bluuebunny/crossref_metadata_2025_split huggingface dataset:
A laboratory study of the ice nucleating properties of some mineral particulates
Authors: Roberts P. , Hallett J. 
Published: February 2007

AbstractLaboratory studies using a microscope cold stage with controlled humidity environment have been carried out on the ice nucleation and preactivation properties of several naturally occurring particulate substances. For initial nucleation water saturation was necessary, but below a critical temperature a constant ice supersaturation (water subsaturation), was sufficient. The values of both temperature and supersaturation depended on the substance. In preactivation the behaviour was similar but with a higher initial and critical temperature. Typical values are : for kaolinite, initial nucleation − 10·5, − 19°C, 20 per cent; preactivation − 6, − 11·5°C, 12 per cent: montmorillonite, − 25, below − 27°C; preactivation − 4, − 13·5°C, 14 per cent. The first temperature gives one ice crystal in 104 particles; the second is critical for nucleation at water subsaturation. The low values of supersaturation required for nucleation suggest that preactivation is caused by the freezing of a supercooled, adsorbed, liquid‐like layer, rather than by the retention of ice embryos in cavities. A necessary condition for the measurement of the ice nucleating ability of particles from an air sample is that they must not be heated to a temperature above at least − 5°C or subjected to a relative humidity over ice of less than about 35 per cent before the measurement is made.
Recent spectra of atmospheric turbulence
Authors: Busch N. E. , Panofsky H. A. 
Published: February 2007

AbstractSpectra of atmospheric turbulence recently measured at various heights and sites under a variety of stability conditions have been analysed and compared. The results are:

In regions over which the spectra obey −5/3 power laws, the ratio of the lateral to the longitudinal spectra shows fair agreement with the 4/3 ratio predicted by the Kolmogorov hypothesis for the inertial sub‐range. The vertical‐longitudinal ratio has a similar tendency.
Dissipation rates computed from the longitudinal spectra seem to be consistent with the hypothesis that dissipation is balanced by the total production of mechanical and convective turbulent energy, provided that the turbulence is in equilibrium. In transition from rough to smooth terrain, dissipation exceeds the other terms.
Vertical‐velocity spectra obey Monin‐Obukhov similarity theory up to a height of about 50 m. Their shapes are reasonably uniform, the major change with stability being a change of scale of the wave number axis, i.e., any characteristic nondimensional wave number is a function of z/L only. This function appears to be the same as the relation between the normalized dissipation and z/L. These results are consistent with previously measured Kolmogorov constants and with measured ratios of standard deviation of vertical velocity to friction velocity. Up to about a height of 50 m the wavelengths of the maxima of the logarithmic spectra increase linearly with height and more slowly thereafter, up to about 300 m. The spectra in stable air above 50 m suggest the existence of a buoyant sub‐range.
Longitudinal spectra do not obey similarity theory in a number of ways. The wavelengths do not scale with height, and there may be differences between sites when the spectra are plotted in similarity coordinates.
Spectra over the sea seem to have relatively more energy at low frequencies than those over land.
The dispersion of a puff of passive contaminant in the constant stress region
Authors: Chatwin P. C. 
Published: February 2007

AbstractProperties of a dispersing cloud of passive contaminant released from an instantaneous source near the ground in a neutral atmosphere are investigated theoretically. The mean wind satisfies the logarithmic law, and it is assumed that the vertical turbulent transfer can be described by means of an eddy diffusivity. By using some of the results of the Lagrangian similarity theory of Batchelor, it is shown how useful results may then be obtained from the equation describing the distribution of concentration. In particular, expressions are derived for the position of the centre of mass of the cloud and for its downwind and vertical spreads as functions of the time after release. The distribution of material at a given height is also investigated. The paper concludes with a brief discussion of the results and of other applications of the type of technique presented here.
The collection efficiencies of hailstones
Authors: Macklin W. C. , Bailey I. H. 
Published: February 2007

AbstractThe collection efficiencies of smooth spheres and artificial hailstones have been determined experimentally. There is no significant difference between the values for the artificial hailstones and those for smooth spheres of the same cross‐sectional area. However, the results are generally lower than those predicted by the theory of Langmuir and Blodgett, particularly at low airspeeds. Using these data the critical liquid water concentrations for large natural hailstones have been calculated. These are not markedly dependent on hailstone radius and, for a cloud droplet radius of 15 μ, are approximately 3 to 5 g m−3 and 4 to 7 gm−3 at the −20 and −30°C levels respectively.
Estimations from geostrophic trajectories of horizontal diffusivity in the mid‐latitude troposphere and lower stratosphere
Authors: Murgatroyd R. J. 
Published: February 2007

AbstractZonal and meridional diffusivities Kxx and Kyy have been found at mid‐latitudes from the spreads of sets of geostrophic trajectories at levels between 700 mb and 30 mb during each season of 1965. Values have been calculated using the relationship R = e−PT cos qr for the form of the corresponding Lagrangian autocorrelograms. In addition a similar set of Eulerian data has been analysed to obtain autocorrelograms and by comparison with the trajectory data Eulerian‐Lagrangian scale relationships have been obtained.The results show values of Kxx ranging from 0·2.106 to about 20.106 and Kyy from 0·2. 106 to about 6.106 m2 sec−1. In both cases the lowest values are found in the summer stratosphere and the highest in the spring stratosphere and in the upper troposphere in winter. Their distributions principally follow that of the wind variances. Integral time scales are mainly between 5 and 30 hours meridionally and 10 and 50 hours zonally and are greatest in the stratosphere and lowest in the mid‐troposphere. The contributions of damping and harmonic effects to these time scales are discussed. Comparison of the Lagrangian and Eulerian time scales indicates a mean value β of about 0·6 for their ratio with the meridional values smaller than the zonal values.
Some computations of meridional flow, angular momentum and energy in the atmosphere based on IGY data for latitude 30°N
Authors: Murray R. , Parker A. E. , Collison P. 
Published: February 2007

AbstractUsing basic data extracted from daily hemispherical cross‐sections constructed at 30°N for March, June, September and December 1958, extensive numerical calculations of mean meridional flow, angular momentum flux and energy flux (i.e. sensible heat, latent heat, potential and kinetic energy) were carried out, and the principal results are reported. Most of the computations are broadly in agreement with earlier estimates; the main differences are uncertainties concerning the energy transports.
Inviscid flows of stably stratified fluids over barriers
Authors: Pao Y.‐H. 
Published: February 2007

AbstractSteady, inviscid, incompressible, two‐dimensional flows of stably stratified fluids over a barrier or barriers are examined theoretically. The density gradient anduρ1/2are assumed to be constant upstream, where ρ is the density anduis the horizontal velocity. Exact solutions of large amplitude waves valid for arbitrary Richardson numbers are obtained for barriers of finite height in a semi‐infinite domain or in a confined channel. These barriers are constructed from vortex pairs and doublets.
Relations of radiation fluxes over natural surfaces
Authors: Idso S. B. , Baker D. G. , Blad B. L. 
Published: February 2007

AbstractRadiation fluxes over surfaces of bare soil and short grass sod were measured on clear days at St. Paul, Minnesota. Widely diverse types of daily cycles describing the hourly dependence of net upon net solar radiation were found. Heating coefficients depended as much upon atmospheric radiative properties as upon surface properties. Causes for these relations are proposed and tentatively verified experimentally.The accuracy of regressions of solar on net radiation is shown to depend upon the uniform distribution of data points extending to the region of the origin. Controversies in the literature are illuminated by this analysis, both theoretically and experimentally. Two equations relating the slope of the regression of solar on net radiation to albedo are also considered. Finally, a relation between the long‐wave radiation balance and the heating coefficient proposed by Ekern (1965) is qualitatively substantiated.
Experimental studies of the effect of electric fields on the growth of cloud particles
Authors: Latham J. 
Published: February 2007

AbstractStudies have been made in Yellowstone Park of the factors governing the growth of hydrometeors in natural clouds of ice crystals, droplets and supercooled droplets. In the majority of experiments an ice sphere or water drop was rotated through a droplet cloud or crystal stream and the mass MF of material collected in time γ was measured as a function of collector diameter D, crystal or droplet diameter d, impact velocity V, temperature T and, particularly, the strength of the electric field F in the vicinity of the growing particle. The approximate ranges of parameters attainable were F, 0 to 1,600 V.cm−1; T, + 20 to −15°C; V, 10 to 500 cm s−1; d, 10 to 150 microns; and D, 100 to 2,000 microns.It was found that electric fields could exercise a marked influence upon the growth rates of ice particles exposed to ice crystals, ice spheres exposed to supercooled droplets and water drops exposed to cloud droplets at temperatures warmer than 0°C. In all cases where the measured growth in the presence of a field was significantly different from that in the absence of a field the function of the field was to accelerate the growth rate.The aggregation of ice crystals was found to be unaffected by fields below about 500 V.cm−1 but the growth rate increased rapidly as F was increased above this value and attained about twice the field‐free value in a field of 1,500 V.cm−1. In view of the large size of the ice crystals the primary effect of the field was probably to increase the aggregation efficiency not the collision cross‐section. The most significant effect of electric forces on the growth of solid or liquid particles by the collection of droplets was to produce a rapid increase in the growth rates as F increased above a threshold value of about 1,000 V.cm−1. The growth rate at F = 1,600 V.cm−1 was typically about twice the field‐free value. The observed enhancement of the growth rate in these high fields is probably a consequence of increased collision efficiencies.The variation of the measured growth rates of all types of particle with the parameters D, d, V and T were generally consistent with laboratory measurements of previous workers. No evidence was found for the triggering of growth by electric fields or for enhanced growth in fields of magnitudes occurring within non‐precipitating clouds.
Evaporation from a papyrus swamp
Authors: Rijks D. A. 
Published: February 2007

AbstractEvaporation from an old stand of papyrus was estimated by the Bowen ratio method. It was found that about 30 per cent of the net radiation reaching the top of the canopy was converted into sensible heat. The layer formed by the heads of the papyrus also seemed to act as a major resistance to turbulent exchange of water vapour from the undergrowth. Evaporation from an old stand of papyrus was estimated to be 60 ± 15 per cent of Penman estimates of evaporation from open water.
Atmospheric edge waves
Authors: Garrett C. J. R. 
Published: February 2007

AbstractIn an isothermal windless atmosphere Lamb's wave, the energy of which decays exponentially with height, propagates non‐dispersively with the speed of sound. In the real atmosphere the speed of sound and the wind speed vary with height, but it is known that an edge wave similar to Lamb's wave is still possible. Assuming the wind speed and variations in the speed of sound to be much less than some typical sound speed, this atmospheric edge wave is shown to have group velocity given approximately byWhere ω is the wave frequency, c̄ the mean of the sound and wind speeds weighted with the energy density of the basic Lamb wave, and D is a positive dispersion coefficient defined in terms of a simple integral of the departures of the sound and wind speeds from their weighted means. Expressions are derived for the dispersive effect of a change in the sound or wind speed at any height, and these are evaluated for a particular model atmosphere. It is shown that the effect of horizontal inhomogeneities in the atmosphere is merely to average the long wave speed and dispersion coefficient along the great circle path from source to receiver. The theory is compared with the results obtained from microbarograms of pressure pulses from large atmospheric explosions, but it is found that the paucity of atmospheric data makes it difficult to use these results to estimate winds above sounding heights on the path from source to receiver. Atmospheric edge waves are shown to be rather insensitive to the upper boundary condition in general, though the effect on microbarograms of coupling between the edge wave and waves propagating high in the atmosphere is discussed, and various decoupling mechanisms, including dissipative decoupling, are described.
Observational studies in the atmospheric boundary layer
Authors: Clarke R. H. 
Published: February 2007

AbstractWinds and temperatures in the boundary layer measured during two Australian expeditions are analysed according to the similarity scheme, with the use of four stability classifications.Under conditions of deep convection there is a minimum potential temperature and a maximum velocity component in the direction of the surface wind, at a height of about 0.12 u*/f. In the very stable cases, the temperature gradient follows rather closely a z−2 law for a considerable height range from 0.08 u*/f upwards. An expression closely fitting the mean data in stable conditions is suggested for the vertical temperature structure at all levels in the boundary layer.Wind data processed in this way show, for all four stability classes, a rudimentary Ekman spiral. With deep convection the spiral is found to be reversed in sense, but the flow in the convecting layer is down the gradient of pressure. If the convective limit lies broadly within the Ekman layer, a spiral of the expected sense is found. The upper limit of the Ekman layer (as defined by the ‘spiral’) is found to lie at a height of 0.17 to 0.24 (increasing with stability) in units of u*/f. Stress and heat‐flux are apparently considerable above this level, with sub‐geostrophic wind, when deep convection is occurring.Approximations to the universal distributions of stress, eddy coefficients, mixing length and rate of degradation of mean flow kinetic energy are computed for the various stabilities. The mixing length in unstable conditions increases almost as height up to a level of about 0.08 u*/f, and then decreases, but in general appears not to vanish in stable layers above the boundary layer. In the unstable boundary layer with deep convection, the eddy transfer coefficient for heat exceeds that for momentum up to 0.12 u*/f, where it becomes infinite, and is negative at higher levels. In stable conditions the transfer coefficients for a small sample of soundings were estimated to be closely similar.The universal functions of stability, A, B and C, which enable one to compute free atmosphere wind vector and temperature, given surface conditions, have been evaluated with moderate success, although B, which essentially describes the change of wind direction with height, exhibits excessive variability. A method is suggested for computing horizontal advection in the boundary layer when this is to be ‘parameterized’ in mathematical models.The drag coefficient, in terms of free atmosphere wind, has almost a 50‐fold range, due to stability variation only. Most of the variation occurs relatively close to neutral, so warning against too ready an assumption of neutrality in practical applications.It is suggested that, for modelling purposes, it is preferable to adopt boundary layer formulations which are not too sensitive to departures from ideal conditions, and eddy coefficients, perhaps based on mixing lengths, may well provide the best approach currently available.
Solar radiation and solar activity
Authors: Kondratyev K. Ya. , Nikolsky G. A. 
Published: February 2007

AbstractUsing high‐altitude balloon soundings (1961 to 1968) and other data, it is shown that the most reliable maximum value of the solar constant is at present 1.94 cal cm−2 min−1, to an accuracy of 1 per cent. This value is observed with Wolf numbers between 80 and 100, below or above which the solar constant decreases. The maximum decrease does not exceed 2 to 2.5 per cent. The observations reveal the influence of nuclear explosions and volcanic eruptions which caused an anomalous turbidity of the upper atmospheric layers. These anomalies have been studied. The above conclusions require further confirmation using direct long‐term measurements of the solar constant outside the atmosphere.
The absorption coefficients of ozone for the Dobson spectrophotometer: A direct determination of their ratios and temperature dependence
Authors: Powell D. B. B. 
Published: February 2007

AbstractThe ratios of the absorption coefficients of ozone at the standard wavelength pairs for the Dobson spectrophotometer have been determined in the laboratory over a range of temperatures using the sun as light source. Temperature coefficients of absorption are calculated and compared with those derived from the results of other workers. Using – 55°G as the representative temperature of atmospheric ozone, new values are given for the absorption coefficients which differ from the currently accepted values.
Cross‐equatorial eddy momentum fluxes as evidence of tropical planetary wave sources
Authors: Dickinson R. E. 
Published: February 2007

AbstractThe large‐scale asymmetries in the release of latent heat in the Tropics should be an important source of planetary waves. According to planetary wave theory, such sources are accompanied by a convergence of eddy momentum flux. These planetary waves may provide eddy fluxes of momentum across the Equator from the winter to the summer hemisphere in agreement with observation.
Cospectral similarity in the atmospheric surface layer
Authors: Wyngaard J. C. , Coté O. R. 
Published: February 2007

AbstractThere are two asymptotic cases where the four parameters which determine surface layer turbulence structure reduce to three. In the unstable limit, which we call local free convection, the surface stress is no longer important. In the stable limit z no longer enters; we propose the name ‘local z‐less stratification’ for this state. In both cases explicit predictions result for various properties of the cospectra of stress and heat flux. Although the predictions are based on asymptotic arguments and therefore might be expected to hold only at large ∣z/L∣ values, data from the 1968 Kansas experiments show that most predictions are valid fairly close to neutral.
A study of the energetics of an upper stratospheric warming (1969‐1970)
Authors: Miller A. J. , Brown J. A. , Campana K. A. 
Published: February 2007

AbstractDuring the winter of 1969‐1970 when a rather intense stratospheric warming of the type restricted to the upper stratosphere occurred, we were fortunate in having a considerable number of rocketsonde observations throughout the Northern Hemisphere. In addition, the Satellite Infrared Spectrometer (SIRS) on board Nimbus 3 yielded large amounts of radiation temperature data which, when combined with the above, enabled us to construct hemispheric synoptic analyses at the 10‐, 5‐, and 2‐mb levels, for seven days during the warming event.Employing these analyses along with the daily objective analyses from 1,000‐30 mb, we computed certain of the major energy transformations for the troposphere and lower and middle stratosphere. It was found that the middle stratospheric warming event was of a direct baroclinic type, forced from below. Also, we noted that if the warming is to propagate into the lower stratosphere, it is necessary to reverse the normal eddy kinetic to eddy potential energy transfer in that region so that it operates in a direct baroclinic sense.
Studies of turbulence in the surface layer over water (Lough Neagh). III. Wave and drag properties of the sea‐surface in conditions of limited fetch
Authors: Garratt J. R. 
Published: February 2007

AbstractWave and aerodynamic properties of the sea surface at Lough Neagh, Northern Ireland, are described with mean wind speed u (at a height of 10 m) varying from 4 to 8 m s−1 and fetch F varying from 8 to 22 km.The sea surface at Lough Neagh is characterized by wind induced waves of dominant period 2 to 4 s and a wave spectrum depending upon u and F, with a steep low frequency face (at frequency nf), sharp peak (at no) and high frequency region with ‘energy’ proportional to frequency to a variable power β in the range —4 to —5. The ‘constant’ of proportionality αg2 in the relation ϕ(n) = αg2n−β appropriate to the equilibrium range is variable between 6 and 12 (where unless stated to the contrary n in numerical expressions is in cycles s−1)‐ mean of 7·9 ‐with a mean β of —4·5, which compares to Phillips' overall mean value of αg2 of 7·2 with a mean β close to —5.Our data, and those from other sources, suggest the following relations, valid over a range of the dimensionless fetch gF/u2 from 102 to 105,

And

The first two are found to imply σh = 1·4 n−2o.The third relation is interpreted through identification of nf with the transition frequency separating a linear from an exponential wave growth.Our data are consistent with the idea of Kitaigorodskii that zo (u*) depends also upon the degree of wave development σ = gσh/u*2. At Lough Neagh σ* ∼ 10–40, implying zo is closely related to u* as is found to be the case using logarithmic wind profiles.There is evidence that

Suggested by earlier Russian work for similar values of σ*.There is no evidence that wave power impresses itself upon the turbulence spectra of the air for values of height/wave amplitude ratio as low as 3·3:1.