity. We compared Fab and IgG versions of bNAbs and validated a bivalent model of IgG binding. The NAbs showed widely divergent binding kinetics and degrees of binding to native-like BG505 SOSIP.664. High off-rate constants and low stoichiometric estimates of NAb binding were associated with large amounts of residual infectivity after NAb neutralization of the corresponding BG505.T332N pseudovirus. Conclusions: The antigenicity and structural integrity of cleaved BG505 SOSIP.664 trimers render these proteins good mimics of functional Env spikes on virions. In contrast, uncleaved gp140s antigenically resemble individual gp120-gp41ECTO protomers and gp120 monomers, but not native trimers. Although NAb binding to functional trimers may thus be both necessary and sufficient for neutralization, the kinetics and stoichiometry of the interaction influence the neutralizing efficacy of individual NAbs