bluuebunny/crossref_metadata_2025_split huggingface dataset:
Exact reflectance under a cardioidal luminance distribution
Authors: Preisendorfer R. W. 
Published: February 2007

AbstractThe cardioidal luminance distribution B (θ, k) = B (θ/2, k) (1 + k cos θ), ‐ 1 ≦ k ≤ ∞, 0 ≦ θ ≦ π/2 is the general empirical form of the luminance of overcast skies. It has been found empirically (Moon and Spencer 1942) and theoretically (Chandrasekhar 1946) that the value k = 2 represents most overcast skies. The purpose of this note is to obtain the exact algebraic expression for the reflectance r (m, k) of a surface (between media of relative indices of refraction 1 and m ≧ 1) irradiated by an unpolarized cardioidal radiance distribution. In this way the classical reflectance formula of Walsh (1926) for the case k = 0 is generalized, and the approximately‐obtained numerical results of Middleton (1952) for the case k = 2, m = 4/3 are extended. In addition it is found that the function r (·, k) is essentially linear over the range 1.2 ≦ m ≦ 1.9 for each fixed value of k in the interval 0≦5 ≤ k ∞, and thus may be represented by the form: r (m, k) = a (k) m + b (k). In particular r (m, 2) = 0.141965 m ‐ 0.137709 which has a maximum deviation of 3.2 per cent from the exact values of r (m, 2) over the range 1.2 ≦ m ≦ 1.9.
Observable evapotranspiration in the Basin of the River Thames
Authors: Cochrane N. J. 
Published: February 2007

AbstractThe measurement of evapotranspiration from large land areas is, like the measurement of evaporation from large areas of water, a formidable problem and not often accurately accomplished. Nevertheless, it is essential for an engineer to try to check the results of theoretical or empirical analyses, or small‐scale experiments, against nature where natural phenomena are concerned and the results of an analysis of the hydrology of the Thames are presented herein. Conclusions favouring the Thornthwaite method are reached.
Measurements of the atmospheric potential gradient on a Canadian glacier
Authors: Adkins C. J. 
Published: February 2007

AbstractMeasurements of the atmospheric potential gradient made on a glacier at an altitude of 1,700 m showed a behaviour considerably simpler than is normally found near the ground. The nearness of the cloud, and the absence of point discharge for some kilometres gave a clear‐cut distinction between snow and rain, these almost always being associated with positive and negative fields respectively. The results suggest that the electrification processes are associated with the precipitation in both cases, and that marked electrical effects accompany the melting of snow.
Atmospheric electrical agitation
Authors: Israël H. 
Published: February 2007

AbstractThe paper shows the so‐called ‘agitation’ of the atmospheric electrical elements in relation to the atmospheric turbulence, and demonstrates in a series of examples the behaviour of the agitation and its application to the analysis of atmospheric electrical processes. We can consider it as a further element in the coupling between atmospheric electricity and meteorology. It appears that the central significance of the coupling can be seen in the various atmospheric exchange processes and their different electrical effects.
The motion in and around isolated thermals
Authors: Woodward Betsy 
Published: February 2007

AbstractLaboratory measurements show that the motion of an isolated ‘thermal’ is like that of a vortex ring. The centre is rising at slightly more than twice the rate of the thermal cap and on the edges the buoyant fluid is descending, relative to a stationary observer. As the thermal rises, mixing with outside air takes place, approximately 60 per cent at the front and 40 per cent at the rear, and the thermal traverses a cone of half angle about 15°. Heavy particles, with a terminal velocity of less than 0·4 Wc, where Wc is the rate of rise of the cap, will not escape from the thermal; whilst those with a terminal velocity exceeding somewhat less than 1·6 Wc cannot be retained in it. It is argued that the isolated thermal is the ultimate form of all convective elements in the atmosphere and that this ultimate form is generally reached between 200 and 2,000 metres from the ground.
Mean meridional circulations in the atmosphere
Authors: Tucker G. B. 
Published: February 2007

AbstractThe mean meridional circulation in winter and summer is derived as a function of latitude and height from an analysis of observed winds in the area 160°W‐0‐40°E, 75°N‐15°N. The results confirm the classical idea of a direct circulation in low latitudes, but the indirect circulation in middle latitudes is stronger than expected. An investigation of the energy released by the meridional circulation implies that it is of comparable importance to large‐scale disturbances in the energy balance of the general circulation.
Practical field instruments for estimation of radiation and of evaporation
Authors: Pereira H. C. 
Published: February 2007

AbstractA distillation instrument for the integration of radiation, described by Bellani in 1836, rebuilt in modern materials by Gunn, Kirk and Waterhouse (1945), has a thermal efficiency of over 75 per cent. The improved instrument, mounted at ground level in East Africa, with the condenser underground in constant cool conditions, had a performance that justified manufacture. Comparisons of the manufactured instruments with a Kipp solarimeter gave high linear correlations. These results show the distillation instruments, when so calibrated, to be useful for field estimations of solar radiation. Their cost is low and the daily estimate of total radiation is quickly obtained from a simple burette reading.Ten years' data for these Gunn‐Bellani integrators are compared with those from 4 ft diameter open water pans. A mounting is described for these pans in shallow revetted pits where their sides are shielded from the sun and are insulated from the soil by an air space. A linear correlation based on 164 ten‐day means accounts for 85 per cent of the variability. It appears that in the high‐altitude tropics this radiation integrator by itself can give the basic data for adequate estimate of water use by vegetation, and for control of irrigation.
Spectroscopic observations of the water‐vapour content of the stratosphere
Authors: Houghton J. T. , Seeley J. S. 
Published: February 2007

AbstractThe water‐vapour content of the stratosphere has been deduced from records of the solar spectrum observed from a Canberra aircraft at altitudes up to 48,000 ft. The spectral region 3,790‐3,860 cm−1 in the 2·7 μ band has been separated into four groups of absorption lines whose rates of growth have been studied. Measurements in an altitude chamber of the absorption of very small paths of water vapour have been used to interpret the aircraft measurements in terms of absolute values of (pressure X quantity of water vapour)½. Spectroscopic observations have been compared with measurements made by the frost‐point hygrometer. The overall results show that the water‐vapour content in a vertical column above 45,000 ft over southern England is about 4·5 μ, corresponding to a mixing ratio of 3 × 10−6, if this is assumed constant above the height of observation.
Possible meridional circulations in the stratosphere and mesosphere
Authors: Murgatroyd R. J. , Singleton F. 
Published: February 2007

AbstractA calculation has been made of the meridional circulation sufficient to transport heat between the radiational sources and sinks in the stratosphere (15‐55 km) and mesosphere (55‐80 km). Assuming that the principal heat sources are in the region of the equatorial tropopause and in the mesosphere over the summer pole, with the corresponding heat sinks near the polar tropopause and over the winter pole in the mesosphere, the main circulation patterns are found. Below 30 km there is rising air over the equator with outflow towards both poles and descent towards the tropopause in high latitudes in both hemispheres. At higher levels there is ascent over the summer pole and descent over the winter pole with a well defined flow towards the winter pole above 50 km and a more indeterminate flow pattern between 30 and 50 km. The order of magnitude of the speed of these circulations is m sec−1 horizontally and cm sec−1 vertically.The calculations were made for the solstices, equinoxes and mid‐times between them and several particle trajectories were determined. The results are in agreement with many of the observed physical features of the stratosphere and mesosphere, particularly the distribution of tracer elements.
A Markov chain model for daily rainfall occurrence at Tel Aviv
Authors: Gabriel K. R. , Neumann J. 
Published: February 2007

AbstractA Markov chain probability model is found to fit Tel Aviv data of daily rainfall occurrence. This accounts for the form of the distributions of dry and of wet spells and of weather ‘cycles’ which have been presented in earlier papers. Further aspects of rainfall occurrence patterns may be derived as well, and are found to fit the data. In particular, the distribution of the number of rainy days per week, month or other period is obtained. Numbers of rainy days in different months are apparently independent.
The role of diffusiophoresis in the scavenging of radioactive particles from the atmosphere
Authors: Goldsmith P. , Delafield H. J. , Cox L. C. 
Published: February 2007

AbstractDiffusiophoresis is the name of the phenomenon whereby particles of an aerosol, through which a vapour or gas is diffusing, experience a force which moves them in the direction of the diffusive flux of the vapour or gas. Experiments are described which show that the velocity (cm sec−1) imposed on sub‐micron particles (0·01 to 0·1 μ radius) in the case of water vapour diffusing in air, when the water‐vapour pressure is small compared with the total pressure, is governed by the equation: where dp/dx is the water vapour pressure gradient expressed in millibars per cm. This result is shown to be in excellent agreement with theoretical considerations.The absolute efficiency of diffusiophoresis in scavenging radioactive fallout particles from the atmosphere, because of cloud droplets growing by condensation, is deduced to be low. This is confirmed by a cloud‐chamber experiment in which inactive salt droplets were grown in the atmosphere of a radioactive aerosol.Furthermore, it is concluded that the wash‐out due to diffusiophoresis accounts for less than one per cent of the total observed wash‐out of nuclear‐bomb debris for each condensation cycle occurring in nature. Cloud droplets would have to undergo over one hundred condensation‐evaporation cycles on the same condensation nucleus for diffusiophoresis to be responsible for most of the observed wash‐out.
The determination of eddy diffusivity from measurements of turbulent energy
Authors: Pasquill F. 
Published: February 2007

AbstractTwo existing methods of deriving eddy diffusivity from measurements of turbulent energy are briefly reviewed, one based on the theory of the inertial sub‐range and therefore concerned with high‐frequency energy, the other purely empirical and concerned with total energy. A third method, based on the statistical theory of diffusion of particles and concerned with low‐frequency energy, is suggested.The three methods are applied in terms of some recent broad‐band spectrum measurements of the vertical component near the ground in neutral conditions, and the results compared with the eddy diffusivity K derived from the wind‐profile. The high‐frequency and total‐energy methods give the smallest spread (standard deviation near 10 per cent) in the individual estimates of K. On average K is given by the lowfrequency method (using a constant derived independently) within a few per cent, but the high‐frequency method (using one particular estimate of a constant term) underestimates by about 36 per cent. The latter discrepancy is in agreement with an earlier related test, made by R. J. Taylor, against observations of shearing stress and structure functions. Taylor's analysis suggests that the high‐frequency method should otherwise be useful in non‐neutral conditions also, but confirmation of this and thorough testing of the other methods requires further observations.
The ionisation of the atmosphere near the ground in fair weather
Authors: Law J. 
Published: February 2007

AbstractIn Part 1 observations of the positive and negative small ions in the lowest 2 m of the atmosphere near Cambridge are described, showing that the conductivity decreases with height in this region under most conditions. Simultaneous observations of the space‐charge density are incompatible with the theory that the convection current is small compared with the conduction current, and are supported by observations of the vertical electric field. Estimates of the size of the convection current and the vertical distribution of space charge have been made.Observations at the time of the ‘sunrise effect’ show that the increase in the field is associated with an increase in the positive space‐charge density and the breakdown of the nocturnal inversion, while the conductivity shows no reduction.In Part 2 the equation relating the concentration of atmospheric small ions to their rate of production and lifetime, the electric field and the atmospheric diffusivity has been solved on a computer. The solutions obtained for various sets of conditions are compared with experimental results. Good agreement is found with observations of the space charge, and moderate agreement with those of the field and the diffusivity, but the theoretical prediction that the nucleus concentration is the most important factor influencing the smallion concentration is not supported by the observations. Some possible reasons for this are discussed.
The effect of the Curtis‐Godson approximation on the accuracy of radiative heating‐rate calculations
Authors: Walshaw C. D. , Rodgers C. D. 
Published: February 2007

AbstractSome exact heating rates are calculated for the water vapour pure rotation band, the 9·6 μ ozone band, and the 15 μ carbon‐dioxide bands, using the appropriate spectral models with Lorentz line shape to take into account line overlap and the linear dependence of line width on pressure. These ‘exact’ heating rates are then compared with those calculated under the same conditions but using the Curtis‐Godson approximation (CG). It is shown that the errors introduced by CG are always less than a few per cent for all except the 9·6 μ ozone band. The reasons for CG failure are very complex, but tentative conditions for its validity are suggested. This leads to a delineation of regions of the spectrum for which more accurate methods may need to be used.
On the mean meridional circulations in the Northern Hemisphere during the winter season
Authors: Palmén E. , Vuorela L. A. 
Published: February 2007

AbstractA new attempt is made to determine the mean meridional wind components of the Northern Hemisphere at different levels for the winter season December‐February, and to compute the mean mass circulation as a function of latitude. The computation shows the existence of a strong ‘direct’ Hadley circulation in low latitudes and a much weaker ‘indirect’ circulation in higher latitudes. From the mass circulation in low latitudes the meridional flux of water vapour is computed, and from the divergence of this flux the difference between precipitation and evaporation from the earth's surface is evaluated for different latitudinal belts between the Equator and 40°N.
The horizontal transport of heat and moisture ‐ a micrometeorological study
Authors: Rider N. E. , Philip J. R. , Bradley E. F. 
Published: February 2007

AbstractMuch micrometeorological work to date has assumed, or tried to ensure, that conditions of horizontal homogeneity exist at and near the earth's surface. The present paper reports an observational study of the variation in the meteorological elements with distance and height downwind of a pronounced discontinuity from dry to wet surface conditions. In particular the temperature and humidity fields were observed together with the changes in the radiative‐balance components and in the wind structure. It was found that temperature and humidity changes at a height of 5 cm within 16 m of the discontinuity were commonly as much as 5$C and 5 g m−3 respectively. Theoretical treatments of the problem are outlined, and a slight modification of Philip's (1959) analysis is used to compare observed and predicted changes in temperature and humidity with distance downwind up to a height of 150 cm. It is found that the observed humidity changes are in good agreement with expectations, but that the measured temperature changes are about half those predicted. Changes in the evaporation rate in various distance intervals downwind from the leading edge have been computed. These are compared with an estimate of the rate which would have occurred under the same conditions from a wet area of infinite extent.The discrepancies between theory and observation are attributed to the fact that the available theory fails to take into account the (demonstrable) differences in the aerodynamic properties of the adjacent surfaces. There is scope for further theoretical and experimental work on this matter.
A note on horizontal dispersion from an instantaneous ground source
Authors: Gee J. H. , Davies D. R. 
Published: February 2007

AbstractIn this paper the shearing advection term, proposed by Lettau (1951), is introduced into an analysis of the diffusion equation discussed recently by Saffman (1962). The case of an instantaneous point source emitted at ground level is considered when the height of diffusion can be assumed to be unlimited; in this case Saffman obtained formulae describing the position of the centroid, x, and the downstream standard deviation, σx, at ground level, of a cloud of marked particles as functions of time, this work being based on a form of analysis which was used initially by Aris in discussing longitudinal diffusion of material in laminar flow through a tube. The introduction of a shearing advection term leads to formulae, for × and σx (excluding the effect of horizontal diffusivity Kx), which predict respectively a 16 per cent and 20 per cent decrease in numerical values compared with those given by Saffman's analysis. If, in addition, eddy diffusivities which are assumed to depend linearly on time are introduced, the respective decreases caused by the shearing advection effect are 19 per cent and 25 per cent.
The height variation of vertical heat flux near the ground
Authors: Elliott W. P. 
Published: February 2007

AbstractProfiles of vertical heat flux were obtained by subtracting the component of temperature change due to long‐wave radiation flux divergence from some observed temperature changes and integrating the resultant temperature change. the method of computing the radiative component was essentially one suggested by Funk (1961). the resultant fluxes of sensible heat showed significant height variations near the ground at night but almost no variation near the ground in the day. At night the coefficient of eddy conductivity increased with height up to about 50 metres and subsequently decreased. In the daytime the concept of thermal diffusion does not appear to adequately describe the sensible heat flux.
Charge transfer associated with temperature gradients in ice crystals grown in a diffusion chamber
Authors: Latham J. 
Published: February 2007

AbstractIce needles were grown from the vapour on extremely fine quartz fibres situated inside a diffusion chamber. When temperature gradients were applied to the needles charge was separated within them; the colder end became positively charged and the warmer negatively charged. the magnitude of the charge separation was determined by measuring the deflection of the needles in a weak electric field and was in approximate agreement with Mason's equations.Measurement was made of the charge acquired by an ice needle when it was momentarily touched against a dendrite inside the diffusion chamber. When the needle was warmer than the dendrite it acquired negative charge, and when it was colder it acquired a positive charge. the magnitude of the charge transfer was explicable approximately in terms of Mason's equations.
Correlations in the vertical component of the wind at heights of 600, 1,600 and 2,600 ft at cardington
Authors: Angell J. K. 
Published: February 2007

AbstractWith the primary purpose of differentiating between various theories of convection in the planetary boundary layer, spectral and cross‐spectral analyses have been performed upon wind‐inclination data obtained at heights of 600, 1,600 and 2,600 ft at Cardington. Based upon approximately 4,500 observations at 15‐sec intervals at each of the 3 levels, the correlation between inclination angles varies from a maximum of 0·48 for oscillations of 25‐min period to a minimum of — 0·01 for oscillations of 2·5‐min period. Based upon 17 or 18 hour‐long runs, these inter‐level correlations are greater in the afternoon than in the morning and tend to increase as the wind shear between levels decreases. In general, there is no firm evidence that the oscillations occur earlier at one level than another and it is considered that the data available tend to favour the plume model of convection over the bubble model of convection.
Transpiration from short grass
Authors: Glover J. , Forsgate J. 
Published: February 2007

AbstractTranspiration from a low, closely matted perennial grass has been measured daily by a floating lysimeter, over a period which included a long natural drought. Transpiration was found to continue at a level determined by the physics of the environment until all the available moisture in the root range was exhausted. This supports Veihmeyer's hypothesis that available water is freely available to the plant between field capacity and wilting point.
Self‐charging of melting ice
Authors: Maccready P. B. , Proudfit A. 
Published: February 2007

AbstractA brief laboratory investigation was initiated to try to duplicate a phenomenon which had been repeatedly observed in certain flight measurements during the Flagstaff cumulus studies: the apparent strong negative charging of ice hydrometeors in the final stage of melting during their fall outside of the cloud. Sample ice structures of 1 cm3 from distilled water were melted in an 8 m sec−1 air stream at ambient temperatures. Regardless of the technique of measurement used (current into the sample, charge into the sample, or charge into an open Faraday cage around the sample), certain features were observed consistently: (a) a positive charge was acquired by the sample, (b) the magnitude of the charge was of the order of 30 picocoulombs (0.1 esu), and (c) the acquisition of charge occurred primarily during the later portion of the melting process. Generally similar but more erratic results were obtained with actual hail samples.The sign of the charging was opposite to that observed in the flight measurements, and the magnitude of the charging was far less, but the correlation of the charging with the final stage of melting agreed with the results of the flight tests. Careful laboratory tests previously reported by Dinger and Gunn also showed positive charging during melting, and the charging correlated with the amount of dissolved gas and hence bubbles. It is felt that the charging effect is real and is probably primarily associated with effects from bubbles during melting, and that the disagreement in sign and magnitude between the laboratory and flight measurements may be attributable to the large differences in ambient conditions and differences in the physical and chemical properties of the hydrometeors.
Exchange between water droplets and tritiated water vapour
Authors: Booker D. V. 
Published: February 2007

AbstractMeasurements have been made of the activity collected by a stream of distilled‐water droplets falling through an atmosphere saturated with tritiated water vapour. The results, combined with those of Friedman et al. (1962), confirm theoretical predictions of the rate of exchange between droplets of radius 40‐1500 microns and the surrounding vapour.