bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synoptic applications of the frontal contour chart the motion of selected lows‐5–7 november 1946
Authors: Crocker A. M. 
Published: February 2007

AbstractThe formation of isolated domes of cold air in the atmosphere is described in terms of the motion of the frontal contours which delineate the topography of the upper boundaries of cold air masses. The surface synoptic chart of 5 November 1946 for North America is discussed and interpreted in the light of the frontal contour chart with special reference to the characteristics of an isolated cold dome. The subsequent development of an independent surface low on 6 November is discussed, and its motion is shown to be controlled by the movement of the cold dome. In conclusion, the advantages of the frontal contour chart in surface map analysis and in the interpretation of the three‐dimensional state of the atmosphere are emphasized.
The angular deviation of the wind from the isobars, at liverpool
Authors: Bannon J. K. 
Published: February 2007

AbstractAn attempt has been made to measure the angle between wind direction and isobar at three heights, 3,000 ft, 700 mb (10,000 ft approximately), and 500 mb (18,000 ft approximately), at six‐hourly intervals, above Liverpool, during January and February 1946. On many occasions the isobars (or contours of an isobaric surface) were not sufficiently well defined to permit of measurement, on others, wind observations were not available; in all, the following number of measurements were made:— 3,000 ft 119 700 mb 167 500 mb 186The isobars or contours were drawn, in each case, without reference to any wind observations.The accuracy of determination of the direction of the wind and of the isobars was considered in each case, and though the exact accuracy is in some doubt, it is considered that many of the deviations of the wind direction from the isobars which were found, were significant. The means of these deviations were (reckoned positive across the isobar from high to low pressure):— At 3,000 ft 7° 700 mb 1.5° 500 mb 0.1°The deviations measured at 3,000 ft were probably not typical, for it seems likely that, even at 3,000 ft the mountains have an appreciable effect on the wind direction. Analysis of the deviations showed no correlation with the stability of the air.An attempt was made to correlate the deviations at 700 and 500 mb with the general weather situation and development with some apparent success. It was found that, at both levels, there was a negative deviation on the boundary of an anticyclone, i.e. inflow to the anticyclone. Also, that at 500 mb and less markedly at 700 mb, deviations were positive ahead of a trough in the upper air, to the top of the wedge, and negative behind the trough. On one occasion the observed deviations agreed with general expectations from significant features of the general situation.The geostrophic wind was also measured at 3,000 ft, from the surface isobars, due allowance being made for height and excluding all cases of marked horizontal temperature gradients in the vicinity. The mean value of the moduli of the vector deviations of the wind from the geostrophic was found to be 9.1 kt, and the root mean.
Effect of dust and haze on measurements of atmospheric ozone made with dobson's spectrophotometer
Authors: Ramanathan K. R. , Karandikar R. V. 
Published: February 2007

AbstractTo obtain the amounts of atmospheric ozone from measurements with Dobson's photo‐electric spectrophotometer, allowance has to be made for the extinction of light by scattering due to molecules and large particles. Dobson has proposed two slightly different formulae which lead to appreciably differing values on hazy days. The assumptions involved in the formulae are examined and Dobson's equation is generalized, assuming the particle scattering to vary as λ‐n. The expression for the ozone amount is split up into two terms, the first main term being that obtained on the assumption of a pure atmosphere and the second correction term denoting the haze‐scattering. On calculating the ozone amounts with different values of n, it is found that these show much greater consistency if n has a value intermediate between those assumed in Dobson's two formulae and somewhere near zero.On hazy days in winter, it is observed that (λ‐n), the differential haze‐scattering for the long wavelengths 3300A and 4450A, is positive and its magnitude increases with increase in the haziness of the sky. This is similar to what is observed in Europe. But on most hazy days in the pre‐monsoon hot season in North India, (λ–n) is found to be negative, which means that the apparent extinction of light at 3300A is less than that at 4450A.One possible explanation is that with certain sizes of particles of given refractive index, the extinction by scattering increases with increase in wavelength as was found from observations by Götz in Switzerland and by Stratton and Houghton in U.S.A. An alternative explanation is that Dobson's instrument analyzes not only the transmitted radiation from the sun but also some scattered radiation from the surrounding hazy sky. It is probable that the North Indian summer haze scatters in the forward direction an appreciable amount of radiation which is richer in shorter wavelengths than the directly transmitted sunlight.For calculating the daily values of ozone, it is proposed to assume the particle scattering to be nearly neutral and thus varying as λ−n with n=o. The correction term in the generalized formula then becomes 0.165 (δ′–δ″) and is obtained from observations on the long wavelengths.
The size distribution of raindrops
Authors: Best A. C. 
Published: February 2007

AbstractExperimental data relating to drop size distribution in rain are examined and it is shown that in many cases the size distribution is in accordance with the following formulae 1 ‐ F = exp [‐(x/a)n] a = A Ip W = C Ir where F = fraction of liquid water in the air comprised by drops with diameter less than x. I = rate of precipitation. W = amount of liquid water per unit volume of air. A, C, p, r and n are constants. If × is measured in mm, I in mm/hr and W in mm3/m3 the mean values of A, C, p, r and n are 1.30, 67, 0.232, 0.846 and 2.25 respectively. There may be appreciable variations from these mean values, particularly in the case of n, if the precipitation is essentially of a showery or orographic nature. Tables based on these formulae are given showing values of W and of the number and total volume of drops between certain diameter limits for various rates of rainfall.
The nature of ice‐forming nuclei in the atmosphere
Authors: Mason B. J. 
Published: February 2007

AbstractDuring the last decade many experiments have been designed to investigate the initial processes of ice formation in the atmosphere. The results of these experiments are examined for clues as to the identity of the responsible nuclei and the following tentative conclusions are reached: (a) The nuclei which cause freezing between 0°C and −32°C are mainly solid, insoluble particles which are wetted by water and produce ice particles through the freezing of water drops.(b) The nuclei which become operative in the range −32° to −11°C consist of droplets of sea salt solution, ice and salt crystallising out on contaminating foreign particles at a temperature depending on the efficiency of these particles and the rate of expansion of the ambient air.(c) The nuclei effective at just below −41°C consist of droplets of pure salt solution and possibly of “ gaseous” nuclei formed industrially or by the action of ultra‐violet light on the gases of the upper atmosphere.
The effect on observations of the sky/sea brightness ratio produced by the use of colour filters and Polaroid screens
Authors: Barber D. R. 
Published: February 2007

AbstractVisual and photographic observations of the illumination of the sky‐sea horizon, made in light of different wavelengths, indicate an enhanced brightness contrast when the shorter wavelengths are excluded. The effect is most pronounced in the presence of haze, or light mist. When use is made of an analysing filter to modify the relative amounts of polarised light received from sky and sea, the degree of contrast obtainable depends on a number of independent factors, e.g., amount of cloud cover, and state of sea surface that may, or may not, combine to give better visibility of the sky‐sea boundary. Anomalous polarisation effects are frequently observed during early twilight along the anti‐solar path. This work was carried out while with the Kodak Research Laboratories. The paper is issued as Communication No. 1263H from the Kodak Research Laboratories.
The application of the similarity theory of turbulence to atmospheric diffusion
Authors: Batchelor G. K. 
Published: February 2007

AbstractThe purpose of this paper is to draw the attention of meteorologists to the potential usefulness of the similarity theory of the small‐scale structure of turbulent motion first put forward by Kolmogoroff. An outline of the theory is given first and the possibility of its application to atmospheric and oceanic turbulence is considered. As an example of its use, the theory is applied to the problem of the relative diffusion of neighbouring particles moving with the fluid, and predictions about the rate of increase of mean square distance between the particles are made. Some data obtained recently by Durst are compared with these predictions by Charnock, and similar observations made by Richardson and Stommel are considered herein. The empirical proportionality between the diffusion coefficient and the 4/3 power of the scale of observation, obtained many years ago by Richardson, is shown to be in general agreement with the theory.
Variations in thunderstorm severity in Great Britain
Authors: Forrest J. S. 
Published: February 2007

AbstractThe paper gives an account of variations in thunderstorm severity in Great Britain based on statistics of breakdowns caused by lightning on the Grid system during the 14‐year period 1934 ‐ 1947. Data are given for the seasonal and diurnal variations and for the fluctuations from year to year. The breakdown data are compared with the corresponding statistics of thunderstorm‐days, and it is shown that the thunderstorm‐day observations, if used directly, do not give an adequate indication of storm severity. It is proposed to introduce a “severity index” (s) such that the severity is proportional to Ts, where T is the number of thunderstorm‐days. For the data examined, s has values of 1.4 and 1.9.
The origin of the electric charge on rain
Authors: Chalmers J. Alan 
Published: February 2007

AbstractThe charges on rain, as measured by Simpson and by Hutchinson and Chalmers, during periods when point discharge occurs, can be accounted for quantitatively on reasonable assumptions in terms of the process of ion capture. The results show that the separation of charge must operate at levels down to about 800 m, and the consequences of this are discussed in relation to theories of the process of separation of charge.
On the diurnal variation of precipitation, particularly over central U.S.A., and its relation to large‐scale orographic circulation systems
Authors: Bleeker W. , Andre M. J. 
Published: February 2007

AbstractThe diurnal variation of precipitation is discussed and attention is drawn to the high frequency of night‐time rains over central U.S.A. A new theory for explaining this nocturnal maximum and the relatively low activity of precipitation in daytime is proposed by suggesting that cooling and heating processes during the night and the day set up a large‐scale circulation system east of the Rocky Mountains. The existence of this circulation system is proved by computation of the changes which occur in the convergence‐divergence field at 4,000, 10,000 and 18,000 ft in the free atmosphere.
The Bellani spherical pyranometer or radiation integrator; the calibration of an improved model, and some suggestions for further improvements
Authors: Gunn D. L. , Yeo Douglas , Ovey C. D. 
Published: February 2007

AbstractThe need for instruments to measure solar radiation for biological purposes has been cogently argued by Buxton but no entirely suitable instrument has been available. The radiation integrator of the Bellani type has been greatly improved by modern techniques and, with certain further suggested improvements, might become a generally useful instrument. Field calibration of the most recent model gives a mean thermal efficiency of about 75 per cent., which is much higher than that of any previous model. Of the losses, 10 per cent. is invariable and irremediable, being largely due to the glass envelope, while most of the remainder is variable and due to re‐radiation from the black receiver. Suggestions are made for increasing efficiency still more and reducing variability.
The production of showers by the coalescence of cloud droplets
Authors: Ludlam F. H. 
Published: February 2007

AbstractThe growth of unusually large cloud droplets by coalescence within isolated convective clouds is examined. It is found that if their initial radii are about 20 μ or more then growth into raindrops may readily occur. Raindrop nuclei of this size may be provided by spray in maritime air masses, but there is reason to suppose that in continental air masses droplets of the required initial size are not naturally introduced into the bases of convective clouds. Therefore the coalescence mechanism of precipitation release is probably effective only in maritime air masses. A condition for the production of a shower by the coalescence mechanism is obtained and applied to predict a minimum critical cloud depth of about 1.1/2 to 2 km. Showers may develop from clouds wholly below the 0°C isotherm if their base temperature exceeds about 8°C. A relation between the size of raindrops and the speed of the convective updraught is found, and an association is discovered between the non‐fulfilment of conditions for raindrop‐splitting within cloud and the absence of thunder.
Point‐discharge currents and the earth's electric field
Authors: Hutchinson W. C. A. 
Published: February 2007

AbstractAn account is given of measurements of the current flowing to earth through a point set up at a height of 12 m, together with the electric field near the ground. Point‐discharge current of either sign may be represented approximately as increasing with the square of the field, as found by Whipple and Scrase. In the light of recent work on corona discharges between a point and a plane in air at atmospheric pressure it is suggested that for high fields the point‐discharge current will vary directly as the field. Irregularities in the curves relating averages of discharge current and field are attributed to space charge arising from local point discharge at or near the raised apparatus used for measuring the field. An advancement of field changes ahead of the corresponding point‐current changes is considered to be an example of the reversal, by space charges, of the sign of field between the level of a raised point and the ground, described by Lutz.
The heat economy of a rimed cylinder
Authors: Ludlam F. H. 
Published: February 2007

AbstractA method is described for calculating the surface temperature of a slender cylinder which is moved through a supercooled cloud and becomes covered with rime ice. When the surface temperature reaches 0°C the ice formation proceeds at the maximum possible rate; the associated liquid‐water content of the cloud is calculated and found to be usually less than the maximum theoretical value inside a deep cumulus cloud. The rotating‐cylinder technique of determining water content and drop‐size distribution cannot therefore be used without consideration of the heat economy, and may otherwise lead to large underestimates of water concentration in severe icing conditions.
A statistical model for water‐vapour absorption
Authors: Goody R. M. 
Published: February 2007

AbstractA statistical model of a water‐vapour absorption band is discussed, and comparison with computations made by Cowling shows that it provides a very accurate account of the average transmission over narrow frequency bands. The model can be used to compute the atmospheric transmission by water vapour under conditions of meteorological importance which were not treated by Cowling.
The evaporation of raindrops
Authors: Best A. C. 
Published: February 2007

AbstractThe evaporation of a single drop of water as it falls through an atmosphere in which the lapse rate is 6·5°C/km and the surface temperature either 15°C or 41°C is examined. By making certain justified assumptions, it is shown that the change in surface area of a large drop (i.e., with radius exceeding 0·15 mm) as it falls from height z1 to z2 is proportional to (1 — f)1·13 exp (— lz) where 100 f is the relative humidity and l is a constant. Values are given for the constant of proportionality and for l. If the drop has a radius less than 0·15 mm the change in volume of the drop is proportional to (1 — f)1·062 exp (— lz).These results are then used to assess the effect of evaporation on the size and size distribution of raindrops falling through a constant atmosphere. It is shown that if the size distribution of raindrops at some initial height is given by 1 — F = exp [ — (2a/b)n] where F is the fraction of liquid water comprised by drops with radius less than a, and b and n are constants, then evaporation will lead to a change in the values of b and n but will not affect the general validity of the formula. As the rain falls through the non‐saturated air the distributive index n tends to a value between 3·5 and 4·0 whether it was greater or less than such a value initially. If the initial value of n is less than 3·0 the scale diameter b increases as a result of evaporation. If the initial value of n exceeds about 3·5 the scale diameter decreases. The effect of evaporation upon the radar response from falling rain is also examined.In the last part of the paper the effect of the evaporation of rain into air which is initially unsaturated is considered. It is shown that the air temperature tends to a steady value and the relative humidity to 100 per cent. The excess of temperature above the steady‐state value and the deficit of relative humidity below 100 per cent decrease exponentially to zero with time. The depression of the steady‐state temperature below the initial temperature is a function only of the initial temperature and relative humidity and a table is given showing the value of the steady‐state temperature for nine different sets of initial conditions. The rate at which the final state is approached depends however only upon the rate of rainfall and a formula is derived for this dependence.
Some further aspects of night cooling under clear skies
Authors: Saunders W. E. 
Published: February 2007

AbstractThe nature and cause of the evening temperature discontinuity near the ground is discussed, evidence being given that this is a result of the commencement of dew formation. Regression equations for forecasting the temperature of discontinuity are given. Methods of forecasting the subsequent cooling are discussed, and a detailed procedure given for Northolt. The relation between screen and grass minimum temperatures is briefly discussed.
A note on an intertropical discontinuity
Authors: Scott J. R. 
Published: February 2007

AbstractThe existence of a line or zone in which air flow has zero vorticity is inferred from the equation of motion. This zone is called the Intertropical Discontinuity. The detection, development and movement of this zone are discussed. It is shown how knowledge of its location and properties might be of value to forecasting near the equator.
On the theory of large‐scale disturbances in a two‐dimensional baroclinic equivalent of the atmosphere
Authors: Thompson P. D. 
Published: February 2007

AbstractThe equations of non‐viscous, adiabatic flow have been reformulated to apply to a two‐dimensional equivalent of a three‐dimensional baroclinic fluid. The state of this ‘equivalent‐baroclinic’ fluid is to be identified with conditions at a definable ‘level of equivalence’ in the true atmosphere. The two equations of equivalent‐baroclinic flow, in which neither vertical motions nor vertical dependence enter explicitly, involve only two dependent variables ‐ the temperature and height of an isobaric surface. Since those equations form a closed system, they constitute a mathematically complete theory of the development and movement of large‐scale disturbances at the level of equivalence. The stability criterion for a special type of flow, previously studied by Fjörtoft and others, has been derived from the theory and compared with Fjörtoft's earlier results. This comparison shows that the stability characteristics of three‐dimensional baroclinic flow are reproduced in two‐dimensional equivalent‐baroclinic flow, and, accordingly, that the present theory allows for the development of disturbances once they are initiated. An iterative scheme, based on successive calculations of the temperature and height tendencies, has been proposed for solving the general non‐linear equations of equivalent‐baroclinic flow. This method provides the basis for a new technique of numerical weather prediction.
Theory of airflow over mountains: II ‐ The flow over a ridge
Authors: Scorer R. S. 
Published: February 2007

AbstractThree kinds of flow over unlevel ground are defined according to their scale ‐ aerodynamic, barostromatic, and geostrophic flow ‐ and it is seen that the practical difficulties in the way of obtaining the correct value of the relevant non‐dimensional numbers in model experiments are almost prohibitive.The flow over a ridge with varying degrees of static stability is calculated, and the vertical displacement is seen to depend very much on the details of the airstream. When the flow is oblique to the ridge the air is permanently displaced sideways from its original path; and if the original airstream contains shear, shear in almost any direction may appear over a ridge. This may be displayed in billow‐cloud formations.Diurnal variations in the length of lee waves are due to the development and disappearance of an adiabatic layer at the ground. The flow is calculated in a particular case and the temperatures recorded by radiosonde balloons are shown to contain spurious inversions as the balloon passes through the waves.The disappearance of the adiabatic layer at the ground makes orographic effects a maximum around sunset on sunny days; and the appearance of a statically neutral layer in middle levels, for instance by condensation, renders steady laminar flow impossible.