bluuebunny/crossref_metadata_2025 huggingface dataset:
A study of the deviations of wind speeds and directions from geostrophic values
Authors: Godson W. L.
Published: February 2007

From a knowledge of the three‐dimensional wind field as a function of space and time, the total wind acceleration and the trajectory curvature can be computed, permitting the evaluation of the geostrophic wind vector without recourse to analysed isobars or height contours.

A study of 618 cases at 10,000 ft for a 3‐day November sequence, using observed winds over the North American continent, revealed that the mean absolute angle between the reported wind and the geostrophic wind directions was approximately 15°. Large deviation angles were associated with low geostrophic wind speeds, and thus indirectly with low latitudes. The corresponding mean cross‐isobar wind component was slightly greater than 5 mi hr−1. The mean absolute deviation between wind and geostrophic wind speeds was of the order of 7 mi hr−1, the corresponding mean relative deviation being just under 30 per cent. Large relative deviations were associated chiefly with low geostrophic wind speeds, hence indirectly with low latitudes.

The mean total wind acceleration slightly exceeded 40 mi hr−1 day−1. The mean trajectory curvature corresponded to a radius of curvature of 175 mi. It was found that the mean components of these terms associated, formally, with horizontal and vertical advection were virtually identical in magnitude, illustrating the importance of the vertical velocity contribution to wind accelerations and curvatures. The mean local tendency component was numerically smaller than the two advective terms in the care of accelerations, but numerically larger in the case of trajectory curvatures.
The composition of coagulation‐elements in cumulonimbus
Authors: Ludlam F. H.
Published: February 2007

Calculations are made from which it appears that the rate of loss of heat from ice particles growing by coagulation in dense supercooled clouds may be insufficient to allow all the acquired water to freeze. The larger coagulation‐elements within cumulonimbus clouds may therefore have liquid skins at levels where the temperature has fallen to −20° or −30°C. The rain‐drop multiplication process envisaged by Langmuir may thus proceed also at temperatures well below 0°C, and the effect may also be important in the production of ice nuclei by‘splinter’ formation and in the generation of thunderstorm electricity.
On the theory of large‐scale vortex motion in the atmosphere
Authors: James R. W.
Published: February 2007

A consideration of the parameters best suited to characterising a circular vortex leads to the conclusion that an intensity factor, the central pressure defect (or excess) and a scale, or size factor are fundamental.

General expressions are given for the mass defect of a cyclone, its total potential energy, and the total kinetic energy of geostrophic winds. These parameters are estimated for 17 cyclones on the basis of an assumed pressure‐profile shape. It is shown that the ratio of the mean geostrophic kinetic energy to the mean potential energy is of the order 0.08.

A dimensionless measure of the‘flexure’ or bending of a pressure profile is shown to vary relatively slightly from cyclone to cyclone, suggesting that the profile shape is roughly the same for all symmetrical lows.

The kinetic energy arising from ageostrophic components of wind are also discussed and it is shown that a quasi‐geostrophic vortex in bodily movement has the same (ageostrophic) kinetic energy as a rigid body moving with the same speed and having a specified mass, the virtual mass of the vortex. It is shown that the virtual mass of a cyclone is of the same order as the total mass defect.

It is shown how elleptical vortices, troughs and wedges may be treated, and a‘front’ is shown formally to be representable as a line distribution of circular vortices.

On the basis of the models introduced, a dynamic theory of quasi‐geostrophic vortex interaction is put forward, based on the hypothesis that in mutual interaction the pressure profiles of individual vortices are conserved.

This theory leads to the conception of a potential barrier inhibiting the over‐close approach of two vortices, and permits vortex interaction to be conceived as the motion of attracting and repelling'centres of action.
The meridional eddy flux of energy
Authors: White Robert M.
Published: February 2007

An investigation of a large number of upper‐air soundings over regions of North America shows that the eddy transport of sensible heat is poleward in the mid‐latitude troposphere, reversing and becoming equatorward in the stratosphere. The eddy transport of sensible heat reaches its maximum in middle latitudes, decreasing both poleward and equatorward. It is shown wherein these results differ from those recently presented by Priestley. The transport of sensible heat has a high seasonal variation, being much stronger in winter than in summer. There are indications that at very low latitudes the eddy sensible‐heat transport is directed equatorward.

The eddy transport of latent energy is described by means of the same soundings and is found to be poleward throughout middle and high latitudes with a maximum at the ground and decreasing with altitude. The principal seasonal variation in the transport of latent energy appears to be the northward shift of the mid‐latitude maximum from winter to summer. This maximum is not very pronounced, the transport in both seasons being relatively constant through middle latitudes.
A hemispherical study of the atmospheric angular‐momentum balance
Authors: Starr V. P. , White R. M.
Published: February 2007

An attempt is made to determine the meridional eddy transport of angular momentum for the northern hemisphere in the vicinity of 30°N. latitude from upper‐wind observations for a period of six months. Two somewhat different methods of evaluation give essentially comparable results and indicate the presence of eddy transports which are ample to compensate for frictional losses of angular momentum farther north. No indications of the presence of a mean meridional circulation of the strength and character needed to produce a sensible northward transport of angular momentum are found.
Seasonal variation of the axes of low‐latitude pressure and divergence patterns over the oceans
Authors: Gordon A. H.
Published: February 2007

The seasonal fluctuations of the mean latitudes of the axes of the doldrums and sub‐tropical anticyclones over all the oceans, and of the belts of maximum convergence and divergence of surface winds over the North Atlantic are evaluated and discussed. There is a lag of about two months after the sun is vertically overhead in the positions of the axes. The seasonal movement of the axes of the sub‐tropical anticyclones is about half that of the axes of the other elements considered. In the North Atlantic and West Pacific Oceans the correlation between the mean latitudes of the axes of the doldrums and sub‐tropical anticyclones is high.
The dissipation of kinetic energy in the lowest layers of the atmosphere
Authors: Taylor R. J.
Published: February 2007

The supply of kinetic energy to a shallow layer of air is considered. The cases chosen for analysis comprise occasions of comparatively strong wind and of fairly small temperature gradient so that the supply of kinetic energy from the vertical flux of total heat is not important at small heights. In these cases the diffusive flux of kinetic energy is also shown to be negligible. Hence it follows that, on these occasions, the rate of dissipation per unit volume is given by the product of the local values of the shearing stress and vertical gradient of mean velocity when steadiness and horizontal uniformity of the turbulence are assumed. Estimates of the rate of dissipation per unit mass at heights from 1 m to 50 m are made for particular occasions and used, together with the observed energy densities, to provide estimates of the size of the dissipating eddies at the heights of observation according to expressions given by L. F. Richardson and G. I. Taylor.
The wind stress over the ocean from observations in the trades
Authors: Sheppard P. A. , Omar M. H.
Published: February 2007

The method of geostrophic departure is used to determine the surface drag of the ocean in the Trade‐wind belt, this region being particularly suitable for the technique because the opposition of the thermal wind to the surface geostrophic wind leads to a maximum in wind speed at a few hundred metres elevation. This pilot study is based on balloon winds at three very small Pacific islands and the U.S.W.B. Northern Hemisphere Charts of surface pressure. A drag coefficient of 1·0 × 10−3 is found from two of the stations, and 1·5 × 10−3 at the third and there is no systematic variation with surface‐wind speed from 3 m/sec to 12 m/sec. The higher value of drag coefficient may be due to excessive roughness caused by reefs, or possibly to thermal instability.

A similar analysis for San Juan in the West Indies shows the disturbing effect of a larger land area on the geostrophic departure so that only in high surface winds does the apparent drag tend to the probable value. Some other features of the Trade‐wind regime are briefly described.
Some downstream effects associated with large‐amplitude troughs in upper flow patterns
Authors: Smith C. V. , Forsdyke A. G.
Published: February 2007

The change in amplitude of troughs occurring downstream of a (primary) trough in the 500‐mb contour pattern over America, is examined for the four days subsequent to the first formation of the American feature.

Over the time interval considered, the association between a large‐amplitude primary and the presence, in a broad sector to the east, of a large‐amplitude downstream trough is found, in general, to be small. The association increases markedly however when a primary persists for two or three days : on a large proportion of such occasions the next downstream trough attains dimensions comparable with that of the primary. Persistence of this downstream trough would frequently appear to be directly related to persistence of the upwind (primary) trough.
The length of dry and wet periods
Authors: Longley R. W.
Published: February 2007

A study was made of the length of dry and wet spells at five Canadian cities. From the results of the study it was learned that after a wet day the probability of the following day being wet is constant no matter how long the wet period has persisted; the same is true for the weather following a dry day except that there is a slight increase in the probability of dry weather with increasing length of the dry period.

As a corollary to the study, the probability of the weather following either a wet or dry day was determined for each month for each of the five cities. Also a simpler method is suggested for determining approximations to these figures.
The duration of wet and dry spells at Moncton, New Brunswick
Authors: Cooke D. S.
Published: February 2007

It is shown that the frequency distributions of dry and wet spells at Moncton, N.B., conform very closely to geometric and logarithmic series, respectively.
Spectral line shape and its effect on atmospheric transmissions
Authors: Curtis A. R. , Goody R. M.
Published: February 2007

The detailed shape of a pressure‐broadened spectral line obtained by Lindholm has been evaluated and used to derive an expression for the mean transmission of a disordered band. This is compared with the corresponding expression using the Lorentz line shape. It is shown that the difference in mean transmission for these two line shapes is scarcely detectable spectrophotometrically in the cases of the principal telluric bands of ozone and water vapour, and probably also for carbon dioxide. It is concluded that, until more important problems have been solved, it is probably uneconomical to make use of line shapes any more complicated than that of Lorentz for computations of heating rates in the atmosphere, provided always that theory is used only in order to apply existing laboratory data to atmospheric conditions.
The partition and intensity of eddy energy at the 91‐metre level during unstable conditions as observed at Brookhaven National Laboratory
Authors: McCormick Robert A.
Published: February 2007

The magnitude and partition of eddy energy is reported for a series of observations near 91 m in which the period of averaging varied from 10 sec to 57 min. Of the 15 observations studied, 14 were made during unstable conditions typical of the predominant daytime regime found at Brookhaven in the lower 125 m. By means of moving averages as frequency filters, theree sections of the eddy‐energy spectrum are investigated. It was found that (a) the magnitude of the turbulent energy is proportional to the rate of energy supplied by the Reynolds's stresses and buoyancy forces, (b) the partition of eddy energy becomes increasingly unequal with increasing eddy size, and (c) two turbulence regimes apparently exist at 91 m with characteristics which depend on the trajectory of the air.
Short‐period variations in surface pressure and wind
Authors: Pothecary I. J. W.
Published: February 2007

Periodic variations in surface pressure and wind velocity recorded by autographic instruments on 5 July 1952 are related to wave motion along a horizontal temperature discontinuity. The wave motion is considered to have been set up when the outflow of cold air from an intense outbreak of thunderstorms over the western English Channel temporarily blocked the north‐easterly airstream beneath an inversion over southern England and the Midlands.

The oscillation was propagated upstream of the lower current and across the upper south‐easterly current for over 250 mi, with an amplitude approaching 200 m in the earlier stage.
The drag of spherical rubber balloons
Authors: Mapleson W. W.
Published: February 2007

An empirical relation Cd = 2.7 × 105 R−1 is given between drag coefficient, Ca, and Reynolds number R, for a captive, nominally spherical, rubber balloon, for the range log10 R = 5.1 to 5.8. It is suggested that the drag increases as the shape of the balloon progressively deviates from the spherical. A calibration of a Meteorological Office radiosonde windmill as a cup anemometer is also included.
Turbulence generated in standing waves
Authors: Scorer R. S.
Published: February 2007

It is shown that if standing waves occur clear‐air turbulence is to be expected at levels where there are discontinuities of shear in the airstream.
Climate, host and parasite in crop disease
Authors: Grainger John
Published: February 2007

The effects of climate on both host and parasite have been studied for two serious crop diseases of west Scotland.

First‐early Epicure potato crops in the coastal belt of Ayrshire and Wigtownshire make appreciable tuber growth before the soil temperature rises to 43°F, which is the minimum temperature of activity of the potato‐root eelworm, Heterodera rostochiensis. By the time the earliest crop is lifted early in June, cysts of the eelworm are white or yellow in colour. It is shown that such cysts make little contribution to the permanent soil infestation, thus explaining the low infestations of land consistently devoted to the growth of first‐early crops. Later lifting allows the cysts to become brown, and such cysts add considerably to the permanent soil infestation. The initial period of eelworm‐free growth on first‐earlies limits the loss in yield to 30 to 40 per cent, as compared with 80 to 100 per cent loss if the variety Epicure were planted later, at the time for a maincrop variety.

Correlation coefficients have been calculated for comparisons over eight years between the percentage of club‐root disease on swede turnips and monthly means of air and soil temperatures, bright sunshine and rainfall, for the separate months from May to October. Significant and near‐significant correlations show that a low incidence of the disease is associated with a relatively high soil temperature in July, relatively high amounts of bright sunshine in June, July and September, relatively low rainfall in September and relatively high rainfall in October.

The differential effect of soil temperature on host and parasite with potato‐root eelworm is a ‘disease‐escape’ mechanism but the effects of bright sunshine on the amount of club‐root disease are considered to be, in the present setting, an effect upon disease involving growth of the host.
Two‐way relationship between the snow or ice limit and 1,000–500 mb thicknesses in the overlying atmosphere
Authors: Lamb H. H.
Published: February 2007

Statistical studies of 1,000–500 mb thickness, (i) occurring with frozen or unfrozen forms of precipitation and (ii) prevailing at various distances from the snow or ice limit over wide regions with snow or ice cover, over bare ground and over open sea are used to discover (a) the likelihood that precipitation will take the form of rain or snow in given circumstances and (b) the behaviour of the thickness when well‐established and extensive snow or ice fields are encountered. The results indicate an important influence produced by snow fields of the order of 1,000 mi and more in longitudinal extent upon the general circulation of the atmosphere.

Choice of 1,000–500 mb thickness as an indicator rests upon its adequacy and upon its general use and availability in forecasting offices; some preliminary argument is devoted to showing that the choice is reasonable on these grounds and that the lack of refinement involved in considering thicknesses of so deep a layer is not serious.
The effects of a large island upon the trade‐wind air stream
Authors: Malkus Joanne S.
Published: February 2007

A series of four helical aircraft soundings across the island of Puerto Rico on a sea‐breeze day are analyzed and interpreted. The existence of a fairly symmetrical orographic‐convection cell with ascent over the island and compensating subsidence in a surrounding ring is established. The field of motion in the convection cell is deduced from the observations together with the theoretical work on flow over heated islands by Malkus and Stern (1953). The plausibility of the motion field is tested by construction of a moisture budget for part of the cross‐section delineated by the soundings, and the effects of the subsidence, lifting, heating and other processes imposed upon the air stream by its passage over the island are discussed, with particular emphasis upon alterations in the upward transport of water vapour and cumulus cloud structure.
The representation of the annual temperature variation over central and northern Europe by a two‐term harmonic form
Authors: Craddock J. M.
Published: February 2007

A harmonic analysis is made of the annual temperature variation at 42 stations spread over central and northern Europe, using in each case 5‐day mean temperatures averaged over a considerable number of years. It is found that the first two harmonics account for nearly all the annual variance, the residual variance being usually less than 0.4 per cent of the total. Most of this residual variance seems to be random in origin, but a small part may be due to systematic departures from the two‐term harmonic form.
Water losses from various land surfaces
Authors: Rider N. E.
Published: February 2007

An account is given of observations designed to evaluate the daily water losses from surfaces carrying crops of different size and shape which were transpiring at their potential rates. The losses were obtained by the familiar aerodynamic method, the observations being made over bare soil, brussels sprouts, peas and grass. It is shown that the differences in the water losses from the various surfaces are too large to be accounted for by likely errors in the observations or method. Typical losses for sunny days in the period May to July 1955 were: peas, 2.5 to 7.5 mm; grass, 2 to 3 mm; brussels sprouts about 4 mm.
The vertical distribution of aphids in the air and the temperature lapse rate
Authors: Johnson C. G.
Published: February 2007

Aphid density diminishes with height above the ground; the linear regression coefficient, ‐b, of log density on log height is an approximate expression of the vertical density profile. A low negative value of b suggests a relatively high degree of upward transport, and a high value the reverse.

From May to October 1948, aphid densities were estimated simultaneously at 6 heights from 50 to 2,000 ft over 2‐hr periods during the day: lapse rates to 2,000 ft were also measured. The regression coefficient, ‐b, of log density on log height was inversely correlated with the mean lapse rate between months; September and October were associated with low lapse rates and steep density gradients.

Correlation coefficients of b with lapse for 2‐hr periods were negative above a lapse of 10°F/2,000 ft, and became statistically significant in the afternoon. Below the 10° value no significant correlation existed, probably because low lapse rates occurred usually in the early morning when densities were low and factors other than atmospheric mixing could affect the profile.

Two examples of the change in the vertical profile from hour to hour throughout the day are given to illustrate the association of high lapse rates with high‐altitude dispersal and the limitation of upward transport when lapses are low: but biological factors also play a part in determining the form of the profile and these are briefly discussed.
The detection and measurement of water droplets
Authors: Liddell H. F. , Wootten N. W.
Published: February 2007

The use of a dyestuff (Naphthol Green B) in gelatine, coated on the slides of a cascade impactor, provides a method for determining the drop‐size distribution of fogs and water sprays which is easy to apply in practice and gives a permanent record for subsequent microscopic analysis. Calibration of the stain remaining after evaporation of a droplet impacting on the slide shows it to be, on the average, 2.5 times the diameter of the droplet. The method can be readily used for droplets of less than 1 μ diameter.
Integrated absorbtion by the 9.6 μ band of ozone
Authors: Walshaw C. D.
Published: February 2007

An account is given of laboratory measurements of absorption by the 9.6 μ band of ozone using dry air as the foreign gas. The experimental results for the band area, Ar, are tabulated for ozone amounts up to 1.5 cm STP and pressures from 10 to 760 mm Hg at a temperature of 20°C; the slit width is 6.5 cm−1. An empirical formula for Ar is given. The best fit is obtained with slightly modified values of the ultra‐violet absorption coefficients determined by Vigroux (1953), when the standard error in band area is 2.4 per cent.
Aircraft observations of rain and drizzle from layer clouds
Authors: Singleton F.
Published: February 2007

Aircraft observations of droplets greater than 100 μ diameter in 20 low layer clouds indicate that these drops can occur in concentrations of approximately 0·1 per litre to 10 per litre in clouds of 1,000 ft (300 m) to 7,000 ft (2,100 m) thickness. These observations are presented together with data relating the thickness and height of a further 120 layers of low cloud to their ability to produce precipitation at the ground. A diagram is shown which, it is suggested, might be of use as an objective aid for forecasting the occurrence of precipitation from low‐layer cloud.

The results are discussed qualitatively in terms of the condensation‐coalescence mechanism of droplet growth and demonstrate the efficiency of layer clouds as producers of large drops (and consequently precipitation). There is evidence that, for the range of cloud depths considered, coalescence is the predominant mechanism for drop growth for temperatures down to – 11°C to – 12°C.
The compensation of the effects of potential‐gradient variations in the measurement of the atmospheric air‐earth current
Authors: Adamson J. , Chalmers J. A.
Published: February 2007

A well‐known method of determining the atmospheric air‐earth current consists of collecting and measuring the current flowing into an insulated receiver at ground level. A difficulty encountered, however, is that any variation of the potential gradient produces a displacement of the bound charge on the collector, leading to a spurious ‘displacement’ current. In the simplest form of the method, this current can occasionally be so large as to mask completely the true‐earth current.

This article describes a development in which the sum of the air‐earth and displacement currents is measured at one terminal of a differential amplifier, while a field machine provides automatic and continuous compensation for the displacement current at the other terminal. The apparatus thus enables a continuous true recording of the air‐earth current to be made, and is an improvement on previous methods of eliminating the displacement current which necessitated intermittent recording of the integrated charge collected over a period of time. Satisfactory results are obtained with this method in all weather conditions except thunderstorms.
Some observations of drop‐size distributions in low layer clouds
Authors: Singleton F. , Smith D. J.
Published: February 2007

125 drop samples in ten layers of low cloud of thickness 700‐7,500 ft (210‐2,300 m) have been obtained using the magnesium‐oxide coated‐slide technique. These observations are discussed in terms of the condensation‐coalescence mechanism. Comparison has been made between these observations and a similar set, also obtained by the Meteorological Research Flight, Durbin (1959), for convective cloud, from which it is shown that the coalescence process is in greater evidence in the layer clouds. Values of water content deduced from the drop spectra are higher than those previously reported by other workers and correspond in magnitude to the full adiabatic values suitably modified by redistribution within the cloud.

Some measurements are also discussed relating to the effect of the aircraft on the representativeness of the drop samples. The extension of the magnesium‐oxide calibration to drops larger than 100 μ diameter has also been examined experimentally.
A report on some experiments in numerical prediction using a stream function
Authors: Knighting E. , Hinds Mavis K.
Published: February 2007

A series of experiments is described in numerical forecasting in which the wind field at mid‐tropospheric level is derived from a stream function, but the wind shear in the lower troposphere is computed in a variety of ways. The results show that the overestimation of the pressures in the region of anticyclones, which is inherent in models in which the mid‐tropospheric wind field is assumed to be geostrophic, is significantly reduced.
Some aircraft observations of fluxes of solar radiation in the atmosphere
Authors: Roach W. T.
Published: February 2007

An account is given of some recent observations of solar‐radiation fluxes from aircraft of the Meteorological Research Flight. This account consists of two parts:

High‐level measurements of the albedo of the earth and atmosphere from a Canberra aircraft over southern England in 1958 and 1959, and over the Sahara Desert and Equatorial East Africa in June 1958 and January 1960.

Observations from a Hastings aircraft of the absorption and reflection of total and visible solar radiation from a cloud‐free atmosphere over the English Channel.

From (1), frequency distributions of observations within given albedo ranges have been extracted and correlation of albedo with the observed cloud cover attempted. The mean of albedo observations over southern England was 0·5 in 1958 and 0·3 in 1959; over the Sahara Desert about 0·3 and over Equatorial Africa about 0·2.

The Hastings flights show that instantaneous heating rates in excess of 5°C/day at some level below 10,000 ft occur quite frequently. When allowance is made for heating due to absorption by the near infra‐red bands of water vapour and carbon dioxide (1‐2°C/day) it is found that the residual absorption does not depart significantly from greyness except in a few cases when the absorption appears to be concentrated in the near infra‐red.

For the lowest levels, the absorption coefficient due to haze for total radiation is estimated to average about 20 per cent and for visible radiation about 5 per cent of the attenuation coefficient. Back‐scattered radiation accounts for about 5 per cent of the total attenuation.
A three‐parameter model of the atmosphere suitable for numerical integration
Authors: Bushby F. H. , Whitelam Clare J.
Published: February 2007

Subject to various approximations, a system of five simultaneous equations (three partial differential equations and two algebraic equations) is derived to predict the height of three contour surfaces corresponding to the bottom, middle and top of the troposphere and to evaluate the two fields of vertical motion corresponding to the upper and lower halves of the troposphere. The atmospheric model used is an extension of the two‐parameter model proposed by Sawyer and Bushby (1953).

Numerical integrations have been carried out for 20 cases and the results are given in statistical form. Two forecasts are illustrated with diagrams. The accuracy is better than that obtained with the two‐parameter model, and the forecasts are of the same standard as those produced by conventional methods.
A graphical method of objective forecasting derived by statistical techniques
Authors: Freeman M. H.
Published: February 2007

The objective forecasting technique described consists of a composite diagram from which the forecast value of the predictand can be read directly, given the values of the predictors. Each section of the diagram combines a new predictor with an estimate of the predictand obtained from the previous sections. The isopleths in the diagrams are obtained by fitting a curved surface (involving powers and cross‐product terms of up to the fifth order) to the basic data by a ‘least squares’ procedure. Only terms which are significant at the 5 per cent level are retained in the regression formulae so produced. At each stage the predictor to be selected is that which contributes most to the combination so far chosen.

The method was used to forecast visibility (as one of 32 code figures) at London Airport three and six hours ahead. When it was tested on two winters' independent data, correlation coefficients of 0·89 and 0·83 were obtained for the 3‐hr and 6‐hr forecasts, respectively. During the same period the figures for the normal subjective forecasts made at London Airport were 0·87 and 0·74.
Similarity theory and temperature structure in the lower atmosphere
Authors: Panofsky H. A.
Published: February 2007

An equation based on similarity theory is used to explain the properties of various temperature statistics. Extensive observations indicate that wind and temperature profiles are nearly similar, and the ratio of the exchange coefficients for heat and momentum is of order one.
Fitting meteorological extremes by various distributions
Authors: Gringorten I. I.
Published: February 2007

Meteorologists often fit extreme values by the double‐exponential distribution, the limiting form of distributions of the exponential type. But distributions of some extremes, such as the lowest annual temperatures (1875–1960) at Washington, D.C., fall well short of the limiting form. Alternative means of fitting sets of extreme values are proposed. For data such as the highest January temperature at Washington, an extra physical phenomenon appears to restrict the magnitude of the largest values.
Radiative flux divergence in radiation fog
Authors: Funk J. P.
Published: February 2007

Radiative flux divergence (div R) recordings at heights between 1 and 11 m have been carried out before and in the initial stages of radiation fog. Temperatures, temperature gradients, radiation ground temperature, net radiation, relative humidity and wind speed were also measured.

The general pattern showed essentially either a high div R preceding fog formation (once short‐lived radiative cooling of over 30°C hr−1 was observed); or a high div R some time before, interrupted by a period of very reduced, or even negative div R (radiative warming), with resumed radiative cooling only immediately before fog formation.

It is reasoned that radiation and, to some degree, temperature phenomena during fog formation can be patchy in character and that some of the results observed on different occasions may actually happen on one and the same occasion. These and other indications suggest small‐scale advection to be important.

The results also demonstrate the important role of haze and suggest its vertical distribution rather than quantity to be the important factor.

The div R observations show the driving character of radiation and can readily explain the dissipation of latent heat of condensation and many observational facts which were difficult to interpret by conventional reasoning, such as the absence of fog under seemingly ideal conditions or the suddenness of its onset. A composite picture of radiation fog formation is given.
The effect of wind shear on horizontal spread from an instantaneous ground source
Authors: Saffman P. G.
Published: February 2007

The medium range spread of a cloud of material released in a turbulent wind is considered theoretically. Attention is directed to the effect of systematic wind shear with height to see whether this may be important. It is shown that there are two cases, according to whether the height to which the material may rise is effectively bounded or not.

In the first case when the height is bounded, the situation is in essentials the same as for flow in a pipe (Taylor 1953, 1954). After a sufficient length of time, the horizontal spread is described by a diffusivity which is the linear sum of two components, one representing the effect of horizontal turbulent fluctuations of the wind, and the other the effect of an interaction between the systematic wind shear and the vertical transport of material by the turbulence. For given mean wind profile, the latter effect is proportional in an inverse way to the coefficient of vertical diffusion.

In the second case, when the material may rise to any height, it is shown that the horizontal spread cannot be described, in general, by a constant diffusivity, and that the horizontal mean‐square spread or dispersion does not increase linearly with the time. However, the horizontal fluctuations and the interaction of wind shear with vertical transport still contribute independently to the horizontal dispersion. It is found that the interaction effect now depends in a direct way on the coefficient of vertical diffusion. It is also concluded that for medium‐range diffusion the effect of the interaction of wind shear with vertical transport is dominant.
Electrification accompanying melting of ice and snow
Authors: Matthews J. B. , Mason B. J.
Published: February 2007

Attempts to measure the electrification produced by the melting of ice and snow, known as the Dinger‐Gunn effect, have been made with three different experimental arrangements. In one of these snow crystals were grown and melted under very clean conditions inside a diffusion cloud chamber. The results of the three experiments are consistent in failing to detect a separation of charge and in indicating that any charge produced was < 10−2 e.s.u./g or two orders of magnitude smaller than reported by Dinger and Gunn. This result was unaffected by varying the purity of the ice, its air content and the rates of freezing and melting, and the pH value of the water. Accordingly, it is concluded that charging associated with the melting of snow or hail is unlikely to be an important feature in the electrification of clouds and precipitation.
The influence of cloud on hourly amounts of total solar radiation at the sea surface
Authors: Lumb F. E.
Published: February 2007

Empirical relations are found for the hourly short‐wave radiation Q received on a horizontal surface at ocean weather station Juliett (52° 30'N, 20°W), for nine categories of cloud, in the form Q = 135 fs (mw hr cm−2) where f = a + b s is the fraction of solar radiation transmitted through the atmosphere, s is the mean of the sines of the solar altitude at the beginning and end of the hour, and a, b are constants.

A comparison with a similar analysis of radiation data at station Alfa indicates that the relationships derived for Juliett are valid over a wide band of latitude, and it is shown that they can be used to estimate (within ϕ 10 per cent on most occasions) the total solar radiation received at the sea surface during 5‐day periods over the North Atlantic between 45° and 65°N.
The influence of impact velocity and ice specimen geometry on the charge transfer associated with temperature gradients in ice
Authors: Latham J. , Stow C. D.
Published: February 2007

When pure uniform ice specimens of different temperatures are brought into gentle contact for times ranging from 10−3 to 5.10−2 sec and are then separated, the charge transfer is a maximum for a contact time of about 7.5 × 10−3 sec and is in agreement with the equations of Latham and Mason (1961a). With ice of higher conductivity the maximum charge transfer occurs after smaller contact times.

For impact velocities less than about 7.5 cm sec−1 the charge transfer is in agreement with the theory but above this value the charge transfer increases linearly with impact velocity. The charge transfer is also enhanced, by as much as an order of magnitude, if the ice specimens are tapered. A tentative conclusion to be drawn from these experiments is that the value of 5 × 10−4 e.s.u., measured by Reynolds, Brook and Gourley (1957) for the charge transfer per collision between an ice crystal and a warmer artificial hailstone, which is sufficient to generate charge at a rate required by a tenable theory of thunderstorm electrification, may be explicable in terms of the temperature‐gradient effect.

When steady temperature gradients are applied to uniform specimens of pure ice the potentials developed across the ice are unaffected by the pressure to which the ice is subjected. The application of steady temperature gradients to tapered ice specimens produces potentials which are up to an order of magnitude greater than predicted theoretically.
The lobe structure of giant hailstones
Authors: Browning K. A.
Published: February 2007

Photographs of thin sections through five giant hailstones are presented to portray their bubble and crystal structures. These are interpreted to show that the hailstones grew as three‐dimensional arrays of more or less completely frozen lobes, sometimes but not always separated by regions of spongy ice characterized by radial lines of bubbles.

Some lobes contained regularly spaced hyperfine growth layers consisting of series of concentric bubble fronts a few hundred microns apart. These layers are interpreted as being due to fluctuations in growth rate associated with the tumbling of the hailstones.

The growing surfaces of the lobes were strongly convex outward. This caused successive growth layers to become convoluted or scalloped. When the surface of a whole hailstone was viewed it sometimes created the false impression that the stone was an aggregate of much smaller hailstones.

The presence of surface knobs associated with the lobes significantly enhances the efficiency of heat loss from the hailstone surface. Such an effect is important in that it reduces the proportion of unfrozen water incorporated within a rapidly growing hailstone. There is even some evidence that a giant 8 cm diameter hailstone can grow in this way without becoming appreciably spongy.
A pilot study of small‐scale wind variations in the stratosphere and mesosphere
Authors: Newell R. E. , Mahoney J. R. , Lenhard R. W.
Published: February 2007

A series of high resolution robin falling‐sphere soundings covering the altitude range from 70 to 27 km have been examined in detail. Small‐scale wind variations with height are evident throughout. From profiles of the zonal wind components the apparent amplitudes and half‐wavelengths have been tabulated and summarized for 19 cases, divided into two seasons. A data‐reduction technique which imposes variable smoothing upon the initial balloon‐position data complicates the analysis, but the existence of wind fluctuations with vertical half‐wavelengths between 300 in and a few kilometres is definitely established.

A linear theory which takes into account the effects of rotation and temperature lapse rate upon such motions is briefly discussed. It is shown that the vertical flux of energy associated with the motions may be an important energy source for the atmosphere above about 80 km. A firm estimate of the magnitude of the vertical energy flux requires further information about the periods and/or the horizontal scales of the observed motions.
A note on some measurements from aircraft of precipitation within frontal clouds
Authors: Cornford S. G.
Published: February 2007

Flights have been made within frontal clouds over southern England to investigate the distribution of precipitation in the horizontal and the vertical through the systems. Several examples are presented. It was found that there is a large variability both in time and place on all scales which makes it difficult to produce a general description. In all cases the contribution to the total rain amount from the cloud layers well above the freezing level was small and the majority came from the lowest levels. In one case all the frontal precipitation was produced in the liquid phase. Some surprisingly high values of precipitation rate were found near cloud base and have not yet been explained.
The lapse rate of temperature following an air parcel
Authors: Staley D. O.
Published: February 2007

The lapse rate of temperature following an individual air parcel is derived assuming continuity of temperature, density, motion, and non‐vertical ascent in a changing pressure field. The result differs substantially in form and sometimes in magnitude from that obtained by the usual theory in which the ascent is strictly vertical and the parcel is discontinuous. When non‐vertical ascent and continuous fields are taken into account, important terms arise when the pressure field varies rapidly with time or along the horizontal coordinates. The importance of the departure of the unsaturated parcel lapse rate from gc in the computation of vertical motion by the adiabatic method is noted.
On the interhemispheric mass circulation across the Equator
Authors: Palmén E.
Published: February 2007

The discrepancy between some recent computations of the mean meridional mass circulation across the Equator is discussed. It is shown that the most probable toroidal mass circulation across the Equator amounts to about 120.1012 g sec−1 in winter (December‐February) and to about 180.1012 g sec−1 in summer (June‐August). In winter the circulation at low altitudes is southward and in summer, northward.
Turbulent energy dissipation rates and exchange processes above a non‐homogeneous surface
Authors: Record F. A. , Cramer H. E.
Published: February 2007

Energy dissipation rates and the eddy fluxes of sensible heat, momentum, and total kinetic energy have been measured above a non‐homogeneous surface. Calculations were made from simultaneous observations of fluctuations in air temperature and the orthogonal components of wind velocity at heights of 16 m and 40 m. In all thermal stratifications, dissipation rates given by the Kolmogoroff structure function are in close agreement with direct measurements of the energy extracted from the mean flow. During stable stratification, energy losses due to work done against gravity and to the divergence of the vertical flux of turbulent kinetic energy are nearly an order of magnitude smaller than the dissipation. In unstable stratification, energy losses due to the flux divergence are of the same order as the dissipation and are approximately three times larger than the energy produced by buoyancy. Estimates of the vertical heat flux from the Obukhov structure function compare favourably with directly‐measured fluxes if the constant in the structure function is assigned a value of 0.7 in lapse conditions and a value of 1.6 in inversion conditions. The measurements also show that the ratio of the diffusivities of heat and momentum at a height of 16 m is significantly greater than unity in unstable stratification and significantly less than unity in stable stratification. Finally, the new measurements of dissipation rate are shown to be consistent with values obtained in previous studies.
Some measurements of turbulence in altocumulus clouds
Authors: Watson N. R.
Published: February 2007

The method used to measure vertical gust components from aircraft and the instrumentation for this work installed in the Canberra aircraft of the Meteorological Research Flight are described. Sections showing the vertical gust components obtained during penetrations of altocumulus cloud are presented. Root mean square values were found to be about 0·5 m sec−1 in the middle of the cloud. There appeared to be some damping of the turbulence in the top of the cloud when it was under an inversion.
Some aspects of the accretion process
Authors: Macklin W. C. , Payne G. S.
Published: February 2007

Three aspects of the ice accretion process are considered. Firstly it is shown experimentally that, as the deposit temperature is raised, the individual droplets pack more closely giving a more compact and denser deposit. Models of the freezing process are then proposed and the freezing times of the droplets calculated theoretically. These calculations show that even with low density rime deposits the deposit temperature is the prime factor in governing the freezing. Finally, the statistical nature of the accretion process is considered and the probabilities of one or more droplets arriving and interfering with the freezing and cooling of an initial droplet are deduced.
Electrification accompanying the melting of ice particles
Authors: Drake J. C.
Published: February 2007

It was observed that during the melting of small ice particles supported in a vertical wind tunnel, strong convection currents developed in the melt water. Bubbles released from the ice during melting were swept up by the currents and rapidly transferred to the surface where they burst. The separation of electric charge accompanying the bursting of the bubbles was highly dependent on the convection currents in the water. The observed charging effects are not entirely consistent with theories based on the disruption of an electric double layer. In particular, the separation of charge is considerably increased if the air contains high concentrations of CO2. It is shown that the observed values of charge separation are sufficient to account completely for the presence of the lower pocket of positive charge found below the melting level in many thunderstorms.
A theoretical study of cup and vane anemometers
Authors: Ramachandran S.
Published: February 2007

The predictions of a simplified theory of anemometers are compared with observation.

The theoretical response of cup and vane anemometers to steady and varying flows are derived analytically and by using an analogue computer.

It is found that the mean indicated windspeed can be overestimated by as much as 20 per cent and that the form of fluctuations is distorted and their amplitude considerably reduced.