bluuebunny/crossref_metadata_2025_split huggingface dataset:
A new dimensional approach to the problem of flux‐gradient relationships near the ground
Authors: Bernstein A. B. 
Published: February 2007

AbstractApplication of the dimensional method of vector lengths to the continuity equations for momentum, heat, and any conservative scalar property whose mass concentration is S, yields a flux‐gradient relationship of the form \documentclass{article}\pagestyle{empty}\begin{document}$ \[ \frac{{K_z }} {{r_\omega S\sigma S}}\frac{{\partial \overline S }} {{\partial z}} = f_S \left\{ {\frac{{KgzH}} {{\rho c_p T\sigma _{\omega ^3 } }}} \right\} \] $\end{document}Which is identical to the Monin‐Obukhov relationship except that the governing parameter u* is replaced by σω and the governing parameter S* is replaced by γωS σS. This formulation cannot be adequately tested with existing data due to a systematic underestimation of the rapid‐response statistics under non‐neutral conditions. This underestimation is the result of improper choice of sampling period and interval between successive measurements. While a satisfactory correction may be applied to the stress, permitting examination of the Monin‐Obukhov formulation, no such correction procedure is possible with respect to γωS σS and σω.
The free‐convection temperature profile
Authors: Deardorff J. W. , Willis G. E. 
Published: February 2007

AbstractMeasurements of horizontally averaged temperature within a convection chamber suggest that as the Rayleigh number is increased, there is a tendency for Priestley's constant H∗︁ of the free‐convection temperature profile to approach the atmospheric value. An extrapolation of this trend implies that an atmospheric layer in which the temperature gradient varies as z−4/3 is truly representative of free convection and is not influenced by very small values of mean wind shear.In Townsend's open‐box convection experiment, the downdraught which persisted at the location of temperature measurements is considered here to have suppressed the appearance of a — 4/3 power region and perhaps to have caused an extended — 2 power region in the temperature gradient.A small‐scale field experiment is proposed to settle the controversy of the power dependence of the free‐convection temperature gradient in windless conditions.
A theoretical study of the ice accretion process
Authors: Macklin W. C. , Payne G. S. 
Published: February 2007

AbstractA theoretical study has been made of the assumptions underlying the simple heat balance relations which have been used so far to predict the surface temperatures of ice deposits being formed by the accretion of supercooled water droplets. Calculations have been made of the freezing and subsequent cooling times of a thin water film on the surface of a ventilated sphere initially at a uniform temperature. It is demonstrated that this effectively simulates hailstone growth. The calculations show that both the freezing and cooling processes are dominated by the sphere temperature although, during freezing, the temperature of the water film may rise to a value close to 0°C. They also show that, except at sphere temperatures within a few degrees of 0°C, the freezing time of the water film is short compared with the total time taken to remove the latent heat of fusion by the forced convection process. The reason for this is that the heat of fusion is first conducted rapidly into the sphere, and then more slowly dissipated through the air boundary layer on the surface of the sphere to the environment.Values of the freezing and subsequent cooling times of the water film are presented for various values of the ambient temperature, sphere radius and film thickness. Film thicknesses have been related to the radii of the cloud droplets by a semi‐empirical relation. The liquid water concentrations required to maintain a sphere at a steady temperature have been computed and found to compare well with those given by the simple heat balance relation for a spherical hailstone. Thus, although the simple heat balance relations completely ignore the physical processes involved in the accretion of individual droplets, they are useful for predicting values for the mean temperatures of an accreting surface in a steady state situation.
Continuous regular pressure oscillations in the atmosphere at night
Authors: Shrestha K. L. 
Published: February 2007

AbstractContinuous and very regular pressure oscillations with periods ranging from 15 to 120 sec and having magnitudes of 1 to 6 μ bar were observed on clear and calm nights at two of the three microbarograph stations near Brisbane, Australia. Their dependence on the topography and the stability of the lower atmosphere resembles that for lee waves observed behind ridges.
Characteristics of vertical velocity fluctuations observed on a 430‐m tower
Authors: Kaimal J. C. , Haugen D. A. 
Published: February 2007

AbstractDuring the summer of 1963, sonic anemometers were mounted at 46, 137, 229 and 320 metres on a 430 metre tower to measure turbulent fluctuations in the vertical velocity component. Mean horizontal wind speeds and temperatures were measured at 12 levels on the tower.Characteristic behaviour of power spectra for four typical stability conditions are described. Evidence of an inertial subrange is found at all levels regardless of stability. Analysis of the rate of dissipation, ϵ, indicates that there is no simple relationship which can describe its behaviour with height for all conditions. Its behaviour is shown to change with thermal stratification; ϵ remains relatively constant with height during well‐established convection but decreases rapidly above 46 m when the temperature gradient is stable. It is also shown that ϵ is roughly proportional to the product of the third power of the standard deviation of the vertical velocity component and the wave number of its logarithmic spectral peak.The data from the sonic anemometers provide some additional information on the structure of convection during very unstable lapse conditions. Analyses of coherence between successive levels indicate the presence of a second generation of convective elements above the plume convection generally observed near the ground. The transition layer is estimated to be in the vicinity of 100 m. The scale of turbulence for the top three levels shows an initial increase with increasing instability followed by a decrease. It is conjectured that this decrease is a consequence of the fact that the second‐generation convective elements move faster than the wind speeds indicated at the level of instrumentation.
Energy‐preserving integrations of the primitive equations on the sphere
Authors: Grimmer M. , Shaw D. B. 
Published: February 2007

AbstractLong‐term global integrations of the primitive equations for the free‐surface model are performed using spherical polar co‐ordinates. Two methods are used to overcome the computational drawback of excessive resolution near the poles. In the first, time‐steps vary latitudinally on a grid with constant angular increments. Stable integrations result, in which the evolutions closely match (save for phase‐truncation due to divergence) those of the analytic solution of the non‐divergent vorticity equation for initial data in which non‐linear interactions vanish. In the second set of integrations zonal resolution varies latitudinally, and the resulting differential phase‐truncation causes spurious interactions which lead to rapid departure from the analytic solution. In both cases finite difference approximations are used which preserve domain sums of mass and of total energy (kinetic plus potential), in analogy with properties of the continuous equations. The space‐differencing method, together with the time‐smoothing inherent in the variable time‐step scheme, may have helped to suppress non‐linear instability in the first set of integrations.
An analysis of the chemical composition of rain‐water and air over the British Isles and Eire for the years 1959–1964
Authors: Stevenson Catherine M. 
Published: February 2007

AbstractThe results of an analysis of the chemical composition of precipitation and air over the British Isles and Eire are presented. Tables are given showing the median concentrations of S, Cl, Na, K, Ca and nitrogen in ammonia and nitrate, and maps are presented to indicate the variations in sources for different chemicals. The errors in the sampling technique are discussed.
The white box: The mean mechanics of the cumulus cycle
Authors: Fraser A. B. 
Published: February 2007

AbstractA region surrounding a cumulus cloud is defined in such a way that (when virtual temperature effects are neglected) there is no sensible heat transfer across the boundaries of the region. This simplifies the discussion of the interaction between the cumulus and its environment. A model of the region, which is called the white box, is developed and an estimate is made of the net vertical mass transport within it as a function of height. Rain and cloud radiation have the effect of modifying this transport and may be described in terms of it. If the requirements of continuity are satisfied by means of an alteration of the wind profile of the environment downstream, the wind near the base of the cloud downstream is increased. It is shown that cumulus convection can destabilize as well as stabilize its environment.
A pressure oscillation in a 10‐level atmospheric model
Authors: Benwell G. R. R. , Bretherton F. P. 
Published: February 2007

AbstractA pressure oscillation in the 10‐level primitive equation model of Bushby and Timpson (1967) has been diagnosed as a standing inertio‐gravitational wave in the external mode. A small modification to the linearized balance equation used to define the initial state has resulted in its elimination. Although the broad development of the pressure field is unaffected, significant changes have appeared in the rainfall. The speed of propagation of external gravity waves in the model is about 285 m/s, substantially less than for a comparable continuous atmosphere.
The regions of formation of atmospheric ozone
Authors: Brewer A. W. , Wilson A. W. 
Published: February 2007

AbstractThe nature and magnitude of the source of the natural ozone of the atmosphere is discussed and the results of calculations of the local rates of production in the periods January‐February and July‐August are given. The effect of different assumptions and models on the deduced source regions and source strengths is demonstrated. It is concluded that the most satisfactory result is obtained using solar ultraviolet intensities recently measured in the stratosphere. It is possible that there may be some catalytic destruction of ozone by water vapour, but below 35 km the effect must be small.
Transport of gases to and from surfaces with bluff and wave‐like roughness elements
Authors: Chamberlain A. C. 
Published: February 2007

AbstractWind tunnel experiments have been done on the transport of a radio‐active vapour of thorium B, and water vapour, to and from surfaces with spherical, cylindrical and wave‐like roughness elements. The results are analysed in terms of the dimensionless number B of Owen and Thomson.For values of the roughness parameter u* z0 v−1 between 10 and 1,000, the results were found to conform approximately to Owen and Thomson's empirical formula
\documentclass{article}\pagestyle{empty}\begin{document}$ \[B^{ - 1} = \alpha \left({\frac{{u_* h}}{\nu }} \right)^m \left({\frac{\nu }{D}} \right)^n \] $\end{document}
Where h (= 30 z0) is the equivalent sand roughness, D the diffusivity of the vapour, and α, m and n are constants with values 0·5, 0·45 and 0·8 respectively. Experiments with aerodynamically smooth surfaces give results in accordance with von Kármán's equation.Wind profiles over large bodies of water imply rather small values of the roughness length and u* z0 v−1 generally lies in the range 0·1 to 10. In this region, the bluff‐body effect on momentum transport is small, and is counteracted by the fact that D for water vapour is greater than v. As a result, B−1 is small, and the resistances to transport of momentum and water vapour are nearly the same. Experiments on the rate of evaporation of water in a tank in the wind tunnel give values of the bulk evaporation coefficient, referred to a height 5 cm above the surface, in good agreement with theory.
A micrometeorological study of velocity profiles and surface drag in the region modified by a change in surface roughness
Authors: Bradley E. F. 
Published: February 2007

AbstractThis paper describes experiments in the lower atmosphere in which the wind passes from one surface to another with different roughness. Observations were made of the variation of surface stress, and of the development of velocity profiles in the region of flow modification over the downwind surface. Measurements are compared with the theories of Taylor, Elliot, and Panofsky and Townsend, and with the growth of a boundary layer on a flat plate. A large proportion of the surface stress adjustment occurs rapidly after the transition in agreement with Taylor's assumption. Velocity changes agree fairly well with the Panofsky and Townsend theory in the smooth‐rough direction, but not so well in the reverse. Growth of the modified region follows the 4/5 power law of boundary layer growth. It is concluded that the height/fetch criterion for a good micrometeorological site is about 1/200.
A shearing stress meter for micrometeorological studies
Authors: Bradley E. F. 
Published: February 2007

AbstractA shearing stress meter (drag plate) for general use in micrometeorological studies is described. The mechanical principle applies to a large size range, though the instrument described specifically is of 3 ft (91 cm) diameter for installation in turf sites. The drag force is measured using strain gauges, and an absolute calibration system is built into the mechanism. The resolution of the instrument is about 0·02 dyne cm−2, and it will tolerate gusts of over 10 dyne cm−2 without damage. A detailed description is also given of the installation and operating procedure, attention to which is essential for reliable measurements.
Solar radiation on the south coast of England
Authors: Rees A. R. 
Published: February 2007

AbstractThree years' data of incoming measured solar radiation at the Glasshouse Crops Research Institute are used to assess the radiation climate of the south coast. Radiation in both summer and winter is higher than at other stations in this country; this is, however, only partly attributable to the longer duration of sunshine because radiation is higher than would be expected from the longer duration of sunshine alone. A similar effect at Aberporth results from clean air, but despite the low level of pollution on the south coast, peak clear‐weather values are not abnormally high. Supplementation occurs on days that are not wholly clear; it is suggested that this is a result of reflection from orographic cloud.
A study of the effect of haze upon Umkehr measurements
Authors: Deluisi J. J. 
Published: February 2007

AbstractThe effect of atmospheric haze upon Umkehr observations is calculated in two ways. First, observed Umkehr curves are compared with computed Umkehr curves reconstructed from simultaneous direct soundings of the vertical ozone distribution. The difference between the two curves gives the ‘experimental’ haze effect. In the second method, Umkehr curves are computed for model atmospheres with and without haze, the difference giving a ‘theoretical’ haze effect. When the two haze‐effect curves are normalized to zero for a solar zenith angle of 60°, both exhibit the same characteristics, viz., the ‘correction’ to be subtracted from an observed (with haze) curve is negative at all solar zenith angles, the correction reaches a maximum near 81°, and there is a second small reversal near 87–88°. Application of the derived haze corrections in the Umkehr evaluation procedure results in slightly higher ozone content at and just below the main maximum and slightly lower ozone content elsewhere.
Observational studies of the general circulation of the Tropics: long term mean values
Authors: Kidson J. W. , Vincent D. G. , Newell R. E. 
Published: February 2007

AbstractData from 298 stations between 45°N and 30°S have been processed for the period July 1957 to December 1964. The mean wind and temperature fields are presented together with the momentum and heat fluxes for two three month seasons, December‐February and June‐August. The tropospheric results were obtained from objective analysis of the long term station means and the stratospheric results from latitude band means giving equal weight to data from odd and even years so that the biennial component has been virtually eliminated.The mean temperature cross‐sections show little seasonal variation in the tropical troposphere and gradients are small. The maximum temperature is in the vicinity of 5°S during the southern summer but moves to 20°N during June‐August as a consequence of stronger heating over the continents. In the tropical stratosphere the seasonal variation is from lower temperatures in December‐February to higher temperatures in June‐August. The mean zonal wind pattern shows the tropical easterlies to be stronger and to occupy a greater range of latitudes in the upper troposphere during June‐August. The Hadley circulation obtained appears quite reasonable with the winter hemisphere cell predominating and extending over the Equator.Although all three components of the momentum flux were evaluated for the troposphere, only the transient eddy contribution could be obtained for the stratosphere. A strong flux is observed in the upper equatorial troposphere directed into the summer hemisphere. The sensible heat‐flux in the middle troposphere is equatorward in the Tropics of both hemispheres and a small transport into the summer hemisphere is noted. This equatorward flux is countergradient in both hemispheres except during the northern summer. The mean motion transport of total energy is about an order of magnitude larger than the eddy transport at the Equator and supplies energy to the winter hemisphere.The zonal and eddy forms of kinetic energy and available potential energy have been evaluated for the tropical troposphere together with all conversions between them except for that by transient eddies between available potential energy and kinetic energy. On the average, kinetic energy contents are about twice as large as available potential energy contents and the momentum flux conversions are larger than those involving heat fluxes. The conversion by the mean motions, however, is largest of all over the range 24°N‐24°S and leads to a rejuvenation time of some 3–5 days for the zonal kinetic energy. This conversion appears to be sufficiently large to offset the destruction in middle latitudes.Taken together, the results presented here give a consistent pattern for the tropical circulation. The direct Hadley cell is seen as a source of both heat and momentum which are distributed by the eddy fluxes. The energy supply for the mean cell is thought to be the latent heat of condensation in its ascending branch.
Energy flux and convergence patterns in the lower and middle stratosphere during the IQSY
Authors: Newell R. E. , Richards M. E. 
Published: February 2007

AbstractThe vertical and horizontal fluxes of energy by large‐scale standing waves have been estimated on a monthly basis for the IQSY for the 100–10 mb region. A large upward flux into the region occurs in winter some of which passes into the atmosphere above 10 mb, where it may exceed the energy generated there by radiative processes. The meridional wave energy flux diverges from the 40°–60°N region and converges in both high and low latitudes in winter. The total energy flux convergence pattern shows that the polar night jet in the lower stratosphere in winter is a source of kinetic energy; when the jet collapses in the spring the same region turns into a strong sink and it is noted that while this was a gradual process in 1965 and occupied three months, there was a large absorption in March 1964 that dominated the energetics pattern in spring. The largest energy absorption occurs with the largest energy flux into the region, thus supporting previous suggestions that the spring warming is ultimately dependent on tropospheric events. The adiabatic approximation was used in the flux computations and the role of radiative processes in the observed events is briefly discussed.
Seasonal variation of kinetic energy in the atmosphere
Authors: Kung E. C. , Soong S. 
Published: February 2007

AbstractIn an attempt to broaden the observational basis of the seasonal variation of the large‐scale atmospheric circulation, Fourier analysis was applied to time series of important kinetic energy variables which were computed for a 5‐year period over the North American Continent. The variance spectra of the direct Fourier analysis are also presented.The year‐to‐year fluctuation of the seasonal variation of the energy variables is apparent. After filtering out the year‐to‐year irregularity, clear basic features of the seasonal evolution were obtained. The kinetic energy level can be described essentially by the one‐year cycle. However, the energy generation, outflow, and dissipation show an important half‐year cycle in addition to the prominent one‐year cycle.
Surface films and the production of sea‐salt aerosol
Authors: Paterson M. P. , Spillane K. T. 
Published: February 2007

AbstractThe number of condensation nuclei produced by the bursting of a single bubble in sea‐water, and detectable at a few per cent supersaturation, is shown to be markedly dependent on the film pressure of naturally occurring surface‐active material adsorbed on the surface.At low film pressures around 1 dyne cm−1 the presence of the film increases the variability of the number produced, but the number is always less than that expected for a clean water surface. With increase of film pressure the number of nuclei produced decreases markedly.The dependence of nucleus number on the state of any surface‐adsorbed film has important consequences for the sea‐to‐air transport of organic material. This is discussed.
Modification of mean flow and turbulent energy by a change in surface roughness under conditions of neutral stability
Authors: Peterson E. W. 
Published: February 2007

AbstractA theory is developed which describes the adjustment of the flow of a hydrostatically neutral fluid in the lower portion of a fully‐turbulent boundary layer, after an abrupt change in surface roughness.The model is based on the hypothesis that the horizontal shear stress is proportional to the turbulent energy. The theory postulates that the flow is primarily governed by the dominant terms of the horizontal‐momentum, continuity, and turbulent‐energy equations. The model was solved by numerical techniques on a digital computer.Unlike previous models there are no a priori assumptions about the distribution of velocity or stress, the behaviour of the nondimensional wind shear, mixing length, or momentum‐exchange coefficient in the transition region.The theory, in contrast to earlier theories, suggests the distribution of turbulent energy, as well as velocity. An inflection point is predicted in the transition velocity‐profile. The nondimensional wind shear is found to differ significantly from unity in the transition region. These predictions agree with observation.
Eigenvectors for representing the 500 mb geopotential surface over the Northern Hemisphere
Authors: Craddock J. M. , Flood C. R. 
Published: February 2007

AbstractA set of empirical orthogonal functions is produced which enable the large‐scale features of the 500 mb topography over the Northern Hemisphere to be represented with near optimal efficiency. The more important functions are described. Some of the properties of the coefficients of these functions which best represent the 500 mb charts for each day of the years 1965 to 1967 are summarized. The question of the number of functions required to obtain the most satisfactory representation of the 500 mb fields is discussed.