bluuebunny/crossref_metadata_2025 huggingface dataset:
The influence of the 15μ carbon‐dioxide band on the atmospheric infra‐red cooling rate
Authors: Plass G. N.
Published: February 2007

The upward and downward radiation flux and cooling rate are calculated for the 15μ band of carbon dioxide. Results are obtained for three different carbon‐dioxide concentrations from the surface of the earth to 75 km, and for six frequency intervals covering the band. The infra‐red absorption measurements of Cloud (1952) are used for calculations, on a high‐speed electronic computer, by a method which takes account of the pressure and Doppler broadening, the overlapping of the spectral lines, and the variation of the intensity and half‐width of the spectral lines with temperature and pressure. The numerical integration is performed over intervals that are never larger than 1 km and average values over layers are not used. The cooling rate for the present atmospheric carbon‐dioxide concentration is greater than 1°C/day from 24 km to 70 km and is greater than 4°C/day from 38 km to 55 km. The sum of the ozone and carbon‐dioxide cooling rates is greater than 4°C/day from 33 km to 57 km and agrees reasonably well with the heating due to ozone absorption. The results for different carbon‐dioxide concentrations indicate that the average temperature at the surface of the earth would rise by 3.6°C if the carbon‐dioxide concentration were doubled and would fall by 3.8°C if the carbon‐dioxide concentration were halved, on the assumption that nothing else changed to affect the radiation balance.
A regression method for estimating time changes of elliptically distributed winds
Authors: Scott J. R.
Published: February 2007

The theory of a method, which is simple to apply, of finding regression equations for estimating time changes of wind is given. It is applied to two of the elliptical distributions found at Singapore, and its results are compared with those from two other methods. It is concluded that its use on such distributions is useful.
The zonal wind in the upper troposphere and weather at Singapore
Authors: Scott J. R.
Published: February 2007

It is postulated that a relation may exist in certain seasons between the zonal component of the wind in the upper troposphere and weather at Singapore. On examination of observations it is concluded that such an association exists and is likely to be of use in short‐range local forecasting.
An inherent precipitation mechanism in cumulus clouds
Authors: East T. W. R.
Published: February 2007

In a fair‐weather cumulus, the largest droplets, which are of 18 microns radius, grow too slowly by differential settling to become precipitation (although the time to reach raindrop size from 50 μ, for instance, would be comparatively short). Even at 18 μ their terminal speed is sufficient for growth, were it not that most of the droplets they encounter are small enough to avoid capture. Using Langmuir's collision efficiencies, the calculated time to grow from 18 to 50 μ radius is 2 hr. This time would be reduced to 12 min if the cloud sample had first ascended until there were 4 g of condensed water per kg of air, as must take place in the updraught of a cumulus congestus.

Condensation and coalescence actually occur simultaneously and the first 50 μ droplets appear at about the 6 g/kg level; this is about the level at which the first radar echo should, and does, appear. The apparent descent of the echo can be accounted for by droplet growth at lower levels. The rapid development of precipitation in cumulus can be explained thus without invoking giant nuclei or ice.

The intensity required for turbulence to be a potent coalescing agency was found to be greater by a factor ten than the intensity of turbulence deduced from aircraft measurements.
A synoptic study of west african disturbance lines
Authors: Eldridge R. H.
Published: February 2007

The paper gives an account of Disturbance Lines (D/Ls) observed on the charts of the forecasting office of the Ghana Meteorological Department at Accra in 1955. The progress of one of the larger D/Ls is shown to indicate the extensive area affected in some cases. The origins of D/Ls, their movement, distribution, and other characteristics, are described. The importance of the phenomenon in the local weather is shown by the proportion of the monthly rainfall due to D/Ls at four Ghana stations. Emphasis is placed on the nature of the D/L as a disturbance which moves through the atmosphere, transferring convective energy to other forms, notably horizontal kinetic energy, in an ordered manner.
Attenuation of swell in the north atlantic ocean
Authors: Darbyshire J.
Published: February 2007

Waves recorded in the decay area by a ship‐borne wave recorder on o.w.s. Weather Explorer are compared with estimates of waves in the generating area. By restricting attention to the wave energy contained within one‐second wave period intervals, it is possible to eliminate the effect of dispersion and to study the decrease in height due to loss of wave energy and the broadening of the wave front. While it is not possible to give an accurate assessment of the relative magnitude of these effects, the formula obtained in the case of calm conditions or following winds in the decay area is HT/H = (300/R)1/2, where R is the distance of the recording point from the centre of the generating area. This formula does not depend on wave period and following wind speed, and suggests that the effect of broadening the wave front is the more important. It has been used successfully in predicting wave heights and periods at Casablanca.
The absorption coefficient of ozone at 3021 å
Authors: Hearn A. G. , Walshaw C. D. , Wormell T. W.
Published: February 2007

A new determination of the absolute value of the absorption coefficient of ozone at 3021 Å is described. The value obtained for the decimal absorption coefficient, measured at 20°C, is 3.310 ± 0.009 (cm STP)−1. This figure is in excellent agreement with the value for this wavelength obtained by Vigroux (1953) and may be used with confidence in meteorological applications.
Wind statistics at Singapore
Authors: Scott J. R.
Published: February 2007

Statistics, computed from radar‐wind observations made at Singapore during a period of 5 1/2 years, are presented, and discussed.
Some measurements on undercutting cold air
Authors: Berson F. A.
Published: February 2007

From time series of closely‐spaced upper‐wind (pilot‐balloon) measurements in the rear of synoptic lines of wind shift and cooling, the configuration of the elevated wind‐shear layer and the strength of the flow beneath are deduced. The height of the shear layer does not rise uniformly with time, but at one stage remains constant or decreases, before resuming a sustained rise. It is demonstrated by the method of dynamic similarity that this phenomenon is broadly the counterpart of the friction head on density surges in stratified liquids.

Cumulative inflow into the advancing wedge of cold air is compared with the total mass in the cold air wedge and found to be generally in excess of this, the exceptions occurring with sea‐breezes or analogous phenomena on a larger scale (coastal fronts). In one case where sufficient observations are available, vertical velocities are computed. The excess inflow is shown to be associated with a vertical circulation involving considerable mass transfer upward across the shear zone.
Sources and sinks of radiative energy from 30 to 90 km
Authors: Murgatroyd R. J. , Goody R. M.
Published: February 2007

The absorption of solar radiation and the exchange of long‐wave terrestrial radiation are computed for the 30 to 90 km region for all latitudes using the climatological mean temperatures given by Murgatroyd (1957). Over most of the earth's surface (approximately 30° in the winter hemisphere to 60° in the summer hemisphere) there is a close approach to radiative equilibrium at all the levels considered. In the polar regions, however, there is a significant departure from radiative equilibrium with excess heating during the summer and excess cooling during the winter.
Ice‐nucleating properties of some natural mineral dusts
Authors: Mason B. J. , Maybank J.
Published: February 2007

A fairly wide range of 28 naturally‐occurring mineral dusts has been tested for ability to act as ice nuclei. 19 substances, mainly silicate minerals of the clay and mica groups, are found to be effective at −18°C; seven of these are active above −10°C. The most abundant of these is kaolinite with a threshold temperature of −9°C. 10 of the 28 substances, again mainly silicates, are found to become more efficient ice nuclei having once been involved in ice‐crystal formation, i.e. they can be pre‐activated. Thus, ice crystals grown on kaolinite nuclei, which are initially active at −9°C, when evaporated and warmed to near 0°C in a dry atmosphere, leave behind nuclei which are thereafter effective at −4°C. Particles of montmorillonite, another important constituent of some clays and initially inactive even at −25°C, may be pre‐activated to serve as ice nuclei at temperatures as high as −10°C.

It is suggested that although such particles can initially form ice crystals only at cirrus levels, when the ice crystals evaporate they may leave behind some ‘trained’ nuclei which may later seed lower clouds at temperatures only a few degrees below 0°C. On this hypothesis, the fact that efficient nuclei are occasionally more abundant at higher levels would not necessarily imply that they originate from outer space; indeed, in view of the poor nucleating properties of some meteoritic material that was tested, it appears that atmospheric ice nuclei are predominantly of terrestrial origin, with the clay minerals, particularly kaolinite, a major source.
Modification of the structure of a tropical cyclone on traversing a high plateau
Authors: Sellick N. P.
Published: February 2007

Apparent continuity is established between an Indian Ocean cyclone which reached the coast of southern Africa and a disturbance which traversed the continent from east to west. The surface structure of the disturbance is established from autographic records of its passage over the Rhodesias and Nyasaland. The pressure field is fitted to the ‘normal’ vortex of James (1950) and the upper winds observed are in fair accord. The surface observations indicate the presence of broad belts of northwest and southeast winds with a fairly abrupt transition but there is no evidence of fronts. Precipitation of the order of 50 mm per day is recorded over wide areas on several successive days. From consideration of the observed moisture content of the atmosphere it is inferred that an inflow of the order of 2 m/sec in the lowest layers is required to account for the precipitation. Elementary dynamic theory requires that such an inflow be accompanied by increasing circulation and deepening of the system. The depression, however, weakened and filled up slowly and it is shown that a reasonable allowance for turbulent and frictional losses would account for this.
The relation between Eulerian time and space spectra
Authors: Panofsky H. A. , Cramer H. E. , Rao V. R. K.
Published: February 2007

Simultaneous observations of space correlations and time correlations verify that Taylor's hypothesis x = Ut is valid for intervals up to at least 90 m, and for relative intensities of turbulence at least up to 0·26. It is also shown that, when the stratification is stable, the longitudinal scale of turbulence tends to be much larger along the flow than across it. In an unstable layer, the scale is of the same order of magnitude in all directions.
Atmospheric pollution by hydrochloric acid
Authors: Gorham Eville
Published: February 2007

Precipitation samples from urban deposit gauges in Britain exhibit a distinct positive correlation between chloride and acidity in samples of pH < 5·7. The first‐order correlation coefficients for hydrogen ions and chloride in deposits from Sheffield, and from Manchester and Salford, are shown to be highly significant, while those for hydrogen ions and sulphate are not significant. It is therefore suggested that hydrochloric acid should be considered in assessing the causes of rain acidity in urban areas.
Non‐circular normal wind distributions
Authors: Davies M.
Published: February 2007

A series expansion for computing the distribution of wind speed for non‐circular normal wind distributions is derived.

The form of the distribution is evaluated in a typical case.
The meteorology of North Greenland during the midwinter period
Authors: Hamilton R. A.
Published: February 2007

During the midwinter months the general airflow over N. Greenland is southwesterly, but near the surface of the ice sheet, which is cooled by radiation in the polar night, katabatic winds flow from the higher parts of the ice sheet towards the coast. At sheltered places on or near the coast pools of cold stagnant air collect in fine weather when the pressure gradient is weak.

Analysis of the 700 mb charts for two midwinter seasons shows that breaks in the predominantly fine weather were caused by depressions and their associated fronts which crossed the inland ice. There were about 15 disturbances per month which affected N. Greenland, but only a few of these caused precipitation. Most of the fronts were weak and the snowfall slight. During the first period of two midwinter months under consideration the only considerable fall of snow occurred when a deep depression remained almost stationary over S. Greenland for three days and drew moist air from the N. Atlantic over N. Greenland. The onset of the strong northwesterly wind on the coast after a period of calm is generally associated with the passage of a cold front.

There is normally an inversion in the lowest layers above the ice sheet and the air temperature on the inland ice varies with the wind speed and the air mass. It is estimated that the temperature difference between the bottom and top of the inversion varies from around 0°C in overcast conditions with a strong wind to around 25°C in clear and calm conditions. Warm air is sometimes carried in the southwesterly circulation over the inland ice : the highest temperature measured on the ice sheet in the midwinter months was −18°C in a warm sector, and the lowest was −66°C in fine and almost calm weather. On the coast the onset of the northwesterly wind is marked by a sudden rise of temperature and fall of humidity : when the wind falls to calm the temperature falls rapidly at first, but within 24 hours reaches a value from which it differs little during the period of several days before the next onset of the northwesterly wind.

There is a fairly close relationship between the height and intensity of drift snow, the wind speed and the visibility. Snow does not begin to drift until the wind speed reaches 10 kt; the snow drift is moderate with a visibility of about 2 km when the wind speed is 17 kt and is heavy with a visibility of about 200 m when the wind speed is 27 kt. After a spell of fine weather over N. Greenland drift snow was absent on the inland ice even with a wind speed of 21 kt. Drift snow was observed in the coastal area only after a fall of snow.

A comparison of the mean pressures and precipitation totals for the midwinter months under review with mean charts and mean monthly precipitation totals for other stations in the area for different years suggests that the two Januarys studied were normal months, but the two Decembers were abnormal.
Stratospheric temperatures over the Antarctic
Authors: Bannon J. K.
Published: February 2007

Some recent observations together with data from earlier expeditions (Court 1942, Schumacher 1955 and others) suggest that the annual variation of temperature in the stratosphere over the Antarctic is characteristically asymmetric with a steep rise of temperature in the spring. This is probably not general over the Arctic. The tropopause over the Antarctic is significantly higher than over the Arctic in their respective winters and the variability of temperature in the lower stratosphere appears to be considerably less in the same season over the Antarctic than over the Arctic.
A rate‐of‐rainfall recorder
Authors: Adkins C. J.
Published: February 2007

In certain atmospheric and geophysical studies it is desirable to have an accurate rate‐of‐rainfall recorder which can function for long periods unattended, which can respond within a few seconds to changes in rainfall and which can provide records of good time resolution. The instrument described in this paper was designed to meet these requirements.
On the influence of thickness and temperature on the ‘cut‐off’ characteristics of glass filters
Authors: Ångström A. K. , Drummond A. J.
Published: February 2007

Schott glass filters OG1, RG2 and RG8 are investigated with respect to the dependence of the lower sharp wavelength ‘cut‐off’ on filter thickness and temperature. Typical values of the main cut‐off characteristics are presented conveniently in tabular form.
The spectrum of vertical velocity near the surface
Authors: Panofsky H. A. , McCormick R. A.
Published: February 2007

Observations of a considerable number of vertical‐velocity spectra are combined to show that under near‐neutral and unstable conditions, the shape of the spectrum is essentially invariant up to heights of order 100 m, and the ‘scale’ of turbulence is proportional to height within this régime.

A semi‐empirical working hypothesis is suggested which relates the spectrum to wind speed, lapse rate, height and roughness.
The vertical distribution of atmospheric ozone over Canadian stations from umkehr observations
Authors: Mateer C. L. , Godson W. L.
Published: February 2007

The vertical distribution of ozone is estimated from umkehr observations at the Canadian ozone stations at Edmonton, Moosonee and Resolute. Average seasonal vertical distributions are presented and compared with European and Indian results. The Canadian results indicate the existence of two levels of maximum ozone density, one at about 27 km and a lower one at about 15 km. During the spring, summer and autumn seasons the higher‐level maximum is slightly more predominant than the lower. However, during the winter months, the lower‐level maximum becomes much more pronounced. As a result, there is an extremely good correlation between ozone amount between 12 and 24 km and total ozone, three‐quarters of the seasonal changes in total ozone being attributable to changes in this layer.
Thermal structure in the lower layers of anticyclones
Authors: Findlater J.
Published: February 2007

The amount of stratocumulus cloud in easterly anticyclonic airstreams over the British Isles is shown to be related to the pressure and temperature at the base of anticyclonic inversions. These two parameters are not conservative. Fluctuations occur, often in a periodic manner, as shallow but distinct cold and warm areas circulate in the lower layers of anticyclones. These cold and warm areas originate from successive pulses of cold and warm air on the flanks of anticyclones but retain their identity after the fronts separating them have decayed and been omitted from routine analyses. Approximate dimensions and forms of significant temperature patterns are deduced.
Large‐amplitude periodic lee waves in stratified fluids Pt. (1) – Non‐linear solution
Authors: Sen‐Gupta B. K.
Published: February 2007

This paper deals with a two‐dimensional train of free, internal gravity standing waves in an inviscid, incompressible, stably‐stratified fluid bounded by a rigid base and free surface. The waves are similar to those studied by R. R. Long, and are assumed to be periodic in the horizontal direction, and independent of time. The classical linearized theory has been extended by examining the wave equation with a variableL02parameter. The equation has been solved numerically, and the method of approach has been to regard the non‐linear terms as ‘perturbations’ on the main wave term which is treated in the classical linearized theory. Deviations from the linearized theory are shown to become more pronounced the larger the amplitude of the wave, as the streamlines become displaced by presence of the non‐linear terms, and the relative magnitudes of non‐linear coefficients are compared with the main terms for the cases computed. The undisturbed fluid stream is the same for all the computed wave profiles, and the amplitude has been varied from small to large to show the development of rotor regions.
Aircraft observations of the horizontal distribution of chloride particles and their relation to drop‐growth processes in clouds
Authors: Singleton F. , Durbin W. G.
Published: February 2007

Seven flights have been made measuring horizontal variations of chloride particles (masses > 10−13 g) in the neighbourhood of the British Isles. From these it is concluded that concentrations can vary from about 1,500 l−1 in unstable north‐westerly airstreams to 300 l−1 in anticyclonic air over the U.K., and 50 l−1 over the Continent in air of continental origin. Some evidence is found that concentrations can increase near windward coasts, and can, on occasion, increase with height in the lower levels of the atmosphere.

From a theoretical examination of the droplet spectra at cloud base which, on certain plausible assumptions, would result from the observed chloride particle distributions, it is concluded that these nucleus concentrations could account for the large (> 100 μ diameter) drops commonly found in cumulus and layer clouds over the United Kingdom.
Large‐amplitude periodic lee waves in stratified fluids Pt. II – Linear solution
Authors: Sen‐Gupta B. K.
Published: February 2007

By means of a transformation originally proposed by Long (1953) we obtain exact solutions for periodic wave flow of a stratified shearing fluid between rigid plane boundaries. The examples worked out are less particular than any previously published, and show a substantial decrease in wavelength when the amplitude increases once rotors have been formed even though the equations are linear.
Radiative temperature in the heat balance of natural surfaces
Authors: Monteith J. L. , Szeicz G.
Published: February 2007

A Linke‐Feussner radiometer was used to measure the radiative temperature of natural surfaces, with small errors caused by the divergence of radiative flux and by its angular variation. On typical cloudless summer days, the maximum temperature of tall crops and of open water was close to maximum air temperature; a bare soil surface exceeded air temperature by 20°C; short grass was the coldest surface at night. A linear variation of net (total) radiation with net short‐wave radiation was established for several tall crops, and the increase in long‐wave loss per unit increase of net radiation (heating coefficient) was 0·08. Daily totals of net radiation as a percentage of solar radiation income were: 37 per cent (bare soil), 41 per cent (short grass), 46 per cent (tall crop), and 53 per cent (water).

When the aerodynamic character of a crop is known, the effective resistance of the stomata to water‐vapour diffusion can be related theoretically to the difference between surface and air temperature. For rough vegetation, estimated stomatal resistance is 0·4 to 0·8 sec cm−1 and the estimated heating coefficient is almost independent of wind speed at about 0·1.
Gusts over hills (in relation to wind‐power utilization)
Authors: Frenkiel J.
Published: February 2007

Measurements of gusts over the peaks of two hills are described, and results in the form of gust variation with height and gust amplitudes are tabulated. The difference in the ratio of gust variation with height to mean velocity variation with height for the two hills may be linked with differences in the wind ratio/temperature gradient curve.
Ozone distribution and the continuum from observations in the region of the 1,043 cm−1 band
Authors: Dave J. V. , Sheppard P. A. , Walshaw C. D.
Published: February 2007

An extended series of high‐resolution observations of atmospheric emission at five frequencies in the region of the 1,043 cm−1 ozone band has been made in order to infer the vertical distribution of ozone and the behaviour of the atmospheric continuum. The latter is found to vary from day to day and seasonally, probably because of changes in the nature, amount or vertical distribution of aerosol. This variability makes it difficult to exploit, in moist, hazy atmospheres, the inherent potential of the variation of line intensity across the ozone band in the derivation of the vertical distribution of ozone. The ozone contents of three layers, surface‐600 mb, 600–300 mb, 300–100 mb are obtained from the emission at 1,053·2 cm−1 only; they are found to be generally high, probably because the ozone transmission function used was not matched to the resolution of the observations. Relative variations in the lowest layer are probably realistic.
The identification of weather conditions associated with the generation of major storm surges along the west coast of the British Isles
Authors: Sutcliffe R. C. , Lennon G. W. , Sutcliffe R. C. , Sutcliffe R. C.
Published: February 2007

The complex mechanism of storm surge generation in the Eastern Atlantic has introduced severe difficulties in attempts to establish the basis of a flood‐warning system for the west coast of the British Isles. As an interim measure, while coastal defences are being assessed in the light of the estimated probability of abnormal levels (Lennon 1963) and while research proceeds so that any consequent contingency may eventually be met, a qualitative technique has been devised which aims at an identification of weather situations which are potentially dangerous particularly for the British Channel area and for Liverpool Bay.

Major surges are found to be generated as a result of the passage, over the sea approaches to the region, of a certain type of depression which, moving at a critical speed over shallow water, can establish conditions of near‐resonance. The relevant meteorological conditions are found to be remarkably uniform and capable of definition.
Unattended long‐period evaporation recorder
Authors: Summer C. J. , Swinbank W. C.
Published: February 2007

An evaporimeter installation is described consisting of a battery‐operated long‐period recorder coupled to a supply water tank and raingauge. The supply tank is connected to a standard evaporimeter through an automatic control valve, which regulates the supply of water to replace that lost by evaporation, and disposes of excess water due to precipitation, so that evaporation in all weather conditions can be recorded. The equipment is capable of operating for periods up to 6 months unattended, the recorder having an accuracy within ± 0·01 in. water level.
Production of droplets and salt nuclei by the bursting of air‐bubble films
Authors: Day J. A.
Published: February 2007

Air bubbles which burst at the surface of a liquid give rise to an array of small bubble‐film droplets and subsequent jet drops. Both are of meteorological significance in that they are the major means by which salt particles are injected into the atmosphere.

Counts are made of the numbers of film droplets produced by bubbles of known diameter as they burst in the highly supersaturated environment of a water diffusion cloud chamber.

It is found that, (1) the number of film droplets produced is dependent on bubble size, ranging from none for 0·1 mm diameter bubbles to 300–400 for 4 mm diameter bubbles in salt water; (2) the mean number of film droplets is proportional to the one‐half power of the bubble cap area; (3) larger numbers of film droplets are produced when bubbles burst in three per cent NaCl solution than in filtered sea water, and significantly larger numbers are produced in saline than in distilled water; (4) for a particular diameter of bubble, the film‐droplet count for successive ruptures assumes a Gaussian distribution in which one standard deviation is about one‐third of the mean number.
A study of raindrop‐size distributions in the free atmosphere
Authors: Caton P. G. F.
Published: February 2007

Observations of frontal precipitation using a vertically‐looking 3.2 cm pulsed Doppler radar have been analysed to indicate the raindrop‐size distributions present below the melting band. The variations of size distribution with rainfall rate and with height are discussed. The distributions at 750 m above ground show both fewer small drops and fewer large drops than the corresponding Marshall and Palmer (1948) exponential distributions. At greater heights there are more small drops but even fewer large drops. The changes of rain‐flux and drop‐size distribution with height provide evidence in support of raindrop coalescence but, in general, indicate the absence of pronounced accretion or evaporation. Experimental relations between equivalent reflectivity factor Ze and rainfall rate R have been derived for two heights; extrapolated to ground level the relation is Ze = 285 R1.30 for continuous frontal rains of 0.1 to 5.0 mm hr−1 at Pershore. Instances of vertical air motion due to waves induced by hills have been diagnosed.
The growth of cloud droplets by coalescence
Authors: Bartlett J. T.
Published: February 2007

A simple model of a cloud in which drops of different sizes are assumed to be falling at their terminal velocities is used to study the development of drops with radii up to 40 μ by the coalescence mechanism.

It is not clear what initial distributions of drop sizes should be used in this study and therefore the development of larger drops from several different distributions which are thought to be characteristic of the early stages of various types of cumuli are compared. In this part of the paper Hocking's (1959) values of the collection efficiencies are assumed to apply. It is found that large drops develop rapidly in maritime clouds, and for clouds characteristic of continental climates it is shown that the maximum drop radius needs to be greater than about 22μ for the coalescence mechanism to be effective. There must also be an adequate supply of drops with radii between 14 and 20 μ.

The effects of small increases in the collection efficiencies which may be caused by various factors, such as turbulence or electric fields, are studied with the model using two different initial drop size distributions. It is found that the most important single parameter in determining the onset of the coalescence mechanism is the minimum drop size capable of capturing still smaller drops. Generally, a significant effect is found if the change in the collection efficiency is equivalent to increasing the radii of the interacting drops by more than about 2μ. It is suggested that any future computations or experiments to determine changes in the collection efficiencies should look for effects of this magnitude.
Some determinations of atmospheric absorption by measurement of solar radiation from aircraft and at the surface
Authors: Robinson G. D.
Published: February 2007

Measurements, on aircraft and at the ground, of the downward and upward fluxes of solar radiation and illumination in cloudless conditions are compared with computed values and with each other. The indirect estimates of absorption from surface observations are in agreement with the more direct aircraft measurements. As in previous work, measured absorption and upward scatter is considerably in excess of that computed ‐ excess by about a factor of two at heights up to 20,000 ft. The discrepancy is attributed to suspended matter.
Eddy fluxes and the biennial stratospheric oscillation
Authors: Wallace J. M. , Newell R. E.
Published: February 2007

The zonal wind together with the eddy transports of momentum and heat at low and middle latitudes in the stratosphere of the Northern Hemisphere are found to display a two year periodicity which results from a sequence of alternating weak and strong winters, where ‘weak’ and ‘strong’ refer to the intensity of the eddy circulations at middle latitudes. At levels above 30 mb, the modulations in the eddy momentum transports appear to be strong enough to account for the year to year changes in westerly momentum in the tropics.

Similarities between the stratospheric oscillation and the biennial pulse in tropospheric data suggest an interrelation between the two phenomena. The two year periodicity may not be a permanent feature of the general circulation.
A difficulty in the interpretation of certain solar radiation measurements
Authors: Hamilton R. A. , Collingbourne R. H.
Published: February 2007

Measurements of global and diffuse radiation were made at Lerwick on a number of cloudless summer days, most of them in a very clear atmosphere. Even on the clear days about 10 per cent of the global radiation appears to be absorbed, in addition to that predicted for a model atmosphere and the amount of scattered radiation is about twice the computed Rayleigh scattering. Whereas extra scattering increases with air mass as expected, the apparent absorption decreases with increasing air mass. No physical explanation of this absorption anomaly is apparent, and no reasonable adjustment to the assumed coefficients of scattering and absorption removes it. It would be removed if the sensitivity of the Kipp solarimeter were assumed to vary with the angle or intensity of the incident radiation by as much as 10 per cent over the range concerned but special tests, carried out on Kipp solarimeters at Kew, do not provide evidence to support this assumption.
On the nature of the summit areas of severe storms in Oklahoma
Authors: Roach W. T.
Published: February 2007

Photographic and radiometric records of the summit areas of severe storms in Oklahoma obtained from a U‐2 aircraft flying at an altitude of 65,000 ft (20 Km) are combined with relevant synoptic data to make some tentative deductions on the nature of the flow and temperature fields in the outflow regions of the small fraction of giant storm cells which appear to have attained some form of quasi‐steady state.

The summit area of a giant cell sometimes appears to consist of a rather smooth ‘gasometer‐shaped’ dome 5–8 nautical miles (10–15 Km) in diameter and reaching up to 20,000 ft (6 Km) above its environmental tropopause. It is suggested this dome consists mainly of air which has risen nearly adiabatically from the surface layers (after Ludlam 1963) contained within a rather thin shell of very stable air in which there is mixing between updraught air and environmental (stratospheric) air.

A general description of the distribution and heights of storm tops along a developed squall‐line is also given.
Effect of vertical wind shear on the growth of convective clouds
Authors: Rao N. S. Bhaskara , Dekate M. V.
Published: February 2007

The relationship between vertical wind shear and the vertical extent of convective clouds is examined. In order to take into consideration the movement of the cloud, a ‘Relative Top Shear’ (RTS) is defined. Radar data and upper winds at some Indian stations in different seasons have been studied and a comparison made between RTS at different levels and the maximum tops of convective clouds. The results show that deep convective cloud was confined to layers in which RTS did not exceed 10 kt/km.
Further work with the Bushby‐Timpson 10‐level model
Authors: Benwell G. R. R. , Timpson Margaret S.
Published: February 2007

Vertical smoothing of the initial height fields proved to be a crucial step in obtaining 24 hr forecasts using the 10‐level primitive equation model (Bushby and Timpson 1967) on any set of data : the particular operator used and the effects on the forecast fields are described. The latent heat effect is examined quantitatively by comparing two 24 hr forecasts, one of which included and the other excluded the contribution of the latent heat of condensation. The forecast fields obtained when a larger grid length is used, in conjunction with an appropriately lengthened time‐step, are compared with forecasts obtained from the basic grid length and time‐step and the implications arising from the increase of scale are discussed.
The exchange of momentum, mass, and heat between an artificial leaf and the airflow in a wind‐tunnel
Authors: Thom A. S.
Published: February 2007

Investigation of a proposed relationship between the skin friction part of the drag on a natural surface and a simultaneous transfer of mass or (sensible) heat led to measurements of the dimensionless transfer coefficients Cd, Cv and Ch for the exchange of (stream‐wise) momentum, mass, and heat, between a single artificial leaf and the airflow in a wind‐tunnel. It was shown that Cv, h = C0(D/v, k/v)2/3 where D, k and v are the molecular diffusivities in air of gas or vapour, heat, and momentum, and where C0 is a generalized mass or heat transfer coefficient almost independent of ϕ, the angle of incidence between the leaf and the airflow, Cd, however, made up of a bluff‐body or pressure part Cb, in addition to a molecular skin friction part Cf, depended strongly on ϕ. C0 was close to the theoretical skin friction drag coefficient at ϕ = 0 of a thin flat plate with dimensions similar to the leaf. As a general relation between the corresponding coefficients of a natural rough surface CF = βC0, where β lies between 0·1 and unity, depending on the form and inclination (ϕ) of the roughness elements, and on wind speed.

C0 was shown experimentally to be proportional to (wind speed)−1/2 in a regime of fully‐forced convection. When the evaporation from one side of the leaf was stopped, the transfer coefficient for the removal of vapour from the other side increased by about 30 per cent. An accurate form of the psychrometric constant of the leaf includes the factor (k/D)2/3, which has the value 0·90 for water vapour.
Response curves in the theory of atmospheric oscillations
Authors: Giwa F. B. A.
Published: February 2007

It is shown that response curves are characterized by several maxima and minima. With an upper boundary condition which involves total reflection of tidal energy the maximum magnifications are unbounded. With energy propagating upwards at the upper boundary the maximum magnifications are finite and decrease in value with decreasing successive resonant equivalent depths. Thus the first three maxima occur at equivalent depths equal to 9·94 km, 6·71 km, 3·4 km, with magnifications of 9,220, 10 and 1·7 respectively. A minimum magnification of 0·57 occurs at lunar semidiurnal equivalent depth (7·1 km). This is not adequate to explain the observed lunar tide.

The features of the response curve are explained through a two layer model atmosphere. It is shown that the values of magnification at small equivalent depths are critically affected by the particular boundary condition whereas at large equivalent depths magnification is insensitive to variations in the top boundary condition.
Midwinter warmings in the upper stratosphere in 1966
Authors: Labitzke Karin
Published: February 2007

Recently produced daily 5‐mb maps of the whole Northern Hemisphere for the first quarter of 1966 have revealed differences between the middle and upper stratospheric circulation – at least during certain periods over certain regions.

Stratospheric midwinter warmings at the 5‐mb level (35 km) are compared with the circulation at the 10‐mb level (30 km) and material is presented showing that major warmings occur in the upper stratosphere without being noticed at the 10‐mb level–the highest level reached regularly by radiosondes.

The need for the exploration of the levels between 30 and 60 km with higher‐reaching radiosondes and more rocketsonde data is emphasized.
Application of the technique of ionospheric drift analysis to the study of atmospheric turbulence
Authors: Paltridge G. W.
Published: February 2007

An analysis similar to that used in the study of the behaviour of ionospheric irregularities by spaced radio receivers can be performed on the output of sensors suitably spaced in a turbulent medium. A pilot experiment is described in which a 3‐channel, microwave refractometer was mounted on a 10 m tower. The three open sampling cavities were disposed at the corners of a triangle in a vertical plane parallel to the wind direction. The results are analysed to show the usefulness of the technique for giving a picture of refractive index fluctuations in terms of the average eddy size, shape, orientation and speed and direction of movement. The technique also yields a quantitative measure of the validity of Taylor's hypothesis. A 4‐channel refractometer has been built to obtain extensive 3‐dimensional results.
Rossby waves with negative equivalent depths – comments on a note by G. A. Corby
Authors: Lindzen R. S.
Published: February 2007

The results of Corby (1967) on the effect of constant angular zonal velocity on Rossby‐Haurwitz waves in a barotropic fluid layer are extended, in an approximate manner, to waves in an infinite compressible atmosphere. It is shown that the main effect of a constant zonal basic flow in the wave equation is to doppler shift the wave's frequency. However, an important non‐doppler effect enters into the lower boundary condition. The lower boundary condition determines the free oscillations' equivalent depths which now depend on the horizontal wave numbers and can be negative – consistent with Corby's results. For the atmosphere, the more negative the equivalent depths, the more tightly the oscillation is confined to the ground.
The disintegration and electrification of charged water drops falling in an electric field
Authors: Abbas M. A. , Latham J.
Published: February 2007

The spheroidal assumption employed by Taylor (1964) has been applied to a theoretical treatment of the deformation and disintegration of charged water drops falling through an electric field of strength F. Aerodynamic and hydrostatic pressure‐difference terms were incorporated into equilibrium equations from which the fields required to produce instability were determined. Values of F (Ro/T)1/2 required for disintegration were computed as a function of the applied charge Q, undistorted drop radius Ro and surface tension T. The predicted values of F (Ro/T)1/2 have been tested experimentally for positively or negatively charged water drops of Ro ranging from 0·10 to 0·17 cm falling through horizontal or vertical fields at temperatures varying from + 20 to −18°C. The agreement between theory and experiment was found to be good; the maximum discrepancy of about 3 per cent was obtained with the largest drops utilized and is probably a consequence of the oscillation factor discussed by Ausman and Brook (1967). As predicted, the field required to disintegrate a falling drop was found to be markedly dependent upon the magnitude of the charge that it carried. It is shown that the field, F, required to effect the disintegration of the great majority of charged raindrops falling through the intense electric fields of a thunderstorm can be expressed in electrostatic units to within an accuracy of 2 per cent by the equation F (Ro)1/2 = 13·6 – 8Q.

The mass loss accompanying the disintegration of falling drops was found to bear a similar relationship to the field strength as was previously observed by Latham (1965) and Matthews (1967). Measurements on suspended drops of water showed that the valués of charge and mass loss, q and δM respectively, accompanying the disintegration are close to the theoretical maxima. The close parallelism between the experimental curves of q against Q and δM against Q suggests that instability occurs over a large fraction of the surface area of the lower hemispheroid.
On wind and shear stress profiles above a change in surface roughness
Authors: Taylor P. A.
Published: February 2007

The problem of determining the distribution of velocity and shear stress in the flow above a surface with an abrupt change in roughness is considered by using the ‘mixing‐length’ theory to relate the shear stress to the velocity profile and solving the resulting system of partial differential equations numerically. The results are compared with those obtained by Panofsky and Townsend (1964) and Taylor (1967), by assuming special forms for the velocity or shear stress profiles.
A major low‐level air current near the Indian Ocean during the northern summer
Authors: Findlater J.
Published: February 2007

It is demonstrated that high‐energy flow, in the form of low‐level southerly jet streams which have been reported earlier over Kenya, is only one part of a much more extensive current of air which flows rapidly around the western half of the Indian Ocean during the northern summer. The high speeds are associated with the concentration of the cross‐equatorial airflow into the zone from longitude 38 deg E to about 55 deg E instead of being rather evenly distributed from 40 deg to 60 deg or 80 deg E as illustrated in many climatological atlases and charts of mean flow during the season. The high‐speed current is shown to flow intermittently from the vicinity of Mauritius through Madagascar, Kenya, eastern Ethiopia, Somalia and thence across the Indian Ocean to the west coast of India and beyond. The stream is occasionally reinforced by northward flow through the Mozambique Channel.

The high‐speed air current, or system of low‐level jet streams, is closely associated with the Intertropical Convergence Zone over the Arabian Sea and western India, and variations in the strength of the stream over Kenya during a two month period were related to the rainfall which western India received from the south‐west monsoon.
Numerical experiments on the formation of a tornado funnel under an intensifying vortex
Authors: Wippermann F. , Berkofsky L. , Szillinsky A.
Published: February 2007

A tornado‐like vortex, which intensifies with time, is imposed on the upper boundary of the boundary layer. The downward development of this axisymmetric vortex is studied by numerical integration of the flow equations. The contour of the visible tornado funnel has been computed for various times. The streamlines, the field of pressure deviation, and of the tangential velocity are presented for a time close to the steady state. The influence of a varying eddy diffusion coefficient is investigated.
Fall velocities of plate‐like and columnar ice crystals
Authors: Jayaweera K. O. L. F. , Cottis R. E.
Published: February 2007

The Reynolds number of cylinders and discs falling in a viscous liquid was determined experimentally for values of the Best number (the product of the drag coefficient and the square of the Reynolds number) ranging from 1 to 104. The results were used to calculate the terminal velocities of plate‐like and columnar ice crystals.
A comparison between laboratory and atmospheric density currents
Authors: Simpson J. E.
Published: February 2007

Some known results on density currents in liquids are discussed, and the geometry of the frontal regions and of the upcurrents in the region ahead of them is shown to be similar to that of some thunderstorm outflows and sea‐breeze fronts. The detailed structure of the frontal region of laboratory density flows is described. An internal Froude number has about the same value in the model and in the atmosphere.
Temperature measurements in ships
Authors: Edwards Pamela
Published: February 2007

This note draws attention to the differences between temperatures measured in screens and by aspirated psychrometers in Ocean Weather Ships and oceanographic research ships.