bluuebunny/crossref_metadata_2025 huggingface dataset:
Replacement of traditional lectures with computer-based tutorials: a case study
Authors: Lavelle Derek
Published: January 2012

This paper reports on a pilot project with a group of 60 second-year undergraduates studying the use of standard forms of contract in the construction industry. The project entailed the replacement of two of a series of nine scheduled lectures with a computer-based tutorial. The two main aims of the project were to test the viability of converting existing lecture material into computer-based material on an in-house production basis, and to obtain feedback from the student cohort on their behavioural response to the change in media. The effect on student performance was not measured at this stage of development.DOI:10.1080/0968776960040115
Needs before means: the dialectics of learning and technology
Authors: King Anny , Honeybone Andrew
Published: January 2012

Higher education and society in general are changing rapidly. The student body is more diverse and larger. Arguments rage about the vocational relevance of higher education. The unit of resource is declining. The way ahead appears fraught with difficulty. However, computer-based technology is advancing at breakneck speed. Is it the 5th Cavalry charging to the rescue of the beleaguered educational troops? The argument that will be advanced in this paper is that such a view is simplistic. The key issue is that pedagogic purposes and individual student needs should be first defined so as to identify the best means of meeting those purposes and needs. The general argument that dialogue based on dialectical communication lies at the heart of the learning process will then be applied to the use of learning technology in language learning. It will be demonstrated how, through a dialectical process, the appropriate use of learning technologies in meeting students' changing needs can be progressively refined.DOI:10.1080/0968776960040202
Computer-based laboratory simulation: evaluations of student perceptions
Authors: Edward Norrie S.
Published: January 2012

Laboratory experimentation in engineering is an essential part of the three main components in an engineer's formation. The theoretical constructs and models are imparted in lectures and tutorials. Workshop hands-on activity allows the student to acquire an understanding of the interaction of design and manufacture, and the constraints both impose. Characteristics of plant are investigated through experiment, and this aids the learner's understanding of the limitation of models in predicting performance. The learner also gains an appreciation of the nature of errors and of the construction of plant. But while the oil industry has brought prosperity to the North- East, it has also brought unique educational demands: the working arrangements place severe restrictions on part-time student attendance. Technicians work a block of two to four weeks offshore, followed by a similar period of leave. Different companies have different arrangements, and shift-change days.DOI:10.1080/0968776960040306
Using computer-based tests for information science
Authors: Callear David , King Terry
Published: January 2012

The introduction of objective testing using computer software does not necessarily represent innovative assessment. Where tests occur as an add-on to a course, are timeconstrained, closed-book, invigilated, and where there is little (or no) feedback of results to the students, such testing is best regarded as an innovative technique for traditional summative assessment. A computer-based examination of this nature using the commercial software Question Mark has been operating for a number of years in the Department of Information Science at Portsmouth, in the second-year unit for Logic Programming, with student numbers up to 160.DOI:10.1080/0968776970050105
A critique of the drive towards the globalization of higher education
Authors: Bird David , Nicholson Brian
Published: January 2012

There has been an increase in the level of commerce that transcends national boundaries. Businesses no longer rely on local markets as acceptable, safe areas to do business. The emphasis is on globalization. Failing to globalize will result in the decline of a commercial activity, and a 1990 survey among businesses found that 40 per cent of them considered the expansion of the global market required increased production capacity and speed (Peppard, 1993).DOI:10.1080/0968776980060102
Pre- and post-testing in evaluating a CAL program: preliminary findings
Authors: Wilson Jennifer M. , Lerski Richard A. , Hau Cathryn
Published: January 2012

The aim of this paper is to examine how pre- and post-testing were used in the summative evaluation of the CALRAD (Computer-Assisted Learning for RADiation protection) program. Pre- and post-testing refers to the process whereby an assessment test is given before students use educational materials (pre-test) and after the students have used the materials (post-test). Any change in the students' performance can then be attributed to the use of the educational materials, in this case the CALRAD program. The results may provide information as to whether the program is educationally effective.DOI:10.1080/0968776980060104
Is it sustainable? A comparison of student and tutor online time across three distance-learning courses
Authors: Wilson Tina , Whitelock Denise
Published: January 2012

Computer Mediated Communication (CMC) is a useful pedagogical tool. Mason (1989a) states that it has proved to be 'a life-line to help, information, contact and exchange' for students. Thomas (1989) discusses the benefits of CMC from the tutor and course team perspectives. However, Rumble (1989) discusses the difficulties of costing the introduction of CMC into a course. If more and more distance-learning institutions are going to adopt this medium, it is important to evaluate for all concerned the time required for this type of participation.DOI:10.1080/0968776980060105
Evaluating the impact of Internet provision on students' information-gathering strategies
Authors: Meek Julia , Garnett Marie , Grattan John
Published: January 2012

Universities may invest millions of pounds in the provision of computer hardware without ever seriously considering the educational results such investment may deliver. Equally, academics may be committed to the use of IT in teaching and learning because it is expected of them (cf. Dearing, 1997), and rarely give serious consideration to the impact which the effective use of IT may have on student learning (Lauillard, 1993). The use of the WWW to deliver material in support of university teaching is still in its infancy, yet already two distinct approaches to its use can be seen. The first approach uses the WWW passively to deliver existing lecture notes in a technologically impressive and, perhaps more importantly, highly convenient fashion. The second approach attempts to shape the material delivered to maximize the teaching and learning potential of the WWW and to develop students' skills in the use of the medium. But which approach works more effectively? And how does one balance the needs of an academic community pressured by the Research Assessment Exercise with the need to develop effective teaching and learning strategies which maximize the potential of IT for the academic community, for the students and for their future employers?DOI:10.1080/0968776980060109
Cost-effective support for university students learning via the Web?
Authors: Hawkridge David
Published: January 2012

Academics and other knowledge-owners are creating millions of Webpages that students can use. Universities are teaching more students off-campus because the costs of on-campus provision cannot be met. Offering courses via the Web seems an attractive alternative. Academics (and students) want the courses to be high quality. Yet quality is often lacking. À course outline gets approval, then aims, objectives and content change rapidly during the teaching. Students' and tutors' inputs are seldom monitored. Students join conferences only to discover that few classmates participate actively and the tutors' advice is hard to get. Web courses risk acquiring a poor reputation.DOI:10.1080/0968776980060304
Learning technologies and the lifelong learner: armament or disarmament?
Authors: Seale Jane
Published: January 2012

In a general context, lifelong learning appears to be about increasing access to education and supporting individual development. In the specific context of the United Kingdom, lifelong learning is about converting people to a culture of learning in order that the nation can produce creative, enterprising scholars (Blunkett, 1998). In both contexts, it is considered that learning needs to be a lifelong commitment, in order that individuals can fulfil their potential and improve themselves.DOI:10.1080/0968776990070110
Staff development at RMIT: bottom-up work serviced by top-down investment and policy
Authors: McNaught Carmel , Kennedy Paul
Published: January 2012

What is the business of a university in the 1990s and 2000s? Quantity and quality are both important considerations in modern universities as they seek to maintain important intellectual and physical spaces for their staff to pursue creative research and development, while at the same time needing to provide teaching for escalating numbers of students in all courses in order to shore up funding. These student cohorts have become increasingly diverse (Mclnnis, James and McNaught, 1995) with more part-time students and students from a greater variety of backgrounds. Flexible modes of delivery have been widely viewed as the prime way of meeting the challenges posed by this diversity. There has been a fair amount of naive equating of flexible delivery with production of online materials ('Plug them into the Web') and insufficient attention to the relationship between flexible modes of operation for students, the use of communication and information technologies, and the design of educationally sound learning environments (Kennedy and McNaught, 1997; Reeves and Reeves, 1997). However, there is no doubt that communication and information technologies will be a major part of future university planning, as several recent reports make clear (e.g. Yetton et al., 1997).DOI: 10.1080/0968776000080102
Networked learning in higher education: practitioners' perspectives
Authors: Jones Chris , Asensio Mirea , Goodyear Peter
Published: January 2012

This paper arises from the work of the JISC Committee on Awareness, Liaison and Training (CALT)-funded 'Networked Learning in Higher Education' project. Networked learning is a term that has had a currency for some years now and can be seen as part of the development of a new paradigm in education (Harasim, Hiltz, Teles and Turoff, 1995; Koschmann 1996; Romiszowski and Ravitz, 1997). We have defined networked learning as learning in which C&.IT is used to promote connections: between one learner and other learners; between learners and tutors; between a learning community and its learning resources.DOI:10.1080/0968776000080203
On-line student feedback: a pilot study
Authors: Barnett Liz , Galbraith Jane , Gee Paul , Jennings Fran , Riley Ron
Published: January 2012

Student feedback on courses has been a standard feature of university life for several years, with a substantial research backing to it (see, for example, reviews by Marsh, 1987; Marsh and Dunkin, 1992). Most feedback systems endeavour to serve more than one purpose, with student feedback forming part of the evidence used by: • individual teachers to improve teaching • heads of departments to monitor and guide individual teachers, especially part-time teachers; • course leaders for course development; • senior managers to make decisions on probation and promotion related to teaching performance; consider changes to the wider learning environment; help with the marketing of programmes; • external agencies to assess quality of provisionDOI:10.1080/0968776010090303
Quartz Contents of Pelagic Sediments of the Pacific Ocean
Authors: Rex Robert W. , Goldberg Edward D.
Published: January 2012

The quartz contents of pelagic clays from the Eastern Pacific Ocean show a marked latitudinal dependence with a maximum around 30°N. Present evidence indicates that the quartz is mainly transported to the deposits through the atmosphere and that the observed distribution is probably related to the latitudinal values of the atmospheric wind fluxes and exposed arid land areas. A number of sediments display a distinct change in quartz content with depth. In all cases there is a marked decrease going from the recent to the older strata. It is suggested that the changes indicate a major climatic change that occured sometime during the Late Tertiary.
On the Global Balance of Water Vapor and the Hydrology of Deserts
Authors: Starr V. P. , Peixoto J. P.
Published: January 2012

An attempt is made to measure the horizontal divergence of the vertically integrated moisture flux over the northern hemisphere for the calendar year of 1950. This is done through the evaluation of daily data for some 90 upper air stations at several levels up to 500 mb. The final map obtained indicates strong maxima of divergence not only over certain oceanic regions, but also over three separate arid regions. Such a result implies an unexpectedly large excess of evaporation over precipitation in these latter areas, which must be balanced by convergence of liquid water on and below the ground surface, unless the year studied was rather completely different from normal, this not being so likely, however.
Liquid Water Content and the Adiabatic Model of Cumulus Development
Authors: Warner J. , Squires P.
Published: January 2012

The literature shows considerable disagreement concerning the liquid water contents found in cumuliform cloud and the relation of observed values to those deduced from the adiabatic model. The present paper describes some observations in which two methods of measuring liquid water have been used simultaneously and found to be in good general agreement. However, the two methods employed very different averaging periods, so that individual measurements were not strictly comparable. These results, and the observations of other workers, are discussed in relation to the general level of liquid water in cumuliform cloud and its variability in space.
Natural Sources of Gaseous Pollutants in the Atmosphere
Authors: Altshuller Aubrey P.
Published: January 2012

Various gaseous pollutants including ozone, nitrous oxide, nitric oxide, nitrogen dioxide, methane, hydrogen, formaldehyde, ammonia, hydrogen sulfide, mercaptans, chlorine compounds and free radicals can be formed by natural processes such as ultraviolet photochemical processes in the upper atmosphere and microbiological processes. The modes of formation and destruction of these gases, especially of their concentrations in the atmosphere, and the various reactions in which these gases can participate with each other are discussed in detail.
Computations of the Growth by Condensation of a Population of Cloud Droplets
Authors: Mordy W.
Published: January 2012

The number and size of cloud droplets formed on several condensation nucleus spectra is computed numerically. The relative humidity is treated as a dependent variable and the settling of droplets by Stokes Law is accounted for. A model is presented for studying simultaneous variations in vertical velocity, nucleus distribution, and humidity by the use of an electronic computer. To date eight computations have been made for three types of nucleus spectra at different rates of rise. Both nucleus distribution and rate of rise produce significant differences in resulting cloud droplet distributions. The concentration of cloud droplets computed ranges from 1 cm–3 to 470 cm–3 for vertical velocities ranging from 5 cm/sec to 100 cm/sec.
The Formation of Rain by Coalescence in Very Shallow Cumulus
Authors: Mason B. J.
Published: January 2012

It is demonstrated theoretically that showers may be released by coalescence from shallow cumulus, only 1 km deep, lasting for one hour and having cloud-droplet spectra typical of those measured in clouds formed in clean, maritime air. In clouds formed in more heavily polluted continental air and which have higher concentrations of smaller cloud droplets, the coalescence process is delayed and retarded so that, under otherwise comparable conditions, the time required for shower formation is considerably increased.
The Oceanic Thermocline and the Associated Thermohaline Circulation
Authors: Robinson Allan , Stommel Henry
Published: January 2012

A study is made of the thermal structure of an ocean which is dynamically geostrophic, bounded by an eastern coast, and driven by an imposed surface temperature distribution and wind-stress. The heat equation contains vertical diffusion in the form of a virtual eddy mixing parameter and non-linear terms of vertical and north-south advection. Comparison of the results with the North Atlantic shows an agreement with the observed temperature distribution in the thermocline region, including the deepening of isotherms in mid-latitudes. The value of the vertical component of velocity at the bottom of the thermocline is predicted, and a numerical value for the eddy-conductivity obtained.
On a Graphical Method for an Approximate Determination of the Vertical Velocity in the Mid-Troposphere
Authors: Wiin-Nielsen A.
Published: January 2012

A simple graphical method for determining the vertical velocity from a simplified, but consistent form of a diagnostic equation for this quantity is developed. It is shown that the main term in the equation is the advection of temperature in the vorticity field. Section 2 contains simple rules from which the sign of the vertical velocity may be determined. An approximate solution to the equation is found in section 3, while section 4 contains an investigation of the accuracy of this solution as function of the scale of the motion. Different types of approximate solutions are investigated. Section 5 contains an example of the use of the method.
A Radio-Active Fall-Out Study at Melbourne, Australia
Authors: Dyer A. J. , Yeo Miss S-A.
Published: January 2012

Measurements of the radio-active fall-out occurring in weekly rainfall samples at Melbourne (Aspendale) are presented for the period June 1958 to February 1959. Radio-active decay analyses show the activity to have arisen from nuclear weapons tests carried out near the equator during the period April to September 1958. The results indicate that, despite presumably continuous dispersion, individual radio-active clouds maintain their discreteness and a limited E—W extent even after six or nine months residence in the stratosphere. This property allows a poleward drift speed of order 1 m/sec and zonal circulation velocities ranging from 6 to 17 m/sec to be inferred.
The Atmospheric Budget of Angular Momentum
Authors: Tucker G. B.
Published: January 2012

The mean meridional circulation derived from wind observations is combined with surface torque and mountain torque measurements to obtain a complete angular momentum budget for the northern Hemisphere between 15°N and 70°N for summer and winter. A previously proposed scheme of vertical flux of angular momentum involving downward flux everywhere except in the lower layers of the tropical easterlies is confirmed. The layer of zero vertical flux in the tropics is approximately at the level of maximum easterly wind.
The Effect of Monochromatic Light on the Concentration of Large Ions
Authors: Elnadi A. F. , Farag N.
Published: January 2012

The divided electrode condenser is used to study the effect of monochromatic light of wave lengths between 4,030 and 6,610 Å (using 10 interference filters of Jena glass), on the concentration of large ions having mobilities below 10 × 10–4 cm/sec: volt/cm.

The number of ions per C.C. is measured with the aid of the characteristics obtained for each wave length, at different group mobilities, both in the presence of light (N1) and in complete darkness (N2). The ratio (N1/N2) is obtained for each filter and for the four mobility groups, i.e. 6.90 × 10–4, 2.22 × 10–4, 1.02 × 10–4 and 0.60 × 10–4 cm/sec. : volt/cm.

The results are discussed on the basis of statistical analysis by applying the correlation and significance tests.
Energy and Numerical Weather Prediction
Authors: Lorenz Edward N.
Published: January 2012

Since the study of energy transformations and the numerical integration of simplifiied equations are sometimes used as alternative approaches to the same physical problem, it is often desirable that the simplified equations conserve total energy under reversible adiabatic processes. Preferably, the equations should also conserve the sum of kinetic energy and available potential energy, and they should describe the tendency for static stability to increase as kinetic energy is released.

It is found that if the equation of balance is used as a filtering approximation, all the terms in the vorticity equation which involve both the rotational and the divergent part of the wind field should be retained, while, if the geostrophic equation is used, all of these terms in the vorticity equation should be omitted, if the equations are to possess suitable energy invariants.

An n-layer model with the appropriate energy invariants is developed. The two-layer model may be the simplest possible model with variable static stability. The model appears to be suitable for theoretical studies of the general circulation.
The Production Rate of Natural Tritium
Authors: Craig Harmon , Lal Devendra
Published: January 2012

A detailed evaluation is made of the production rate of natural tritium in the pre-thermonuclear epoch. Deuterium and tritium analyses on the same precipitation samples are used to establish the uncontaminated tritium levels in precipitation sampled before the Castle tests, and the tritium balance is calculated for the North American troposphere. The global mean production rate Q̅, calculated from the geochemical inventory, is found to be 0.5 ± 0.3 atoms T/cm2 sec. This value is three to four times smaller than values found previously by such calculations because of the following developments:

The deuterium and tritium data show that the increases in tritium content observed during early thermonuclear tests before Castle are due to addition of synthetic tritium rather than to random fluctuations. The deuterium-tritium relationships are used to establish the general pattern of tritium variations over the North American continent and to evaluate the uncontaminated tritium levels.

The mean stratospheric residence time for tritium is found to be about 1.6 years from studies on fission product fallout and from the latitudinal variation of stratospheric cosmic ray production.

Stratospheric tritium is preferentially injected into the troposphere at high latitudes, as shown by fallout observations. The tritium influx into the North American troposphere is therefore higher than the mean global value.

The predicted production rate is calculated from cosmic ray and nuclear cross section data using the star production rates in the atmosphere. The predicted mean global tritium production rate during an average solar cycle is found to be 0.25 ± 0.08 atoms T/cm2 sec. The variation in the production rate over an average solar cycle is found to be ± 4.5 %.

Within the uncertainties of the data and calculations, the production rates calculated from the geochemical inventory and from the cosmic ray data are in agreement, and there is thus no observational evidence for accretion of tritium from an extra-terrestrial source.
Experimentally Observed Instability of a Laminar Ekman Flow in a Rotating Basin
Authors: Arons A. B. , Ingersoll A. P. , Green III T.
Published: January 2012

In studying the axi-symmetric flow induced by source-sink distributions in a rotating cylindrical basin in the absence of radial barriers, a highly organized pattern of instability has been observed in the laminar Ekman layer along the bottom of the basin. The instability manifests itself in the form of almost perfectly concentric cylindrical sheets or curtains of water which rise as sharply defined vertical jets from the Ekman layer and penetrate the entire depth of fluid. A less sharply defined downward motion between the curtains completes the circulation celis thus developed. At some maximum critical radius, the curtains usually disappear, and the flow at larger radii is a stable, laminar Ekman flow. Quantitative observations of ring spacing and critical radius are reported for experiments in which angular velocity, flow rate, viscosity and total depth of water were varied over experimentally available ranges.
Cloud Patterns in Hurricane Daisy, 1958
Authors: Malkus Joanne S. , Ronne Claude , Chaffee Margaret
Published: January 2012

Maps of clouds in Hurricane Daisy, 1958, have been constructed from aerial ciné photographs made by the aircraft of the National Hurricane Research Project of the U.S. Weather Bureau. Films suitable for quantitative analysis were available for four flights on three separate days during the formation, deepening, and maturity of this small but intense Atlantic hurricane which moved slowly over the ocean in the vicinity of 30° N, 76° W. Clouds were located within 5–10 nautical miles relative to the known aircraft path (in coordinates with origin at hurricane center) by a modified method of aerial photogrammetry using the accurately known timer for the image to cross a frame. Horizontal and vertical dimensions of important clouds and cloud forms have been measured to within about 10 %.

The photographic maps are compared to radar analyses made from the same and also different aircraft (U.S. Navy WV-4). The most significant results are first the remarkable persistence of recognizable cloud patterns throughout the three days studied, during which the storm deepened and moved about 200 nautical miles and second, the concentration of convective activity into a few lines of cumulonimbus towers which even on the mature day occupied only about 4 % of the rain area (radius within about 200 nautical miles).
On the Steady Flow of a Fluid of Variable Density Past an Obstacle
Authors: Drazin Philip G.
Published: January 2012

A model of steady airflow past a three-dimensional mountain is considered. The fluid is inviscid and incompressible. The flow is under the influence of gravity, but for most of the work the earth's rotation is neglected. Far upstream the flow is parallel and horizontal, the velocity U(z) and the density ƍ(z) varying with height z. By use of conservation of density and head along streamlines, and thence of the dependence of density and head on one variable z0 only, the equations of motion are simplified, z0 (r) being the height far upstream of the streamline through the point with position vector r. The flow is considered first with small and then with large density variations far upstream. In the case when these variations are small, results of the known method of simple-shear secondary flows are rederived and extended.

The chief consideration of this paper is the buoyancy effects of large variations of density in the oncoming stream. For simplicity, the shear far upstream is neglected. The primary and secondary velocities are found for large Richardson number (proportional to gdƍ/ƍdz0). The method is time-symmetric and analogous to taking the first two terns of the Janzen-Rayleigh expansion, the inverse of the Richardson number being the analogue of the square of the Mach number. The primary velocity, for infinite buoyancy forces, is horizontal, the flow in each horizontal plane being the same as the potential flow about the section of the obstacle in that plane. In general there is shear between horizontal planes, with horizontal primary vorticity. The secondary flow is found explicitly for a circular cylinder with vertical axis and for a hemisphere resting in a horizontal plane. The secondary approximation is not uniformly valid near the horizontal plane at the height of the top (if any) of the obstacle. Near that plane there is an inviscid shear layer, and the velocity gradient cannot be neglected, however large the Richardson number.
Temperature and Steady State Vertical Heat Flux in the Ocean Surface Layers
Authors: Kraus Eric B. , Rooth Claes
Published: January 2012

The occurrence of a quasi-isothermal surface layer is shown to be a necessary consequence of the vertical distribution of heat sources and sinks, which requires an upward transport of heat. The depth of the convective layer depends essentially on a balance between the absorption of visible radiation within the layer and the loss of heat at the surface. Variations in the profile below the isothermal layer are primarily caused by vertical motion. Numerical examples illustrate the effects of meteorological conditions on the heat loss and hence on the surface temperature and thermal structure below.
Thermohaline Convection with Two Stable Regimes of Flow
Authors: Stommel Henry
Published: January 2012

Free convection between two interconnected reservoirs, due to density differences maintained by heat and salt transfer to the reservoirs, is shown to occur sometimes in two different stable regimes, and may possibly be analogous to certain features of the oseanic circulation.
The Effect of Meanders on the Kinetic Energy Balance of the Gulf Stream
Authors: Webster Ferris
Published: January 2012

Calculations have been made, using surface velocity observations, of the horizontal transfer of kinetic energy from meanders to mean flow at two separate localities in the Gulf Stream System. In both cases, it was found that there was a surface flow of kinetic energy from the meanders to the mean flow, exactly opposite to what would be expected if the meanders were frictionally driven. The observations suggest that the meanders derive energy from sources other than the kinetic energy of the mean flow. The role of the meanders in relation to the mean Gulf Stream appears analogous to that of large-scale eddies in relation to the general circulation of the atmosphere.
Convection in Conditionally Unstable Atmosphere
Authors: Kuo H. L.
Published: January 2012

The analysis has shown that if the stratification is unstable for ascending motion over an infinite area and stable for descending motion, and small random perturbations of various scales are introduced, the final disturbance evolved will have the dimension of a cumulus cloud. The stable stratification in the descending region has the effect of increasing the critical lapse-rate and narrowing the ascending region and making the descending motion widespread, so that the centers of the ascending regions are further apart. The distance estimated from the theoretical analysis agrees favorably with those obtained from satellite observations.

The distributions of the various perturbation quantities pertaining to a circular symmetrical disturbance have been obtained. They show many resemblances to the corresponding distributions in tropical storms. Since the main source of energy of the mature tropical storms is the latent heat of condensation, it is really tempting to attribute the formation of these large-scale disturbances directly to convection in conditionally unstable air. However, the analysis shows that some organizing mechanisms are needed in order to channel the release of the energy of unstable stratification into a large scale circulation.
The Stability of Thermoclinic Jets
Authors: Stern Melvin E.
Published: January 2012

A laminar jet, in a “shallow layer” of water of density ϱ – Δϱ is in geostrophic equilibrium above a much deeper and resting layer of water of density ϱ. We compare the quasi-hydrostatic energy releasing process in this thermoclinic model with other baroclinic and barotropic models. It is first shown that a small amplitude disturbance can grow only if there is a transfer of kinetic energy from the horizontal variations in the mean jet and that conversions of mean potential energy can only occur concomitantly with, or as a finite amplitude result of this process. We also examine the perturbation equation for values of the stream Rossby number which are much less than unity and show that the finite depth of the thermocline inhibits inflectional instability of the jet. The generalization of Lord Rayleigh‘s theorem shows that the jet is stable if the gradient of potential vorticity does not vanish. In general, there is a critical value of the ratio of the radius of deformation (f–1 √gH0Δϱ/ϱ) to the half width of the jet above which quasigeostrophic disturbances will start to grow. It is proposed that meanders of the synoptic Gulf Stream will develop when the jet becomes “excessively” deep and that the effect of such instabilities is to limit the depth of the main thermocline in the interior of the ocean.
On the theory of the general circulation of the atmosphere
Authors: Adem Julián
Published: January 2012

Applying the conservation of energy principle to the incoming solar radiation and to the long-wave radiation, a heating mechanism of the atmosphere is introduced. A simplified emission spectrum of the atmosphere with one transparent region is used. The surface of the earth and a cloud layer are considered as black bodies.

A simplified model of the atmosphere containing the coupling between dynamical and thermodynamical processes is presented. The equations that give the temperature, the excess of radiation and the mean zonal wind for each day of the year are derived. The temperature is given by a second order differential equation that can readily be solved. The zonal wind and the excess of radiation are explicit functions of the temperature.

If in the computations we postulate that the addition of energy by processes other than radiation is a constant, the solution agrees remarkably well with the observed values, except in the months of May, June and July.

It is shown that using only meridional turbulent diffusion transport of heat by large eddies, the required transport is accomplished. The theoretical solution requires a transport with the following exchange coefficients: 5 × 1010 cm2 per sec in February and in March, 4.5 × 1010 in October, 4 × 1010 in January, 3.5 × 1010 in November, 3 × 1010 in September and in December, 2 × 1010 in April, 0.25 × 1010 in August, and zero in May, June and July. There are two maxima of the value of the exchange coefficient: one in February and the other in October. The order of magnitude of the values of the exchange coefficient of our solution is in complete agreement with the value corresponding to the migratory cyclones and anticyclones of the middle latitudes, treated as turbulent eddies, which is equal to 5 × 1010.

The theoretical solution correctly gives the position and strength of the jet stream, except in May, June and July. Therefore we can conclude that, except in these months, the mean daily circulation is mainly a result of the transfer of energy by radiation processes and the turbulent meridional transport of heat by the migratory cyclones and anticyclones.
On the numerical simulation of buoyant convection
Authors: Lilly D. K.
Published: January 2012

The two-dimensional turbulent vortex generated by release of buoyant fluid from an instantaneous thermal line source has been simulated by machine numerical solution of a complete set of Eulerian gas equations. The equations included turbulent eddy exchange tern, similar to those used by Smagorinsky, which made possible the generation of computationally stable solutions qualitatively and quantitatively resembling the convective "thermals" studied and described by Scorer and Richards. The results of a number of numerical experiments, performed with varying computational approximations, lead to conclusions as to the importance of various sources of numerical errors and the validity of the eddy exchange formulation. The formulation leads to qualitatively good results with the resolution provided by about 1600 grid points, but it has not yet been possible to exhibit the shape-preserving stage assumed in theoretical treatments and found approximately by laboratory experiments. This is probably due in large part to the neglect of the effects of eddies in the third dimension.
Structural characteristics of the subtropical jet stream and certain lower-stratospheric wind systems
Authors: Newton Chester W. , Persson Anders V.
Published: January 2012

Analyses of the wind field are presented for several caws, which illustrate the considerable variability in structure of the subtropical jet stream. Two cores of strongest wind are common, one lying in the break between the middle and subtropical tropopause and the other often lying above the subtropical tropopause. The layer of strongest wind on the cyclonic flank slopes upward toward north and is often identifiable as a discrete wind-speed maximum several kilometers above the polar-front jet stream. On the anticyclonic flank, the lower subtropical jet slopes downward toward south and is sometimes stronger than the higher-level layer of maximum wind.

Although the broad-scale structure of the wind fields is qualitatively in accord with the solenoid field, large deviations from the thermal wind relationship are found in layers of restricted depth. Measured vertical shears are often double or triple the size of the thermal shear, and in certain regions the thermal and actual shears are of opposite sign. These deviations are shown to be associated with inertial effects arising from curvature of the flow, and from variations of curvature with height.

An example is given illustrating the shallow filaments of strong wind sometimes found in the lower stratosphere above the tropospheric jet streams. These are not indicated by the thermal field, and are evidence of strong domination by inertial effects.
Breaks in the Indian summer monsoon as a phenomenon of interaction between the easterly and the sub-tropical westerly jet streams
Authors: Ramaswamy C.
Published: January 2012

The present paper contains the results of the study of a synoptic situation over India during a period of 8 days in which normal monsoon conditions were followed by a break and were further followed by a return to normal monsoon. This study has shown that during breaks in the monsoon, a trough in the middle latitude westerlies with a jet embedded in it increases considerably in its amplitude and gets retarded as it moves into the Tibetan Plateau on account of its entering a region of weaker basic current. The large-amplitude trough weakens or destroys completely the Tibetan high at the 500 mb level and appreciably weakens the easterlies at the higher levels to the south of the Himalayas. Protruding into India and Pakistan, the large amplitude trough contributes to the development of heavy rainfall along and near the foot of the Himalayas which is characteristic of the break conditions. The southward protrusion of the trough and its subsequent movement eastward, is also indirectly responsible for a corresponding shift of the high over Iran and Arabia, which, in its turn, seems to lead to the formation of a secondary jet core in the easterlies west of 80° E between 20° N and 25° N. Consequent on the above developments, the westerly jet which had retreated to the north of the Himalayas at the time of the onset of the monsoon reenters the Indo-Pakistan sub-continent during the breaks. Thus we see during break conditions, the remarkable spectacle of two jets of entirely different types-the easterly and the sub-tropical westerly—within a short latitudinal distance of each other and dynamically interacting with each other.

The above detailed study, supplemented by a general examination of the monthly mean 700 mb charts for the northern hemisphere for a period of 10 years, suggests that active monsoon over India is closely associated with high index circulation in middle latitudes over Asia and neighbourhood, while weak monsoon is closely associated with low index circulation over the same region.
Some possible chemical contributions towards the formation of the atmospheric electric charge
Authors: Papée Henry M. , Zawidzki T. W. , Petriconi Gianxa L. , Montefinale Alberto C.
Published: January 2012

Laboratory experiments show that some solid particles which occur in the atmosphere can act as strong electron emitters when irradiated with visible light, while other substances, because of their chemical composition, can assume substantial negative electric charges. Implications resulting from these effects are discussed.
Kinematic and thermal properties of a large-amplitude wave in the westerlies
Authors: Newton C. W. , Palmén E.
Published: January 2012

The characteristics of a large-amplitude long wave, with superimposed short-wave disturbances, are described with emphasis on the deviations between the real and geostrophic winds, and between the corresponding vorticity fields. In the long-wave trough and ridge, the maximum wind speed differed from the geostrophic wind by a factor of about two. Correspondingly large differences were observed between the thermal shear and the vertical shear of the real wind. Consistent with this, the slope of the polar front was much steeper in the trough, and shallower in the ridge, than is indicated by Margules’ formula for straight flow. The vertical shear was also influenced by the change of trajectory curvature with height, which is shown to be systematically related in part to the vertical motion field. The regions of strongest divergence and convergence in the upper troposphere lay very nearly on the jet-stream axis, and local maximum values were an order of magnitude larger than the mean divergence over the region between trough and ridge of the long wave. Kinematically computed vertical motions indicate descent west and ascent east of the trough, in the warm air; in the cold air mass, however, there was ascent west and descent east of the trough line. The differential adiabatic heating or cooling associated with this distribution of vertical motions contributes to strengthening of the horizontal temperature gradient in air approaching the trough, and a weakening in the air streaming eastward from the trough. The indicated redistributions of potential energy are qualitatively in accord with kinetic energy variations along the current, on the west and east sides of the trough where marked deceleration and acceleration are observed in the upper troposphere.
Standardization of natural tritium measurements
Authors: Östlund H. Göte , Brown Robert M. , Bainbridge Arnold E.
Published: January 2012

A series of water samples prepared in Stockholm from tritium-free water and NBS-standard tritiated water have been used to check the accuracy of natural tritium measurements in our three laboratories. There is evidence of pick-up during analysis to the extent of 1-2 TU in one of the laboratories, but otherwise all results from the three laboratories agreed well with the values calculated from preparation of the samples. Agreement waa also obtained on a second series of reference samples prepared and distributed by the International Atomic Energy Agency, Vienna.
Stockholm natural tritium measurements. I
Authors: Östlund Göte , Lundgren Lars B.
Published: January 2012

After a brief description of our methods and standards for the determination of tritium in natural water, results are reported on the controversial rain water samples from Valentia, Ireland. The main part of this paper is a selection of tritium and deuterium data on samples, which may have general geophysical interest. Among them are long series of monthly precipitation from global and Scandinavian networks, and samples from rivers feeding into the Baltic.
Convective instability in a two-layer fluid heated uniformly from above
Authors: Welander Pierre
Published: January 2012

A fluid in which the dynamic and thermodynamic coefficients (μ, α, χ, cp etc.) vary vertically may become unstable when it is heated uniformly from above, assuming that the basic stratification is gravitationally stable and that the thermal expansion coefficient is positive. This “anti-convection” is studied in the special case of a fluid composed by two semi-infinite layers, each of which has constant coefficients. In the theory the Boussinesq approximation is used for each layer separately, and the interface is assumed to be plane. These assumptions seem justified in the present problem.Instability is favoured when the thermal expansion coefficient and the conductivity are large in one of the layers and small in the other layer. A necessary condition for instability is that the ratio μ1 ɑ1Cp2/μ2ɑ2Cp1 is larger than 9 (or smaller than 1/9), where μ is the dynamic viscosity, α the thermal expansion coefficient, and cp the specific heat per unit mass. When this condition is fulfilled instability will occur for sufficiently large values of the ratio Χ1/Χ2 (small values, respectively), where Χ is the thermometric conductivity.The convection cells are confined to a region next to the interface. Small cells have comparable width and height, while larger cells are flattened in proportion to the 1/6 power of the Rayleigh number. Because of counteracting non-linear effects the convective motion cannot grow very large, the vertical velocities can at most be of order Χ/D, where D is the scale of the cell. It is suggested that cells with Rayleigh numbers of order unity dominate the picture in finite amplitude situations.The driving energy comes from a region next to the boundary in the fluid layer having the larger thermal expansion and conductivity. Any motion started in the other layer creates thermal perturbations that are conducted into this region inducing a reversed circulation. When the thermal expansion coefficient is large this reversed circulation becomes strong. Through the frictional coupling it can directly amplify the primary motion and an instability develops.It should be possible to observe the instability in a laboratory experiment. A mercurywater system seems suitable for this purpose. The theoretical analysis shows that instability occurs when heating is applied at temperatures below 18°C.Geophysical and astrophysical applications seem possible. As example, the instability may appear at the interface between the atmosphere and the sea. An air-water system is stable under laboratory conditions, but in nature the existing eddy friction and conduction change the conditions considerably, and such as to favour the occurrence of the instability.
Measurements of ion concentrations in the D-region of the ionosphere with a Gerdien condenser rocket probe
Authors: Pedersen A.
Published: January 2012

This report describes the development of a Gerdien condenser rocket system for measurements of ion concentrations in the ionospheric D-region. The Gerdien condenser and the instrumentation connected to it is separated from the rocket close to the top of the rocket trajectory, and the measurements are done during the descent with the instrumentation hanging under an inflatable parachute. Data from the first launchings at White Sands Missile Range indicate that the concentration of positive ions is of the order of 104 cm−3 and the concentration of negative ions is of the order 103 cm−3 in the height range 50–70 km. This indicates that heavy negative ions, which cannot be collected by the Gerdien condenser, most probably are present in the same height range. Heavy negative ions may be formed in chemical reactions or in clustering processes. Recombination to dust seems to be important below 50 km. This may be due to high dust concentrations above the launch site or dust layers from volcano eruptions observed at the time of the rocket firings.