bluuebunny/crossref_metadata_2025_split huggingface dataset:
The quasi‐geostrophic advective wave in a baroclinic zonal current
Authors: Sutcliffe R. C. 
Published: February 2007

AbstractAn idealised advective wave is studied on the assumption of geostrophic advection of temperature. There is a genuine instability of zonal motion due to this factor and the wave form is similar to thermally asymmetrical depressions and anticyclones. The speed of the unstable waves is Ū − Uc/2 rather than the Ū − Uc of barotropic theory (Ū the mean zonal wind, Uc the Rossby westward component due to variation of Coriolis parameter).Waves become stable when (approximately) the root‐mean‐square zonal thermal wind becomes equal to Uc. This is near the stationary wave length. There are two types of stable waves, the thermally in‐phase and the thermally antiphase waves. The antiphase waves move eastward relative to the surface zonal flow, the in‐phase waves are retrograde.The wave characteristics depend on the thermal‐wind conditions, the surface zonal wind is simply additive to the wave speed.The results support the author's development theory. They do not encourage much optimism in the direct application of barotropic concepts to the baroclinic atmosphere.
Billow clouds
Authors: Scorer R. S. 
Published: February 2007

AbstractThe difficulties of deducing a formula for the dimensions or spacing of cloudlets on the assumption that they are convection cells or unstable waves are discussed. The formula

where h is the depth of the statically unstable layer is then deduced for billow clouds of a particular type, on the assumption that they consist of parallel rows of rotating masses of air moving with the mean wind of a shearing layer and sandwiched between stable wave motions above and below.
A technique for wind analysis and forecasting as applied to Victoria, British Columbia
Authors: McIntyre D. P. 
Published: February 2007

AbstractThrough the use of statistics the most frequent wind directions at Victoria are isolated and their causes considered. Charts of the seasonal variation in wind direction are constructed and the causes for these changes discussed. Finally the data are developed to permit quantitative forecasting of the wind direction at Victoria and the probabilities of the accuracy of the forecasts are calculated.
Condensation nuclei and the development of radiation fog
Authors: Best A. C. 
Published: February 2007

AbstractThe growth of liquid‐water droplets upon condensation nuclei as the relative humidity rises from 80 per cent to 100 per cent is examined. It is assumed that the condensation nuclei consist of sea‐salt particles and that the droplets are always in instantaneous equilibrium with the ambient relative humidity. An arbitrary nucleus‐size distribution formula, which is easily adjusted to fit an intuitively reasonable size distribution, is also assumed. It is found that the shape of the nucleus‐size distribution curve has very little effect upon the computed value of the liquid‐water content W of the fog though at saturation W varies as the square root of the mean mass of the nuclei. In near‐saturation conditions a small variation in relative humidity has a big effect upon W.A formula for drop‐size distribution in fog at saturation is developed and found to agree with measurements.Visibility in the developing fog is briefly considered and it is shown that Koschmieder's formula, applied to the growing water drops, leads to results consistent with experience. Neither the mean nucleus mass nor the shape of the nucleus‐size distribution curve affect the visibility at saturation.
A comparison of hemispheric circulations with particular reference to the western Pacific
Authors: Gibbs W. J. 
Published: February 2007

AbstractUsing daily hemispheric synoptic charts for midwinter and midsummer months the distributions of pressure systems in the two hemispheres are compared. From mean pressure charts and charts of ‘mean streamlines,’ meridional cross‐sections of mean zonal wind have been constructed for the western Pacific for the mid‐months of the four seasons. The main features of the circulation in the Australian region are discussed and comparisons are made between the circulations of the hemispheres.
The conditions for dynamical similarity of motions of a frictionless perfect‐gas atmosphere
Authors: Batchelor G. K. 
Published: February 2007

AbstractThe object of this paper is to show, in an elementary way, the general significance of the Richardson number for motions of a frictionless perfect gas of variable density subject to gravity. Dimensionless parameters like the Richardson number are important in relation to the concept of dynamical similarity of flow fields, and as a consequence the paper consists largely of discussions of the conditions for dynamical similarity of flow fields of specified kind. It is established that if the flow fields are such that the pressure and density everywhere depart by small fractional amounts only from the values for an equivalent atmosphere in adiabatic equilibrium and if the vertical length scale of the velocity distribution is small compared with the scale height of the atmosphere, the Richardson number is the sole parameter governing dynamical similarity. Various possible forms of the Richardson number are examined.
Transverse flow at entrance and exit to jet streams
Authors: Murray R. , Daniels Sylvia M. 
Published: February 2007

AbstractFrom a statistical examination of wind observations near jet streams, two conclusions are reached:(a) In the jet‐stream entrance region there is evidence of a component of wind towards the left (looking downstream), and this reaches a maximum at the level of the jet centre and falls off above and below. It is probable that this arises from an ageostrophic flow across the contours as a consequence of the acceleration of the air downstream. The transverse flow would be consistent with the existence of a direct thermal circulation either above or below the jet stream, or both.(b) In the exit region the cross‐stream wind component is towards the right (looking downstream), and it reaches a maximum at the level of the jet centre and falls off above and below. This probably arises from an ageostrophic motion across the contours as a result of the deceleration of the air downstream. It would be consistent with an indirect thermal circulation either above or below the jet stream, or both.For a sample of observations over the British Isles, the jet axis in entrance regions is in the mean about 2,000 ft (27 mb) higher than in exit regions.
A photoelectric raindrop spectrometer
Authors: Mason B. J. , Ramanadham R. 
Published: February 2007

AbstractAn instrument which gives a continuous, automatic record of the size distribution of raindrops at ground level is described. The light scattered by the drops in falling through an optically defined area of a light beam is focused on to a photomultiplier cell and the resulting voltage pulses are sorted electronically into eight different size groups. The spectrometer is used to study the variation of the drop‐size spectrum with time and with the rate of rainfall. Calibration curves and some specimen results are presented.
The origin of atmospheric nitrous oxide
Authors: Goody R. M. , Walshaw C. D. 
Published: February 2007

AbstractNew observational data are discussed which indicate that:(a) Nitrous oxide is uniformly mixed with the atmosphere up to 10 km and perhaps to 40 km, and that the volume mixing ratio is 3.5 × 10−7.(b) Bacterial reactions in the soil can supply nitrous oxide to the atmosphere at a rate sufficient to compensate photo‐chemical decomposition.(c) The formation of nitrous oxide by homogeneous chemical reactions is probably of less importance.(d) The average magnitude of the nitrogen cycle between earth and atmosphere is probably not less than 1011 molecules cm−7 sec−1..
The nature of convection as revealed by soaring birds and dragonflies
Authors: Scorer R. S. 
Published: February 2007

AbstractBirds and dragonflies can be used as indicators of the extent and intensity of vertical currents, particularly of the nature of convection below cloud base during its period of growth. The bubble theory of Scorer and Ludlam is used to interpret the observations of Hankin in India. The possibility of deriving information from the flight of swallows in Britain is also discussed. In hot sunshine and no wind the air appears to stream steadily upwards from fixed places for the first few metres. The birds indicate that convection develops upwards, the heavier ones which soar at greater heights taking to the air last. The upcurrents are stronger and wider at greater height and drift with the wind; they react more slowly at greater height to changes of sunshine on the ground. When convection is intense the upcurrents appear more sharp‐edged. Puffs of wind are associated with the descent of air from above the superadiabatic layer to replace a part of that layer that is ascending as a newly‐created bubble. When the air is stirred mechanically by wind, bubble formation in the lowest layers is reduced.It is suggested that air movements on the scale of ordinary convection are an element in the climate as important as any other in the life of many birds.
Dimensionless equations for the growth of a drop of salt solution
Authors: Best A. C. 
Published: February 2007

AbstractThe usual equations for the transfer of heat and water vapour to and from a drop of salt solution in an atmosphere with which the drop is not in equilibrium involve the relative humidity of the atmosphere, the drop size, the mass of the salt nucleus and various physical characteristics of air and water which depend upon temperature. Generally an explicit solution of the equations is not possible and, if more than one set of circumstances are to be considered, considerable labour may be involved in obtaining numerical solutions. The following paragraphs indicate a convenient way of manipulating the equations so that the effects of different temperatures and different salt nucleus masses may be allowed for by means of a simple multiplying factor.
The computation of forecast charts by application of the Sawyer‐Bushby two‐parameter model
Authors: Bushby F. H. , Hinds Mavis K. 
Published: February 2007

AbstractTwo series of 12‐hr and 24‐hr forecast 500 mb, 1,000 mb and 1,000–500 mb thickness charts have been computed electronically using the Sawyer‐Bushby (1953) two‐parameter baroclinic model of the atmosphere. The results are compared with the actual charts, and a good degree of correspondence is found between the actual and computed charts.
Solar radiation and the duration of sunshine
Authors: Black J. N. , Bonython C. W. , Prescott J. A. 
Published: February 2007

AbstractRecords of solar radiation (Q) and of duration of sunshine (n) on a monthly basis have been collected for 32 stations and regression equations relating the data calculated in the form Q = QA (a+bn/N) where QA is the maximum possible radiation in the absence of an atmosphere, and N is the maximum possible duration of bright sunshine. For five of these stations records for long series of individual months have been examined and for all stations mean monthly values. In the overall regression equation a = 0.23 and b = 0.48.
Modification of the size distribution of falling raindrops by coalescence
Authors: Mason B. J. , Ramanadham R. 
Published: February 2007

AbstractThe manner in which the size distribution of raindrops is modified during their fall by mutual coalescence, accretion with cloud droplets, and by evaporation below cloud base is investigated. It is shown that if a constant flux of raindrops having an exponetial size distribution occurs at the level of origin (just below the melting level in a layer‐cloud) to give a steady‐state, this initial distribution will undergo considerable modification after a fall of 1 km, the smaller drops being seriously depleted and the larger ones increased. All three processes will cause a shift in the drop‐size spectrum towards larger diameters and produce an increase in the intensity of the radar echo at lower levels of the kind which is sometimes observed. Because of this modification of the drop‐size spectrum during fall and because of the rather rapid fluctuations which are frequently observed in the distribution at the ground, it is not often possible to correlate the latter with the intensity of the radar echo located higher up.
The distribution of wave heights and periods in ocean waves
Authors: Darlington C. R. 
Published: February 2007

AbstractAutomatic records of deep ocean waves obtained by a British Ocean Weather Ship have been analysed. The results are compared with those of similar analyses made by other writers. Relations between the parameters describing wave heights are shown to be in close agreement with deductions made by Longuet‐Higgins from a theoretical model, over a range of wave heights which includes all but the most exceptional conditions. Wave‐period parameters are also calculated, but relationships between them are not so clearcut as for wave heights.
The electric charge of raindrops
Authors: Smith L. G. 
Published: February 2007

AbstractThe observations which are described and discussed in this paper were obtained using equipment designed to record rapidly, and without ambiguity, the electric charge and size of individual raindrops. The electric charge is measured by electrostatic induction on a metal cylinder as the drop falls through. The size of the smaller drops is determined from the time of fall between two such cylinders, while the size of the larger drops is measured by the change of capacity of a parallel‐plate condenser as the drop passes between the plates. The point‐discharge current, electric‐field strength and rain current were also measured.The observations show that on all occasions the range of charge on a particular size of drop is large, often including both signs, and that this range is not appreciably reduced by considering drops recorded during shorter time intervals. However, it is often found that the average charge and the limits of the range of charge show definite relations to the size of the drop. The variation of average charge is such that there is a certain size for which the average charge is zero; for smaller drops the average charge is opposite in sign to that of the electric field, while the larger drops have average charges of the same sign as that of the electric field.On some occasions the charges on the drops are too small to be recorded. The field is then usually reversed to a small negative value. It is suggested that the drops are falling from electrically neutral or slightly electrified clouds, the reversal of the field resulting from the splashing of drops on the ground.The capture of ions by raindrops falling in the region of the point‐discharge current below an electrified cloud is examined and it is shown that, if reasonable assumptions are made about the initial charges on the drops, the relation between the charge and size of drops arriving at the ground is similar to that found experimentally. Comparison of theory and experiment indicates that the field increased with height owing to the point‐discharge space charge.The range of charge is attributed to the mixing, while falling, of drops leaving the cloud base in regions of different current density. This requires that the regions of high current density are small areas of the cloud base, probably not exceeding 100 m in diameter.
The influence of variable mixing ratio and temperature on the radiation flux
Authors: Plass G. N. , Fivel D. I. 
Published: February 2007

AbstractA rapidly convergent solution is obtained for the equations of radiative transfer. An absorbing atmosphere having an arbitrary variation of mixing ratio, temperature and pressure with height is considered. The Lorentz shape of the spectral lines together with the dependence of their line strengths and half‐widths on pressure and temperature are taken into account in the calculations. It is assumed that the lines do not overlap and the range of validity of this approximation is stated. It is shown that the expression for the absorption of radiation over a path between any two heights can be written in a tractable form even after three‐fold integration over the variable conditions along the path, over frequency and over all angles in the hemisphere. When the mass per unit area, along the path, is small or the line intensity is small or both, thus causing the absorption of radiation to be small even at the centre of the line, the integrated absorption is proportional to the dimensionless constant gamma that occurs in atmospheric radiation problems; when these quantities are large, thus causing the absorption to be complete for several half‐widths from the centre of the line, the integrated absorption is proportional to the square‐root of gamma. This is the generalization to variable path conditions of the linear and square‐root relations of infra‐red spectroscopy. Some examples of the method developed here are given when the variable conditions along the atmospheric path can be represented with sufficient accuracy as polynomials. An approximation to the H2O and CO2 distributions shows that the absorption of radiation from the ground at a given height depends greatly on the variation of the mixing ratio with height.
The possibilities of multilayer coatings for auroral research
Authors: Jarrett A. H. 
Published: February 2007

AbstractAlthough the examination of the spectra of aurorae provides a method of estimating temperature at auroral levels, the low dispersion of auroral spectrographs hitherto used and the long exposures required lead to uncertain results.During the past five years it has been established that multilayer coatings are generally more efficient than their silver counterparts for interferometric work. This increase in efficiency is effected by a reduction in the absorption from, for example, 3 per cent for a silver film of 94 per cent reflectivity to 1 per cent for a multilayer coating reflecting 94 per cent of the incident light. Consequently the transparency of a Fabry‐Perot interferometer can be considerably increased by the use of multilayer coatings, so reducing the exposure‐time for recording fringes from an extended source.Several trials on auroral glows have shown that it is possible to record Fabry‐Perot fringes from the 5577 Å radiation with exposures of as little as 20‐min duration, using simply a multilayer interferometer placed in front of an f/2 camera.These investigations are being continued with the intention of deriving temperature distributions from measurements of the fringe halfwidths, and line‐of‐sight motions of the aurorae from displacements of the fringes.Further applications lie in the use of narrow bandwidth (≃ 20 Å at 5500 Å and 60 per cent transmission) all‐dielectric type interference‐filters, particularly for investigating the form of a display in different radiations (e.g. Hα, Hβ); these filters by relative enhancement of the auroral radiation will make observations possible during moonlight.
Gust variation with height up to 150 m
Authors: Deacon E. L. 
Published: February 2007

AbstractMeasurements, on occasions of strong wind, of horizontal wind gusts at heights of 12, 64 and 153 m in open country show the increase of gust speeds with height to be markedly less than that of mean wind speed. Lack of synchronism between gusts at the various heights makes it necessary, for wind‐pressure applications, to examine the maximum values of wind speed averaged over the three heights. At the times of occurrence of these maxima, the wind speed is approximately proportional to the height raised to the power 0·085. The corresponding index for the mean speed is 0·16.Some results on the structure of turbulence are applied to enable predictions of extreme vertical gust velocities to be made.
The Ekman spiral
Authors: Ellison T. H. 
Published: February 2007

AbstractPrevious workers have used an eddy viscosity varying with height linearly or according to a power law, when discussing the variation of the wind between the surface and the height at which it (supposedly) attains the geostrophic value, but they have not used the appropriate boundary conditions to obtain the familiar forms for the velocity profile very near the surface. In conditions of neutral stability this profile is given by

where u* = (τ)1/2 and k = 0·40. Eq. (1) corresponds to an eddy viscosity, KM, given by

If this formula is assumed to hold at all heights, and the geostrophic wind is assumed to be uniform and constant, it can be shown that

where u is the component of the wind in the direction of the surface wind and v that perpendicular to it; the suffix G denotes the geostrophic value and f is the Coriolis parameter.
Water‐vapour flux and flux‐divergence over Southern England: Summer 1954
Authors: Hutchings J. W. 
Published: February 2007

AbstractAverage zonal (eastward) and meridional (northward) transfers of water vapour for the period June‐August 1954 are computed at four aerological stations in southern England ‐ Liverpool, Hemsby, Crawley and Camborne‐at levels corresponding to the earth's surface, 950, 900, 850, 800, 750, 650, 550, 450, and 350 mb.In the zonal direction average transfers are eastwards and reach a maximum of 400–500 g (cm 100 mb sec)−1 below 900 mb. In the meridional direction both northward and southward transfers occur and their vertical distribution varies from station to station. Largest meridional transfers are of the order of 100 g (cm 100 mb sec)−1 and normally occur below 800 mb. Both zonal and meridional transfers become small near 350 mb. Vertically integrated eastward and northward transfers are respectively: Liverpool 1461, ‐13; Hemsby 1541, 226; Crawley 1701, 132; Camborne 1781, ‐42 g (cm sec)−1..Average zonal eddy‐transfers are normally eastward and amount to only a small percentage of the total zonal transfer. Average meridional eddy‐transfers are northward, amount to a large percentage of the total meridional transfer and in some cases are oppositely directed. Vertically integrated eastward and northward eddy‐transfers are respectively: Liverpool 63, 73; Hemsby 81, 58; Crawley 97, 27; Camborne 113, 125 g (cm sec)−1. Although directed roughly from high to low values of average specific humidity, average eddy‐transfer vectors at a given (geometric or pressure) level bear little quantitative relation to average (horizontal or isobaric) specific humidity gradients at the same level.Assuming the above transfers to vary linearly between stations, computation of the net horizontal outflow of water vapour from the region shows marked convergence of water vapour from the surface to 850 mb with divergence above this. For the three months' period this amounts to a net inflow of 31 g cm−2 at low levels and a net outflow of 23 g cm−2 at higher levels. Increase in storage amounts to approximately 1 g cm−2, thus leaving a surplus of precipitation over evaporation of approximately 7 g cm−2. Estimation of precipitation from isohyetal charts and evapotranspiration by empirical methods yields a corresponding surplus of 6 g cm−2..Computation of the large‐scale vertical transfer of water vapour (using instantaneous kinematically‐computed vertical velocities) at 900, 800, 700 and 600 mb showed that at these levels large‐scale vertical eddy‐transfer of water vapour is negligibly small. Using mean vertical velocities and specific humidity averaged over the area at 950, 850, 750, 650, 550 and 450 mb, computations yield large‐scale upward transfers of water vapour for the three months' period amounting to 17, 23, 13, 6, 2, 0 g cm−2 respectively at the above levels. This flux is shown to be inadequate for water‐balance requirements and it is concluded that a considerable part of the upward transfer is carried by turbulent and convective systems of essentially smaller scales.