bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the dynamics of the general circulation
Authors: Fleagle Robert G. 
Published: February 2007

AbstractThe dominant features of large‐scale atmospheric motion emerge from a relatively simple treatment of the hydrodynamic equations, thus providing clear, intuitive understanding of the relation between cause and effect in the general circulation. The analysis is made possible by applying the perturbation equations to a sloping stream surface located in the middle troposphere. For reasonable values of the arbitrary parameters, the results show that baroclinic disturbances are unstable poleward of a critical latitude, roughly 35°, and that the preferred number of such unstable disturbances at any one time decreases from about 10 at 45°, to 2 at 80°. Greatest intensity occurs at about 60°. Jet streams must form close to the critical latitude and, in the case of long disturbances, at higher latitudes. Anticyclonic shear has a stabilizing influence, so that the normal velocity distribution in middle latitudes offers considerable resistance to penetration of disturbances to low latitudes. Below the critical latitude unstable disturbances are possible only in relatively small areas where the hydrostatic stability is nearly zero. Growth of these disturbances is favoured by anticyclonic shear, as well as by baroclinicity and by high latitude. Disturbances of maximum rate of growth are practically non‐dispersive so that their growth depends mostly on available potential energy. If sufficient energy is available, the identity of individual disturbances can be maintained over extended time periods. Wave speed relative to the zonal current exhibits a maximum positive value at a high latitude.
Anisotropic high‐level turbulence
Authors: Clodman J. 
Published: February 2007

AbstractA study is made of several cases of high‐level turbulence in which the intensity varied with the direction of flight of the aircraft. The direction of maximum turbulence is found to coincide fairly well with the direction of the contour lines. A theory is developed which attributes this type of turbulence to quasi‐horizontal gusts associated with strong horizontal wind shear. Gravity waves are examined as a possible alternative explanation and tentatively rejected.
Preliminary discharge processes in lightning flashes to ground
Authors: Clarence N. D. , Malan D. J. 
Published: February 2007

AbstractBy using different techniques of recording the electrical effects of lightning discharges occurring at varying distances, it has been possible to sort out the major components of pre‐return stroke field changes. A comparison between these field changes has shown that the first return stroke of a lightning flash to ground is usually preceded by three successive and distinct discharge processes.The first, or breakdown stage, is identified from the reversal of its field change with distance as a discharge between the main negative charge centre and the positive charge centre near the base of the cloud at heights of 3.6 and 1.4 km respectively, the discharge probably just as often starting from the positive as from the negative centre. This is followed by the second stage during which the highly conducting channel then existing in the cloud is being negatively charged. The charging continues until the field in front of the channel has become sufficiently strong to propagate a downward‐moving stepped leader breakdown streamer.Stepped leaders have been observed to precede more than 75 per cent of all flashes to ground, though the radiation fields of most stepped leaders are so small that they can only be detected by using very high amplification.The probable mechanisms involved in the preliminary stages are discussed.
Some further observations from aircraft of frost point and temperature up to 50,000 ft
Authors: Helliwell N. C. , Mackenzie J. K. , Kerley M. J. 
Published: February 2007

AbstractDuring 1955, 46 measurements of frost point and temperature were made at varying altitudes up to about 50,000 ft using a Dobson‐Brewer pressurized frost‐point hygrometer and a flat‐plate thermometer mounted on the Canberra aircraft of the Meteorological Research Flight. The general character of these ascents in the lower stratosphere confirms the conclusions of earlier papers (Murgatroyd, Goldsmith and Hollings 1955). The mean frost point at 48,000 ft for the ascents made in 1954 and 1955 is ‐117°F and at 46,000 ft ‐115°F, with a standard deviation of about 3°F in each case.
On a distribution of weather cycles by length
Authors: Gabriel K. R. , Neumann J. 
Published: February 2007

AbstractIn the paper a weather cycle is defined as the combination of a wet (dry) spell with the successive dry (wet) spell. On the assumption that the lengths of wet and dry spells are independent and obey geometric distributions, the distribution function of the lengths of weather cycles is deduced and tested against observational data for Tel Aviv. The peak frequency of weather‐cycle lengths at Tel Aviv is found to be at about 4 days.
The travel and diffusion of the radioactive material emitted during the Windscale accident
Authors: Crabtree J. 
Published: February 2007

AbstractThe reactor accident at Windscale on 10‐11 October 1957 resulted in the release of radioactive fission products into the atmosphere over a period of several hours. Measurements were made of the fission products, particularly iodine‐131, collected on filters exposed for the study of atmospheric pollution in many places in the United Kingdom and Europe: measurements were also made of the iodine‐131 deposited on grass. These showed that the effluent had been widely dispersed, but that activities over England were about an order of magnitude greater than those found over the neighbouring areas of the continent. Meteorological trajectory analysis showed that the main portion of the cloud had remained over England until 15 October, and that the activities over continental Europe were due to the eastern edge of the cloud.Meteorological data were used together with the air concentration data to deduce that about 22,000 curies of iodine‐131 were present in the cloud as it passed over south Lancashire and Yorkshire.
Synoptic and dynamic aspects of climatic change
Authors: Kraus E. B. 
Published: February 2007

AbstractThe changing pattern of world climate during the last hundred years is compared with the inferred pattern of the Pleistocene. Relatively cool climates at high latitudes appear to have been associated much of the time with reduced tropical sea‐surface temperatures, a lower snow‐line on tropical mountains, reduced aridity on the desert fringes and increased storm activity along continental east coasts in middle latitudes. Relatively warm climates at high latitudes tend to be associated with the opposite complex of conditions.Considerations of the water balance suggest that a small temperature decrease would be necessary and sufficient for the re‐establishment of glacial conditions in many regions. Increased snowfall would help but is not essential. Synoptic considerations indicate that glaciation was associated necessarily with strong upper westerlies at relatively low latitudes over the continents and probably with vigorous anticyclones over the subtropical oceans.An increased infra‐red cooling rate in the upper air, particularly over the tropics, could produce all the necessary conditions for the establishment of a glacial/pluvial phase. Possible causes for changes in the infra‐red cooling rate are discussed.
Observations of precipitation elements in cumulus clouds
Authors: Murgatroyd R. J. , Garrod M. P. 
Published: February 2007

AbstractCloud particles of diameters greater than about 100 μ can be sampled from an aircraft by exposing within the cloud a thin aluminium‐foil surface to the airstream and counting and sizing the indentations made on it. A series of flights has been made through cumulus clouds using this technique with the object of obtaining data on the concentrations of these larger particles in clouds of different size and temperature. A series of observations showing the measured concentrations is presented and discussed. Concentrations range from less than 1/m3 in the smaller cumulus clouds up to 1/litre or more in clouds about 1 km thick.
The flux of water vapour due to the mean winds and the convergence of this flux over the Northern Hemisphere in January and July
Authors: Bannon J. K. , Matthewman A. G. , Murray R. 
Published: February 2007

AbstractCharts are presented showing the flux of water vapour due to the mean winds, based on the mean distribution of water vapour and the mean geostrophic winds, in January and July, over an area comprising most of the Northern Hemisphere.There is evidence that this flux approximates fairly well to the total flux of water vapour, but the divergence of this flux does not always approximate so well to the divergence of the total flux. Nevertheless, comparison with independent estimates of evaporation minus precipitation over the oceans suggests that the two divergences are at least of the same order of magnitude, and further comparison with published charts of the divergence of the total annual flux of water vapour suggests some degree of detailed correspondence.
Statistics of lateral gustiness at 16 m above ground
Authors: Smith F. B. , Abbott P. F. 
Published: February 2007

AbstractThe horizontal lateral wind‐fluctuations at 16 metres above ground have been recorded over periods totalling 1,350 hours by a system described by Jones and Pasquill (1959). Hourly‐average values ⊝τ of the standard deviation of wind fluctuations sampled within times τ = 5, 30, and 180 sec are classified according to wind speed and stability s = ΔT/U2 °F/(m/sec)2 (where ΔT is the temperature difference between 7.1 m and 1·2 m, U is the wind speed at 15.5 m). A critical value of stability s = + 0·017 is indicated separating near‐neutral or unstable stabilities (s > 0·017), for which ⊝τ depends primarily on stability, from very stable conditions (s > 0·017), for which wind speed is the dominant parameter. Some support for this transition is also found in the variation of spectrum shape with stability. A second transition on the unstable side may correspond to Priestley's critical value separating forced‐ and free‐convection regimes.The results are in a form suitable for application to particle diffusion in the atmosphere. However, the large variations in wind direction in very stable conditions with light winds cannot be interpreted, at present, in terms of diffusion with the same degree of certainty as in near‐neutral stabilities.
The introduction of topographic and frictional effects in a baroclinic model
Authors: Graystone P. 
Published: February 2007

AbstractThe effects of large‐scale topography and surface friction on short‐range numerical forecasts are investigated using a baroclinic two‐parameter prediction model, modified to include forced vertical velocities. Trial forecasts showed that the damping effect of surface friction is reproducible, but only moderate success was achieved in accounting for orographic influences.
Intensities and spectra of vertical wind fluctuations at heights between 100 and 500 ft in neutral and unstable conditions
Authors: Thompson N. 
Published: February 2007

AbstractRecords of vertical gustiness have been obtained using a sensitive vane attached to the cable of a captive balloon. Electrical filtering of the output signal from the vane reduced the labour of subsequent computation. Intensities of turbulence were found to decrease with increasing wind speed. Length scales generally showed no regular trend with height below 400 ft, because of (a) the dependence of scale on stability, and (b) the heterogeneity of the present data as regards stability. Most spectra exhibited two major peaks.
Attenuation of solar radiation: A climatological study
Authors: Monteith J. L. 
Published: February 2007

AbstractDaily totals of direct and diffuse radiation transmitted by a cloudless atmosphere are calculated from the absorption and scattering coefficients given by Houghton (1954). Estimates of total (direct plus diffuse) radiation (T1) agree well with extreme maxima recorded at several British stations, but during spells of cloudless summer weather in south‐east England attenuation by aerosol decreases total radiation on average by 10 per cent, and increases the ratio of diffuse to total radiation by about 8 per cent of T1. The ratio of mean monthly radiation at country stations T2 to estimated T1 can be expressed as a function of cloud reflection (ρ), cloud absorption (ϕ), and surface reflection (α); and the values ρ = 0·50, ϕ = 0·16 are consistent with surface and aerial measurements. With α = 0·20, T2/T1 is approximately (1−0·61c) (0·6 < c < 0·9) where c is fractional cloudiness. The diffuse component beneath cloud can be estimated separately. Absorption by man‐made aerosol reaches maxima of 26 per cent at Kew and 30 per cent at Kingsway in January, and varies seasonally with measured smoke. In the country, absorption by pollution is negligible in summer but may reach 5 to 10 per cent in winter. At Kew, absorption by cloud and total back‐scattering (local planetary albedo) are about 9 per cent and 41 per cent of extra‐terrestrial flux respectively, with little seasonal variation.
Cloud nomenclature
Authors: Scorer R. S. 
Published: February 2007

AbstractA very much simplified terminology in which cloud names are related to the physical and dynamical mechanisms producing the clouds is needed for the purposes of communication between cloud physicists, and for the purpose of teaching the subject in a scientific manner.Such a terminology is outlined using a few of the best known Latin terms together with selected English words. There is no major departure from recent practice, but definitions are related to mechanisms, not appearances, and are made more exact.
The adjustment of profiles and eddy fluxes
Authors: Dyer A. J. 
Published: February 2007

AbstractAn assessment is made using simple diffusion theory of the rate of adjustment of profiles and eddy fluxes for (a), the leading‐edge case as a function of distance and (b), the horizontally uniform case as a function of time. The solutions of the appropriate diffusion equations obtained by Philip (1959) are used as the basis of the calculations. For the leading‐edge case the fetch‐height ratio for 90 per cent of the adjustment to be completed varies from 140 at a height of 0·5 metres to 530 at a height of 50 metres. The solution has application over a wide range of wind speed. For the case of horizontal uniformity and following an abrupt change in surface flux, 90 per cent of the adjustment is completed in 0·45 min at a height of 0·5 m increasing to 86 min at a height of 50 m.It is suggested that these values indicate that the choice of site and conditions for micrometeorological research is critical, and that disparity between a number of experiments may be a consequence of failure to satisfy these basic requirements.
Measurements of lagrangian and eulerian properties of turbulence at a height of 2,500 ft
Authors: Angell J. K. 
Published: February 2007

AbstractDuring the summer of 1962, super‐pressured, constant‐volume balloons (tetroons) were flown past wind‐vane instruments carried on a barrage‐balloon cable at Cardington, with the primary purpose of comparing the values of vertical velocity spectral density, S (n), obtained from the two sets of data. Based upon 25 comparisons at a mean height of 2,400 ft, on the average the maximum in the nS (n) spectrum derived from the radar‐positioned tetroons occurs at about one‐third the frequency of that derived from the wind vanes, i.e., on average the ratio, β, of Lagrangian to Eulerian scale is about three. There is a significant correlation of — 0·73 between turbulence intensity and log β, with the regression line indicating a β value of one at a turbulence intensity of 0·35 and a value of seven at a turbulence intensity of 0·05. Both factors in the turbulence intensity (mean wind speed and root‐mean‐square vertical velocity) contribute to this significant correlation, with the mean wind speed of greater influence. A comparison of five pairs of morning and afternoon tetroon flights for which lapse‐rate data are available shows that in all five cases β increases as the atmospheric stability increases.At frequencies between 0·1 and 1·0 cycles per minute, three theodolite‐positioned flights suggest that the tetroon vertical velocity spectral density is proportional to between n−5/3 and n−2, where n is frequency. Since the latter value would be in agreement with the theoretical expectation for Lagrangian‐type data, this result is consistent with the assumption that, basically, the tetroons are following the vertical air motion.Based upon 34 cases, there is evidence that surface frictional effects extend to at least 2,500 ft, with the tetroons moving across the surface isobars toward low pressure with a modal angle of 10–20 degrees and the tetroon speed being subgeostrophic to the extent of 1–2 m sec−1.
Comparison of bivane and sonic techniques for measuring the vertical wind component
Authors: Kaimal J. C. , Cramer H. E. , Record F. A. , Tillman J. E. , Businger J. A. , Miyake M. 
Published: February 2007

AbstractA comparison test between a bivane and two sonic anemometers is described. Results of spectral computations for two runs show agreement between instruments in a frequency range between 0·007 and 0·375 cycles sec−1. Coherence plot shows good agreement over the entire range between the two sonic anemometers and up to 0·15 cycles sec−1 between the bivane and either sonic anemometer.
Some velocity and momentum‐flux statistics derived from transosonde flights
Authors: Angell J. K. 
Published: February 2007

AbstractThe wind speeds derived from 300 and 250 mb constant‐level balloon (transosonde) flights from Japan are found to be significantly greater than the wind speeds obtained from rawins and the geostrophic or gradient winds obtained from synoptic maps. This is partly due to a bias in the conventional data and perhaps partly due to horizontal entrainment of the transosondes into the jet‐stream core. Products of 2‐hour average zonal and meridional, geostrophic and ageostrophic velocity components obtained from transosonde trajectories indicate a northward ageostrophic flux of angular momentum in middle latitudes equal to about one‐fourth of the geostrophic flux. the product of 12‐hour average vertical and zonal velocity components indicates an upward flux of angular momentum in middle latitudes at 300 and 250 mb, thus implying that the downward flux of angular momentum in these latitudes is maintained by relatively small‐scale eddies.Temperature changes along transosonde trajectories suggest that on the average there is upward air motion on the ridges and downward air motion in the troughs. In conjunction with the mean position in the ridge‐trough pattern of the maximum ageostrophic flow to north and south, an indirect circulation in the meridional plane (Ferrel Cell) is postulated for middle latitudes.
A further note on horizontal dispersion from an instantaneous ground source
Authors: Gee J. H. , Davies D. R. 
Published: February 2007

AbstractThis paper is written as a sequel to a previous note by Gee and Davies (1963), where it was shown that the introduction of a shearing advection term into the diffusion equation is significantn for an instantaneous source of the type discussed by Saffman (1962). A second additional term, suggested by Matsuoka (1961), has been introduced into the diffusion equation and the analysis shows that this term also has a significant effect on the properties of the cloud.
Stratospheric dynamics north of 40°N
Authors: Hare F. K. 
Published: February 2007

AbstractKinetic energy in middle and high latitudes, at levels above 20 km, increases throughout winter until the final warming, which supports the view that frictional dissipation is dynamically unimportant at these levels. A climatology of wave disturbances is presented for the years 1958‐61, little support being found for a special role for bipolarity in instability. Comments are made on the pronounced layer structure shown in the wind profiles and the regular ozone‐sonde records. It is suggested that the next stages of research in stratospheric meteorology should be directed towards the layer structure.
Concerning the similarity theory of A. S. Monin and A. M. Obukhov for the turbulent structure of the thermally stratified surface layer of the atmosphere
Authors: Calder K. L. 
Published: February 2007

AbstractThis paper considers the theoretical basis of the Monin‐Obukhov similarity theory for the turbulent, thermally stratified, surface layer of the atmosphere. It is shown that the classical form of the similarity theory cannot be applied legitimately to the variances of the horizontal components of the wind velocity fluctuation. This limitation of the theory has recently been suspected on the basis of observational data, although its theoretical demonstration emphasizes the need for caution when attempting to apply similarity theory to other characteristics of the surface layer turbulence that are currently of interest.
Soil moisture deficit and water‐table depth in London clay beneath neutral grassland
Authors: Coleman J. D. , Farrar D. M. 
Published: February 2007

AbstractDuring the period 1954 to 1964 the amount of water was estimated and the depth of the water‐table was measured in a soil profile beneath meadow grass at a site on London clay at Uxbridge, Middlesex.Each winter the soil profile was saturated and draining freely and the water‐table was within six inches of the surface. During the spring and summer the soil profile dried out from the surface downwards with a corresponding lowering of the water‐table. By late autumn the water‐table reached a depth of six feet, and the moisture deficit in the soil profile reached a value of from five to six inches. Re‐charge of the soil profile to the winter conditions occurred in late autumn or early winter.Measurements of humidity, sunshine, wind, temperature and other data were used to calculate the monthly potential evaporation, and this information, combined with rainfall data, permitted the calculation of the total deficit of soil moisture at any time from that held at field capacity.For the particular site investigated, the observed depth of the water‐table at any season varied linearly with the calculated moisture deficit in the soil profile beneath the grass, thus providing a simple method for continuously logging the moisture deficit in the soil. The result also provides a basis for correlating weather data with moisture conditions in the soil beneath roads; the moisture conditions are largely controlled by the depth of the water‐table.
On the critical liquid water concentrations of large hailstones
Authors: Macklin W. C. , Bailey I. H. 
Published: February 2007

AbstractConsiderations of the collection efficiencies of large hailstones, the local increase in the rate of heat transfer due to surface irregularities, and possible increases in critical liquid water concentrations at high Reynolds numbers give some support to the conclusion of Browning (1966) that large hailstones grow closer to the wet‐growth limit than formerly supposed.
The propagation of groups of internal gravity waves in a shear flow
Authors: Bretherton F. P. 
Published: February 2007

AbstractThe propagation in a shear flow of travelling internal gravity waves of short wavelength is investigated by the W.K.B. approximation. This implies that the Richardson number is large. It is shown that a wave group moves with the local group velocity defined in terms of the dominant wavenumber, the absolute frequency and horizontal components of wavenumber being constant. The wave energy carried by a wave packet varies, being proportional to the frequency relative to a frame moving with the local mean wind. A wave packet, on this approximation, can never pass through a critical level at which its horizontal phase velocity is equal to the mean wind, nor is it reflected there.These results imply restrictions on the propagation of internal gravity waves from the troposphere to the upper atmosphere.