bluuebunny/crossref_metadata_2025_split huggingface dataset:
The wave patterns produced by a moving body in a compressible, density‐stratified fluid
Authors: Rarity B. S. H. , Hide R. 
Published: February 2007

AbstractThe two‐dimensional wave field generated by a steadily moving source in a stratified compressible medium is determined. The dispersive character of the waves gives rise to wave crests of an asymmetrical form, present in some parts of the plane and forbidden in others. It is shown how the location, direction of motion and the length scale of the source can be estimated from the observed wave field, acknowledging that such information will usually be fragmentary.
Global meridional interactions in stratosphere and troposphere
Authors: Pittock A. B. 
Published: February 2007

AbstractSignificant correlations have been found between year to year mean latitudes of the surface high pressure belt, L, over eastern Australia and atmospheric parameters such as total ozone, winds and temperatures at various levels in the troposphere and stratosphere, and rainfall. In those years when, in late winter and spring, the high pressure belt lies nearer to the Equator it appears that the Hadley circulation and poleward transport processes in the lower stratosphere and upper troposphere in middle latitudes are stronger. This is probably also associated with the earlier breakdown of the winter stratospheric polar vortex.Evidence is presented to support the view that L is determined to a good approximation by the criterion for baroclinic instability which was derived by Phillips and Smagorinsky and applied to climatology by Flohn and Henning. Thus variations in L are related to variations in the driving force of the Hadley circulation, which in turn may well be related to variations in sea surface temperature. This encourages the view that an empirical and theoretical basis for long‐range seasonal forecasts of temperate zone climate may be in prospect. The results should lead to a greater understanding of the nature of global climatic change.
Hurricane Agnes — an event shaped by large‐scale air‐sea systems generated during antecedent months
Authors: Namias J. 
Published: February 2007

AbstractAn attempt is made to show that the life history of hurricane Agnes was determined by the antecedent slow evolution of the general circulation on a time scale of months. A self‐aggravating complex of midtropospheric anomalies is described and quantified ‐ this complex predisposing the eastern seaboard to the aberrant path assumed by Agnes and providing deep moisture‐laden air masses from a very warm western Atlantic. The stable configuration of the centres of action is partly attributed to ocean‐atmosphere interactions.
Vertical velocities and vertical eddy fluxes derived from serial soundings at one station
Authors: Tucker G. B. 
Published: February 2007

AbstractDetailed 3‐hourly soundings of the atmosphere from 0–30 km for one month (September/October 1967) over Laverton, Victoria (38°S) are analysed to obtain vertical velocities using the heat balance method. Results are assessed to be reliable from the point of view of error estimates, synoptic compatibility and statistical features for the whole month. The tendency for a reversal of vertical velocity between low and high troposphere occurs, with occasional very strong downward velocities (∼ 30 cm s−1) at the tropopause level. Convergence of vertical eddy flux of both momentum and sensible heat is shown to occur near the levels of maximum poleward eddy transport with magnitudes equivalent to 1 · 5°K/day and 3 m s−1/day. Similar computations based on routinely available upper‐air soundings at standard pressure levels at 12‐hourly intervals are shown to give quite different (spurious) results. As a supplementary result, strong horizontal eddy transports are revealed in the middle stratosphere.
Meso‐scale circulations and rainfall patterns in an occluding depression
Authors: Atkinson B. W. , Smithson P. A. 
Published: February 2007

AbstractSynoptic and meso‐scale precipitation and airflow patterns in the occluding depression which passed over England and Wales on 8‐9 March 1967 are analysed. Large‐scale circulations are illustrated in terms of airflow relative to the synoptic system within the framework of surfaces of constant wet‐bulb potential temperature (θw). Meso‐scale precipitation and airflow configurations are inferred from a sequence of over 120 large‐scale maps of 13‐min precipitation amounts. There was no obvious ‘conveyor belt’ in the occluding depression, but the upward relative flow coincided closely with large rain areas of the warm front and the depression centre. Subsidence at the cold front and within the warm sector inhibited precipitation growth in those parts of the depression.Large (200 times; 50 km) and small (50 times; 50 km) meso‐scale rain areas were found in the depression. The latter resulted from clusters of generator cells, which formed in an area where potential instability was released by large‐scale upward motion. The clusters moved with the winds at about 550 mb. The large meso‐scale rain area lay at a small angle to the surface warm front and lasted for about three hours. Its size, location, and orientation were due to the movements of three small meso‐scale systems within the relative flow at their generator level. The location and intensity of a small meso‐scale rain area on the eastern flanks of the Pennines, together with the associated rainshadow to the west of the upland, were analysed with the aid of a modified lee‐wave equation. Other small meso‐scale precipitation areas were due to airflow over sub‐synoptic deformations in the θw surfaces. All types fit into a two‐tier scaling of meso‐scale circulations in frontal zones.
Updating prediction models by dynamical relaxation: an examination of the technique
Authors: Davies H. C. , Turner R. E. 
Published: February 2007

AbstractA study is undertaken of a particular method of updating numerical prediction models. the method constrains the time development of a subset of the model fields toward a prescribed space‐time estimate of those fields, while the other model variables are allowed to evolve in an explicitly unconstrained fashion. It represents an attempt to update the model by a form of dynamical relaxation.An analysis of the method is carried out in the context of the primitive equations linearized about an isothermal basic state of no motion. It is shown that, for a particular form of the scheme and the availability of the time history of the mass field (or the wind field) on an f‐plane, all the time‐ and space‐scale error fields in the initial specification suffer an amplitude reduction of at least the order e−1 on the timescale of one day. On an equatorial β‐plane it is shown that the same rate of amplitude reduction can be achieved if an accurate time history is known for both the mass field and the zonal‐wind field. Numerical experiments performed with the nonlinear shallow‐water equations for a mid‐latitude β‐plane geometry support these results and demonstrate that the technique compares favourably with the conventional direct insertion update method. Consideration is also given to the possible effects of errors in the prescribed fields and it is shown that the relaxation scheme can to some extent be tuned to offset the effect of this particular source of error.This study of the relaxation update scheme, although not comprehensive, is nevertheless sufficient to indicate its potential. However, it is stressed that a trenchant assessment of the scheme's usefulness should be based at least in part upon its performance under more testing and realistic conditions.
Orographic rainfall in warm sectors of depressions
Authors: Bader M. J. , Roach W. T. 
Published: February 2007

AbstractResults of some calculations are presented which show that the washout of droplets in a low‐level, orographically produced cloud by raindrops falling from a higher‐level cloud (formed by large‐scale ascent) can augment the rainfall rate by several mm h−1 over a hill a few hundred metres high. The dependence of this enhancement upon different meteorological parameters is discussed and calculated values are compared with some observed rainfall rates over south Wales. It is considered that this mechanism is most effective in enhancing warm‐sector precipitation over hills.
Angular momentum advection by axisymmetric motions
Authors: Plumb R. A. 
Published: February 2007

AbstractIt has been shown by Starr that net absolute angular momentum cannot be advected by axisymmetric motions alone across a closed surface of constant absolute angular momentum. Hence it has been claimed that certain systems possessing differential rotation about a central axis must be non‐axisymmetric. The theorem is analysed in detail and such a conclusion is shown to be invalid.
On the choice of radial boundary conditions for numerical models of sub‐synoptic vortex flows in the atmosphere, with application to dust devils
Authors: Leslie L. M. , Smith R. K. 
Published: February 2007

AbstractThis paper is a sequel to the recent numerical study of thermally driven vortices by the authors. the model developed earlier is used as a basis for comparing a variety of radial boundary conditions and to assess their suitability for models of ‘tall‐thin’ atmospheric vortices, in particular dust devils. We have also determined those aspects of vortex dynamics which are least sensitive to the choice of radial boundary condition, and those which have a stronger dependence. the results confirm the suitability of the boundary conditions used in the earlier study, for the purposes for which that study was intended, but more realistic boundary conditions are obtained for a dust devil model.The discussion should provide useful guidance in the design of future observational studies of dust devils and their immediate environment, and in the formulation of models for other types of sub‐synoptic‐scale vortices such as tornadoes and waterspouts.
Relative role of atmosphere and ocean in the global heat budget: Tropical atlantic and eastern Pacific
Authors: Hastenrath Stefan 
Published: February 2007

AbstractCalculations of the oceanic heat budget for the tropical Atlantic and eastern Pacific, in conjunction with satellite measurements of net radiation at the top of the atmosphere, permit a partitioning of heat export performed by the oceanic water body v. the atmospheric column. For individual Marsden squares, the divergence of heat transport within the oceanic water body ranges from +82% (export) to −120% (import) of the net radiative input to the system at the top of the atmosphere. Oceanic heat export is particularly conspicuous in the realm of the cold currents off the west coasts and in the cold water tongue immediately to the south of the equator.
On air‐borne transport of sulphur over the North Atlantic
Authors: Nyberg Alf , Mason B. J. 
Published: February 2007

AbstractThe sulphur content in the precipitation collected on Ocean weather ships in the North Atlantic has been analysed. From these data and from the results of trajectory computations it is concluded that considerable amounts of anthropogenic sulphur are transported from North America towards Europe. the dry deposition of sulphur over the Atlantic must be small except close to the emitting sources. the amount of sulphur in precipitation from air coming from the high pressure area near the Azores is very small. It is concluded that the normal global value of natural sulphur in precipitation can hardly be larger than 0.1 mg 1−1.
A field study on the representativeness of turbulent fluxes of heat and water vapour at various sites in southern England
Authors: Wood N. L. H. 
Published: February 2007

AbstractExtensive measurements were made of surface flux densities of sensible and latent heat from short grass in unstable conditions using the combined Bowen ratio and surface energy balance method. Simultaneous measurements were taken during anticyclonic periods at sites in southern England, and these were examined for differences due to different environments. Differences were not evident within the accuracy of measurement, although one of the sites (Harlington), being noticeably drier, gave anomalous fluxes during the summer of 1975. Sites with separation on the 10km scale, and later, on approximately the 100km scale, revealed no evidence that mesoscale organization of the convection affects the fluxes of heat and water vapour from the surface. Finally, this paper presents a comparison between energy fluxes determined by the Bowen ratio method at one site and the average flux estimated from a boundary‐layer heat budget study for a large area which included the site.
The nocturnal jet
Authors: Thorpe Alan J. , Guymer Trevor H. 
Published: February 2007

AbstractThree case studies of the nocturnal jet at dawn are presented. Observations were made over southern England where the terrain is considerably less homogeneous than that over which previous published data concerning the jet have been obtained, for example the Great Plains and Wangara.It is shown that previously suggested layer models of the boundary layer can be usefully quantified to give the diurnal evolution of a layer‐average wind. This model, which involves a decoupling of the flow in middle levels from surface constraints by thermal stratification at night, exhibits a nocturnal jet. Two surface‐stress parameterizations, which make the stress proportional to the velocity and to the velocity squared, give a similar wind evolution.The observed abrupt transition in boundary layer structure soon after sunrise is studied by considering the growth and transfer characteristics of perturbations to a homogeneous Boussinesq fluid, which is stratified and possesses an idealized jet wind structure. Depending on the value of an average Richardson number, Ri, two regimes of dynamically unstable eddies are indicated. When +0.35 ≳ Ri −0.03 the preferred eddies are oriented transverse to the shear and when Ri ≲−0.03 they are oriented parallel to the shear. the latter regime, associated with longitudinal convective circulations, is efficient at smoothing the jet momentum distribution to give the characteristic well‐mixed daytime wind profile.
A numerical study of the initiation and early development of convection in temperate atmospheres
Authors: Bennetts D. A. , Roach W. T. 
Published: February 2007

AbstractA recent three‐dimensional numerical model of a tropical cumulonimbus cloud by Miller and Pearce has been adapted to temperate latitudes and it has been found that the mode of development is substantially altered. the tropical cloud has a fairly smooth development whereas the temperate‐latitude cloud is built up by successive thermals. Several integrations have been run and three particularly interesting cases are presented.
On the spectral scale of wind fluctuations within and above the surface layer
Authors: Wamser C. , Moller H. , Panofsky H. A. 
Published: February 2007

AbstractThe spectral scales of the longitudinal and vertical velocity components are investigated by tower measurements up to a height of 250 m at sites of different roughness features. the results are compared with those from the 1968 Kansas experiments. It is shown that the local Monin‐Obukhov parameter z/L at 50 m sufficiently describes the stability dependence of the spectral scales also at greater heights. the influence of roughness on the w scale is investigated qualitatively by classifying the comprehensive data according to stability, height and roughness.
Relations between surface fluxes and mean profiles of velocity, temperature and concentration, downwind of a change in surface roughness
Authors: Mulhearn P. J. 
Published: February 2007

AbstractChanges in surface fluxes (of momentum, heat, and mass) downwind of a surface roughness change, are related to changes in mean profiles (of velocity, temperature, and concentration). the theory assumes that changes in mean quantities are self‐preserving. At fetches sufficiently large for the underlying surface to be specified by an aerodynamic surface roughness, the changes in surface fluxes are related to changes in this quantity. the theoretical results are supported by available experimental data.
The aerodynamics of oblate hailstones
Authors: Thwaites S. , Carras J. N. , McKlin W. C. 
Published: February 2007

AbstractArtifical hailstones having shapes and structures closely resembling natural oblate hailstones have been grown in a vertical icing tunnel. These hailstones were grown by spinning them about the minor axis and at the same time causing the minor axis to move in a conical manner about the horizontal, a motion termed symmetric gyration. It is inferred that natural oblate hailstones undergo essentially this type of motion during growth. the oblateness of the hailstones is determined by the angle of the cone and the observed oblateness of natural hailstones indicates that the most common half‐angles of the cone lie in the range 20° to 45°. the lobes in the hailstones grow in the local direction of impingement of the accreted droplets and this produces characteristic non‐radial divergent lobes along the minor axis.
Baroclinic instability on a sphere in two‐layer models
Authors: Baines P. G. , Frederiksen J. S. 
Published: February 2007

AbstractThe baroclinic instability problem is studied for various two‐layer zonal velocity profiles on a sphere for both quasi‐geostrophic (P) and modified‐geostrophic (L) models, the latter containing nongeostrophic advection of temperature. Critical amplitudes for instability and other properties for the rigid rotation profile are obtained for a wide range of values of the static stability, and results of previous studies on the sphere are related and shown to be mutually consistent. Critical amplitudes are also obtained for some jet profiles, and unstable midlatitude jet profiles with values of the static stability and shear representative of the atmosphere are studied in detail. In particular it is found for the latter that heat fluxes (in the L model) are larger in the lower layer than in the upper, and that their equatorward components (at high and low latitudes) are small; also, there are no growing modes with large equatorial flows as found for the rigid rotation profile. A simple hypothesis which relates the pattern of momentum fluxes to the β‐plane stability criterion, and is consistent with all known results, is proposed.The results, particularly growth rates and stream functions, are compared with those of simplified and multilevel models. For the most unstable mode the differences between the two‐layer and multilevel results are not as large as might be expected on the basis of previous studies, and reasons for this are stated.
Some relationships between sea surface temperature anomalies and surface pressure anomalies
Authors: Haworth C. 
Published: February 2007

AbstractPossible relationships between sea surface temperature anomalies in the tropical east Atlantic and surface pressure anomalies in the Atlantic‐European sector are investigated. From principal component analysis of the sea surface temperature time series in conjunction with the mean surface pressure anomaly distribution, it is deduced that there is a long‐term change in tropical sea surface temperatures associated with variations in westerly component in higher latitudes. Variations of sea surface temperature are shown to be related, through spatial surface pressure eigenvectors, to the surface pressure distribution in most months of the year. Indications are that the atmosphere initially drives the ocean and that the two media subsequently vary in phase. A method of making quantitative forecasts of the sea surface temperature effect on surface pressure is suggested with special reference to the winter season.
The response of North Atlantic sea surface temperature to atmospheric forcing processes
Authors: Daly A. W. 
Published: February 2007

AbstractA depth‐integrated heat energy conservation equation is used with input data from three case studies of dissimilar meteorological forcing to provide values for the month‐to‐month change of mean monthly sea surface temperature anomalies. Evaluation of the model is made by comparison of predicted anomaly changes with those observed. The separate contributions of anomalous surface cooling and anomalous advection to the sea temperature anomaly change, give agreement of varying closeness: in all three studies best results are achieved by a combination of these processes; in each case inclusion of a horizontal diffusivity term produces deteriorations over sea temperature anomaly changes based on a combination of anomalous heat loss and advection terms. In regions of significant anomalous windstress curl, neither sea temperature anomaly changes produced in part by advection due to an alternative meridionally directed flow, nor changes otherwise consequent on the associated effects of induced vertical motion, are observed to be consistent with actual changes.
Maintenance of kinetic energy in large‐scale tropical disturbances over the eastern Atlantic
Authors: Kung E. C. , Burgdorf H. A. 
Published: February 2007

AbstractWith the GATE upper air data an A‐B scale area and a B scale area are defined over the eastern Atlantic for the energetics analysis of tropical disturbances in the space domain. Computed gross energy budgets at A‐B scale for large‐scale disturbances and at B scale for cloud cluster scale disturbances clearly indicate that these possess distinctly different energetics regimes in and above the mid troposphere.It is shown that the eddy available potential energy is added to its tropical reservoir at B scale. However, at A‐B scale the eddy available potential energy is released as the source of kinetic energy. The released energy in large‐scale disturbances appears as eddy kinetic energy in the upper layer above 200mb, and cascades to smaller scales. Examination of the residual term of the eddy kinetic energy equation with other terms also indicates that A‐B and B scale disturbances significantly interact with other scales.
Airborne studies of electric fields and the charge and size of precipitation elements in thunderstorms
Authors: Gaskell W. , Illingworth A. J. , Latham J. , Moore C. B. 
Published: February 2007

AbstractDuring the summer of 1976 the ONR/NMIMT research aeroplane was employed in studies of the electrical properties of thunderstorms. Flights through clouds were made in Florida, as part of the Thunderstorm Research International Project, and in New Mexico. The most important measurements were of electric field and the charge, Q, and size, d, of individual precipitation elements. A novel device was constructed for the Q and d measurements. The charge carried on a particle passing through a metal cylinder was sensed by induction, and its size by a shadowgraph technique involving a linear array of photo‐diodes. The penetrations were generally through the lower regions of the clouds.The major findings of the studies in New Mexico were as follows:
Volume charge densities on precipitation, pp, were often around ‐ 5nCm −3 over horizontal distances of several kilometres. pP was almost always negative, but positive charge densities, of lower magnitude, were occasionally observed over shorter distances. The major contribution to the measured values of pP was made by particles of size around 1 mm, or smaller.
Simultaneous measurements of Q and d showed that no simple relationship existed between them. Charges of about 100pC were commonly observed on particles around 1 mm in size. These are much too high to be explicable in terms of the inductive theory.
Positive and negative charges were found to coexist, except when the precipitation rate, p, was very low. However, charge of one sign (almost invariably negative) was always strongly dominant.
Values of p could be estimated crudely from the d pulses. In regions of high pP they were rarely in excess of 10mmh−1; on some occasios when pP was substantial p was below 1 mmh−1.
Our primary conclusions are that in the clouds studied substantial currents were often carried on precipitation, and that the charges on individual precipitation elements are not explicable in terms of the inductive mechanism of thunderstorm electrification.