196,211 research outputs found
Heat budgets and diurnal mixing in the western equatorial Pacific Ocean
No full textThis thesis presents a study of upper ocean processes effecting the heat content and sea surface temperature of the western equatorial Pacific Ocean. The study uses high resolution ship-borne measurements of upper ocean hydrography and current structure, and simultaneous measurements of air/sea fluxes of heat, moisture and momentum. Two periods are investigated, (1) April 1988 and, (2) December 1992- February 1993. Methods of analysis are heat budget estimation of the two data sets and one dimensional numerical mixing model experiments. The second heat budget shows that over the period December 1992-February 1993 the heat balance is between the net surface heat flux and the local change in heat content of the upper 40 m to within 10 W m~2. Exceptions to this local balance are of short duration, order(days), and of large amplitude, order(100 W m~2). During April 1988 the local change in heat content is found to be dominated by horizontal advection down to 200 m. The net surface heat flux is found to be balanced by an estimate of vertical turbulent diffusion of heat to within 10%. Evidence is presented, using a combination of observations and numerical simulations, showing sub- surface density structure to interact with the mixed layer in such a way as to effect the sea surface temperature. One dimensional mixing models are shown to be able to simulate the observed diurnal cycle of mixing in the upper ocean. Sensitivity studies show the diurnal momentum cycle to be sensitive to vertical velocity shear and the value of the Coriolis parameter, /, and relatively insensitive to the zonal pressure gradient. The diurnal thermal cycle is shown to be sensitive to short wave radiation, and to a lesser extent latent heat loss. Mixing models are used to investigate the effects of precipitation on the sea surface temperature. Rain is shown to depress the sea surface temperature by up to 0.3 degree C immediately following a rain event, but after a period of weeks there is an increase in sea surface temperature, caused by local barrier layer formation. For a simulation of the period December 1992-February 1993 the increase is small (0.05 degree C). Implications of the work for general circulation modelling are discussed.</p
The diurnal mixed layer and upper ocean heat budget in the western equatorial Pacific
No full textThis paper presents the results of an experiment in the western equatorial Pacific centered on the equator at 165°E which was designed to study the changes to the structure of the upper ocean on timescales of a few days and spatial scales of tens of kilometers. The results show that the response of the upper ocean to atmospheric forcing is very sensitive to the vertical structure of both the temperature and salinity. The diurnal response of the near-surface temperature to daytime heating and nighttime cooling was found to have an amplitude of a few tenths of a degree Celsius, This compares with a horizontal variation of temperature on scales of a few tens of kilometers of a similar magnitude. Even away from the very fresh surface layers typical of the area, salinity is found to play an important role in limiting the depth of nighttime mixing. In this case a subsurface salinity maximum restricts the depth to around 40 m. The nighttime convection is severely limited by either a small change in the surface forcing or the horizontal advection of slightly cooler waters from the east; we are unable to determine which is the dominant mechanism in the present case. The reduced mixing leads to an increase of the diurnal variation of sea surface temperature to over 1°C. The estimated net surface heat flux from the atmosphere to the ocean was found to be not significantly different from zero at 10 W m?2, in agreement with recent measurements. The net surface heat flux during the period of the heat budget experiment, which took place on the equator, was substantially higher at 65 W m?2. Changes of in situ temperature are found to be dominated by advection. The vertical velocity is estimated to be of order 10 m d?1 and to be caused by advection along east-west sloping density surfaces. Changes to the temperature structure of the upper ocean induced by motions with a timescale of a few days (possibly planetary waves) are found to be significantly greater than longer-term wind-induced upwelling or advectio
Glider observations of enhanced deep water upwelling at a shelf break canyon: a mechanism for cross-slope carbon and nutrient exchange
No full textUsing underwater gliders we have identified canyon driven upwelling across the Celtic Sea shelf-break, in the vicinity of Whittard Canyon. The presence of this upwelling appears to be tied to the direction and strength of the local slope current, which is in itself highly variable. During typical summer time equatorward flow, an unbalanced pressure gradient force and the resulting disruption of geostrophic flow can lead to upwelling along the main axis of two small shelf break canyons. As the slope current reverts to poleward flow, the upwelling stops and the remnants of the upwelled features are mixed into the local shelf water or advected away from the region. The upwelled features are identified by the presence of sub-pycnocline high salinity water on the shelf, and are upwelled from a depth of 300 m on the slope, thus providing a mechanism for the transport of nutrients across the shelf break onto the shelf
Dr. Duane M. Jackson, Morehouse College, July 2011
No full textThis video is a conversation with Dr. Duane M. Jackson. Dr. Jackson talks about his paper, "Recall and the Serial Position Effect: The Role of Primacy and Recency on Accounting Students' Performance." Jackie Daniel, AUC Woodruff Library, is the interviewer
The ECO-MAR (Ecosystem of the Mid-Atlantic Ridge at the Sub-Polar Front and Charlie Gibbs Fracture Zone) project: description of the benthic sampling programme 2007–2010
No full textThe ECOMAR project conducted 4 cruises to the Mid-Atlantic Ridge (MAR) in the summer months of the years 2007–2010 making repeat visits to 4 stations at 2500 m depth on the flanks of the MAR; a pair of northern stations at 54°N and southern stations at 49°N. Swath bathymetry surveys across the ridge revealed a pattern of sediment-covered flat terraces parallel to the axis of the MAR with intervening steep rocky slopes. Benthic fauna were sampled by otter trawl, megacorer and a suite of tools carried by the ROV Isis including push cores, grabs and suction sampler. Video and photo surveys were done using the SHRIMP towed vehicle and ROV Isis. Additional surveying and sampling was done at 1050–822 m depth across the summit of a seamount located at 48°44′N, 28°10′W on the western crest of the MAR between the two southern stations
"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States" By M. Carey.
No full text"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States: containing bried sketches of the moral and political character of those states.
By M. Carey, member of the American philosophical, and of the American Antiquarian Society, and author of The Olive Branch, Cindiciae Hibernicae, essays on banking, on political economy, and on internal improvement.
To which are now added the English editor's comments on the subject; together with Important Advice to Emigrants, and Cautions Against Impositions Practiced in the Outports
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Dr. Glendon Swarthout
No full textHosted by Roger M. Busfield, MSU Assistant Professor of Speech and Theater, Meet the Author is designed to introduce a general audience to a contemporary author and their work through in-depth interviews. This episode features a conversation between Dr. Glendon Swarthout, prolific author and English professor at MSU, and assistant professors Sam S. Baskett and Theodore B. Strandness
Simulation of thermal plant optimization and hydraulic aspects of thermal distribution loops for large campuses
No full textFollowing an introduction, the author describes Texas A&M University and its utilities system. After that, the author presents how to construct simulation models for chilled water and heating hot water distribution systems. The simulation model was used in a $2.3 million Ross Street chilled water pipe replacement project at Texas A&M University. A second project conducted at the University of Texas at San Antonio was used as an example to demonstrate how to identify and design an optimal distribution system by using a simulation model. The author found that the minor losses of these closed loop thermal distribution systems are significantly higher than potable water distribution systems. In the second part of the report, the author presents the latest development of software called the Plant Optimization Program, which can simulate cogeneration plant operation, estimate its operation cost and provide optimized operation suggestions. The author also developed detailed simulation models for a gas turbine and heat recovery steam generator and identified significant potential savings. Finally, the author also used a steam turbine as an example to present a multi-regression method on constructing simulation models by using basic statistics and optimization algorithms. This report presents a survey of the author??s working experience at the Energy Systems Laboratory (ESL) at Texas A&M University during the period of January 2002 through March 2004. The purpose of the above work was to allow the author to become familiar with the practice of engineering. The result is that the author knows how to complete a project from start to finish and understands how both technical and nontechnical aspects of a project need to be considered in order to ensure a quality deliverable and bring a project to successful completion. This report concludes that the objectives of the internship were successfully accomplished and that the requirements for the degree of Degree of Engineering have been satisfied
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