bluuebunny/crossref_metadata_2025 huggingface dataset:
The calculation of a sea‐breeze circulation in terms of the differential heating across the coastline
Authors: Pearce R. P.
Published: February 2007

A method is derived for calculating the velocity, temperature and pressure distributions of the sea‐breeze produced when an initially isothermal and static atmosphere is heated differentially across a long straight coastline. Heat is assumed to be distributed vertically from the land surface by convection currents; internal friction is included but surface drag is taken as zero. The motion is separated into two parts, a rotational non‐divergent component near the coast and a mainly irrotational large‐scale tidal motion transferring mass from land to sea. The former is considered first and a numerical method devised to enable the non‐linear equations to be solved. The solutions are given as a set of diagrams each showing values of velocity, temperature and pressure calculated over a network of points, and each referring to a particular time in the development of the motion. In Section 5 the tidal motion is considered and an analytical solution obtained since the equations can be linearized. The rotational solution represents the spread inland of a tongue of cold air; well inland the wind rises some hours after heating has started, and is accompanied by a fall in temperature. An upper return current occurs in all the diagrams as well as subsidence over the sea and upper cooling inland. The vertical temperature profiles show a sharpening of the discontinuity in lapse rate at the top of the convection layer produced by the vertical velocity component. Conditions for convective instability are found to be produced dynamically in a shallow layer of the upper return current. Comments are made on the formation of ‘heat lows’ and ‘cold highs’ over continents.
Synoptic evidence for a direct circulation about a jet stream
Authors: Lee R.
Published: February 2007

The examination of a uniformly‐sloping tropopause surface during the eastward progression of a jet‐stream maximum reveals that the observed perturbation of the tropopause can be interpreted in terms of the vertical branch of a direct circulation occurring above a jet stream in the entrance region. Indirect evidence is also obtained for the existence of a corresponding direct circulation below the jet stream.
24‐hr tendencies and weather trends at Singapore
Authors: Scott J. R.
Published: February 2007

Rainfall over Singapore, on each day for a year, was compared with that of the preceding day and the day was classified according to the change of weather which had occurred. A 24‐hr tendency parameter, available on the previous day, was computed. A relation between the parameter and weather trends is demonstrated.
Radar observations of showers suggesting a coalescence mechanism
Authors: Feteris P. J. , Mason B. J.
Published: February 2007

Radar evidence suggesting the production of showers by the coalescence process is presented. On 13 days during the summer of 1955, 48 separate echoes were observed to originate below the −2°C level and 26 of these remained there during the whole life of the shower. These echoes, which were often associated with mixed formations of cumulus and stratocumulus cloud, sometimes extended above the 0°C level at their maximum state of development, but surpassed the −8°C level on only one occasion. Some of the limitations of using radar alone in this type of study are discussed.
A wind analysis for the northern Irish Sea
Authors: Reynolds G.
Published: February 2007

This paper presents frequency distributions of winds recorded at five stations in the northern Irish Sea, Holyhead, Point of Ayre, Liverpool (Bidston), Southport and Fleetwood, particular stress being laid on the strong or gale‐force winds. Figures are published which may be used for estimating the highest hourly wind speed and maximum gust to be expected in a given number of years. The direction and time of these extreme winds are discussed. The frequencies of winds of different speeds are tabulated; the frequncies of gales and winds in excess of 40 kt are examined in detail.

The relationships between the direction and strength of the geostrophic, gradient and surface wind over the area have been closely examined. It is found that neigther the geostrophic nor the gradient winds can be used to provide quantitative estimates of the surface winds either in speed or direction, on specific occasions, nor in the surface wind at one station closely related to the surface wind at another.

The variation of wind speed throughout the year is indicated.
The measurement and interpretation of near‐surface sea‐temperature profiles
Authors: Houghton D. M.
Published: February 2007

Preliminary measurements of the temperature distribution in the topmost three metres of the open ocean have been made from an Ocean Weather Ship. The two profiles recorded are discussed in relation to the important problem of heat transfer near the sea surface.
The hydrogen content of atmospheric air at ground level
Authors: Glueckauf E. , Kitt G. P.
Published: February 2007

A method is described for the separation and determination of hydrogen in air samples of approximately 200 litres N.T.P. by volume. The hydrogen is fractionally distilled from the bulk of the sample, oxidized to water by passing over heated copper oxide and finally condensed in a trap cooled in liquid oxygen. After freeing from the contaminating gases by pumping, the water is released from the trap and measured as vapour in a small calibrated volume.

Although the accuracy of the method in its present form is not better than ± 10 per cent, the results seem to indicate that the hydrogen content of atmospheric air is a varying quantity.

The average hydrogen content of air at ground level is 0.6 parts per million.
Exact reflectance under a cardioidal luminance distribution
Authors: Preisendorfer R. W.
Published: February 2007

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

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

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

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

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

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

A distillation instrument for the integration of radiation, described by Bellani in 1836, rebuilt in modern materials by Gunn, Kirk and Waterhouse (1945), has a thermal efficiency of over 75 per cent. The improved instrument, mounted at ground level in East Africa, with the condenser underground in constant cool conditions, had a performance that justified manufacture. Comparisons of the manufactured instruments with a Kipp solarimeter gave high linear correlations. These results show the distillation instruments, when so calibrated, to be useful for field estimations of solar radiation. Their cost is low and the daily estimate of total radiation is quickly obtained from a simple burette reading.

Ten years' data for these Gunn‐Bellani integrators are compared with those from 4 ft diameter open water pans. A mounting is described for these pans in shallow revetted pits where their sides are shielded from the sun and are insulated from the soil by an air space. A linear correlation based on 164 ten‐day means accounts for 85 per cent of the variability. It appears that in the high‐altitude tropics this radiation integrator by itself can give the basic data for adequate estimate of water use by vegetation, and for control of irrigation.
Spectroscopic observations of the water‐vapour content of the stratosphere
Authors: Houghton J. T. , Seeley J. S.
Published: February 2007

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

A calculation has been made of the meridional circulation sufficient to transport heat between the radiational sources and sinks in the stratosphere (15‐55 km) and mesosphere (55‐80 km). Assuming that the principal heat sources are in the region of the equatorial tropopause and in the mesosphere over the summer pole, with the corresponding heat sinks near the polar tropopause and over the winter pole in the mesosphere, the main circulation patterns are found. Below 30 km there is rising air over the equator with outflow towards both poles and descent towards the tropopause in high latitudes in both hemispheres. At higher levels there is ascent over the summer pole and descent over the winter pole with a well defined flow towards the winter pole above 50 km and a more indeterminate flow pattern between 30 and 50 km. The order of magnitude of the speed of these circulations is m sec−1 horizontally and cm sec−1 vertically.

The calculations were made for the solstices, equinoxes and mid‐times between them and several particle trajectories were determined. The results are in agreement with many of the observed physical features of the stratosphere and mesosphere, particularly the distribution of tracer elements.
A Markov chain model for daily rainfall occurrence at Tel Aviv
Authors: Gabriel K. R. , Neumann J.
Published: February 2007

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

Diffusiophoresis is the name of the phenomenon whereby particles of an aerosol, through which a vapour or gas is diffusing, experience a force which moves them in the direction of the diffusive flux of the vapour or gas. Experiments are described which show that the velocity (cm sec−1) imposed on sub‐micron particles (0·01 to 0·1 μ radius) in the case of water vapour diffusing in air, when the water‐vapour pressure is small compared with the total pressure, is governed by the equation: where dp/dx is the water vapour pressure gradient expressed in millibars per cm. This result is shown to be in excellent agreement with theoretical considerations.

The absolute efficiency of diffusiophoresis in scavenging radioactive fallout particles from the atmosphere, because of cloud droplets growing by condensation, is deduced to be low. This is confirmed by a cloud‐chamber experiment in which inactive salt droplets were grown in the atmosphere of a radioactive aerosol.

Furthermore, it is concluded that the wash‐out due to diffusiophoresis accounts for less than one per cent of the total observed wash‐out of nuclear‐bomb debris for each condensation cycle occurring in nature. Cloud droplets would have to undergo over one hundred condensation‐evaporation cycles on the same condensation nucleus for diffusiophoresis to be responsible for most of the observed wash‐out.
The determination of eddy diffusivity from measurements of turbulent energy
Authors: Pasquill F.
Published: February 2007

Two existing methods of deriving eddy diffusivity from measurements of turbulent energy are briefly reviewed, one based on the theory of the inertial sub‐range and therefore concerned with high‐frequency energy, the other purely empirical and concerned with total energy. A third method, based on the statistical theory of diffusion of particles and concerned with low‐frequency energy, is suggested.

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

In Part 1 observations of the positive and negative small ions in the lowest 2 m of the atmosphere near Cambridge are described, showing that the conductivity decreases with height in this region under most conditions. Simultaneous observations of the space‐charge density are incompatible with the theory that the convection current is small compared with the conduction current, and are supported by observations of the vertical electric field. Estimates of the size of the convection current and the vertical distribution of space charge have been made.

Observations at the time of the ‘sunrise effect’ show that the increase in the field is associated with an increase in the positive space‐charge density and the breakdown of the nocturnal inversion, while the conductivity shows no reduction.

In Part 2 the equation relating the concentration of atmospheric small ions to their rate of production and lifetime, the electric field and the atmospheric diffusivity has been solved on a computer. The solutions obtained for various sets of conditions are compared with experimental results. Good agreement is found with observations of the space charge, and moderate agreement with those of the field and the diffusivity, but the theoretical prediction that the nucleus concentration is the most important factor influencing the smallion concentration is not supported by the observations. Some possible reasons for this are discussed.
The effect of the Curtis‐Godson approximation on the accuracy of radiative heating‐rate calculations
Authors: Walshaw C. D. , Rodgers C. D.
Published: February 2007

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

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

Much micrometeorological work to date has assumed, or tried to ensure, that conditions of horizontal homogeneity exist at and near the earth's surface. The present paper reports an observational study of the variation in the meteorological elements with distance and height downwind of a pronounced discontinuity from dry to wet surface conditions. In particular the temperature and humidity fields were observed together with the changes in the radiative‐balance components and in the wind structure. It was found that temperature and humidity changes at a height of 5 cm within 16 m of the discontinuity were commonly as much as 5$C and 5 g m−3 respectively. Theoretical treatments of the problem are outlined, and a slight modification of Philip's (1959) analysis is used to compare observed and predicted changes in temperature and humidity with distance downwind up to a height of 150 cm. It is found that the observed humidity changes are in good agreement with expectations, but that the measured temperature changes are about half those predicted. Changes in the evaporation rate in various distance intervals downwind from the leading edge have been computed. These are compared with an estimate of the rate which would have occurred under the same conditions from a wet area of infinite extent.

The discrepancies between theory and observation are attributed to the fact that the available theory fails to take into account the (demonstrable) differences in the aerodynamic properties of the adjacent surfaces. There is scope for further theoretical and experimental work on this matter.
A note on horizontal dispersion from an instantaneous ground source
Authors: Gee J. H. , Davies D. R.
Published: February 2007

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

The direct cell of the winter hemisphere is shown to extend across the Equator to at least 5° latitude in the summer hemisphere. the meridional circulation across the Equator is evaluated for the months January, April, July and October.
The height variation of vertical heat flux near the ground
Authors: Elliott W. P.
Published: February 2007

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

Ice needles were grown from the vapour on extremely fine quartz fibres situated inside a diffusion chamber. When temperature gradients were applied to the needles charge was separated within them; the colder end became positively charged and the warmer negatively charged. the magnitude of the charge separation was determined by measuring the deflection of the needles in a weak electric field and was in approximate agreement with Mason's equations.

Measurement was made of the charge acquired by an ice needle when it was momentarily touched against a dendrite inside the diffusion chamber. When the needle was warmer than the dendrite it acquired negative charge, and when it was colder it acquired a positive charge. the magnitude of the charge transfer was explicable approximately in terms of Mason's equations.
Correlations in the vertical component of the wind at heights of 600, 1,600 and 2,600 ft at cardington
Authors: Angell J. K.
Published: February 2007

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

Transpiration from a low, closely matted perennial grass has been measured daily by a floating lysimeter, over a period which included a long natural drought. Transpiration was found to continue at a level determined by the physics of the environment until all the available moisture in the root range was exhausted. This supports Veihmeyer's hypothesis that available water is freely available to the plant between field capacity and wilting point.
A derivation of the meridional velocity profile
Authors: Smith R. C.
Published: February 2007

The meridional velocity profile in the lower troposphere is derived from the zonal velocity profile by the introduction of the concept of an eddy viscosity varying with latitude. the amplitude of the eddy viscosity is then deduced and compared with previous results.
Self‐charging of melting ice
Authors: Maccready P. B. , Proudfit A.
Published: February 2007

A brief laboratory investigation was initiated to try to duplicate a phenomenon which had been repeatedly observed in certain flight measurements during the Flagstaff cumulus studies: the apparent strong negative charging of ice hydrometeors in the final stage of melting during their fall outside of the cloud. Sample ice structures of 1 cm3 from distilled water were melted in an 8 m sec−1 air stream at ambient temperatures. Regardless of the technique of measurement used (current into the sample, charge into the sample, or charge into an open Faraday cage around the sample), certain features were observed consistently: (a) a positive charge was acquired by the sample, (b) the magnitude of the charge was of the order of 30 picocoulombs (0.1 esu), and (c) the acquisition of charge occurred primarily during the later portion of the melting process. Generally similar but more erratic results were obtained with actual hail samples.

The sign of the charging was opposite to that observed in the flight measurements, and the magnitude of the charging was far less, but the correlation of the charging with the final stage of melting agreed with the results of the flight tests. Careful laboratory tests previously reported by Dinger and Gunn also showed positive charging during melting, and the charging correlated with the amount of dissolved gas and hence bubbles. It is felt that the charging effect is real and is probably primarily associated with effects from bubbles during melting, and that the disagreement in sign and magnitude between the laboratory and flight measurements may be attributable to the large differences in ambient conditions and differences in the physical and chemical properties of the hydrometeors.
Exchange between water droplets and tritiated water vapour
Authors: Booker D. V.
Published: February 2007

Measurements have been made of the activity collected by a stream of distilled‐water droplets falling through an atmosphere saturated with tritiated water vapour. The results, combined with those of Friedman et al. (1962), confirm theoretical predictions of the rate of exchange between droplets of radius 40‐1500 microns and the surrounding vapour.
Short‐range vertical diffusion in stable conditions
Authors: Thompson N.
Published: February 2007

Experiments have been carried out to determine vertical diffusion in stable conditions at distances of 100 or 200 m from a continuous cross‐wind line source. Simultaneous measurements of vertical turbulence provide the opportunity to test an empirical method of estimating diffusion from wind fluctuation measurements, based essentially on the ideas of Hay and Pasquill (1959), but also attempting to take into account the variation of turbulence with height. The results suggest a fairly systematic variation with stability of the ratio of the Lagrangian and Eulerian scales of turbulence, from values of about two in near neutral stability, to at least ten in rather stable conditions.
Diabatic influence on turbulent wind fluctuations
Authors: Klug W.
Published: February 2007

Mean values of dimensionless characteristic quantities of turbulence near the ground in relation to stability are given, as derived from data published by Lettau and Davidson (1957).
Atmospheric pressure waves from the Japanese earthquake on 16 June 1964
Authors: Bowman G. G. , Shrestha K. L.
Published: February 2007

Pressure waves have been recorded at Brisbane, 7,400 km from the epicentre of an earthquake in Japan. Calculated group velocities for the three prominent oscillations with periods of 168 sec, 70 sec and 60 sec are consistent with theoretical values. The maximum amplitude recorded was 58 μ bar.
Temperature structure in and above a tropical forest
Authors: Baynton H. W. , Hamilton H. L. , Sherr P. E. , Worth J. J. B.
Published: February 2007

A micrometeorological investigation in the tropical forest of north‐western Colombia has provided new data on forest temperature profiles and the factors controlling the profile shape. The lapse rate above the forest canopy is a direct function of the increase in temperature between the surface and the canopy. The level of maximum temperature is not at the top of the canopy. Thus, the Colombian forest temperature profiles are unlike other forest profiles previously reported in the literature.
Radiative cooling in the vicinity of inversions and the tropopause
Authors: Staley D. O.
Published: February 2007

The distribution of radiative cooling in the vicinity of a temperature inversion in the middle troposphere is calculated for several distributions of humidity. When mixing ratios are high throughout the inversion radiative cooling acts to erode the inversion (minimum cooling at the base, maximum cooling at the top). When mixing ratio decreases rapidly upward from the inversion base most of the inversion is a region of reduced cooling, while maximum cooling amounting to several degrees per day occurs in the vicinity of the inversion base. The region immediately below the inversion base is subject to strong radiative destabilization.

Verification of the theoretical cooling rates is sought in ten radiometer‐sonde ascents at Tucson, Arizona. The radiometer‐sonde is only marginally applicable to determining the radiative cooling distribution in the vicinity of the inversions, and random radiometer‐sonde errors and consequences of slant ascent are examined in detail.

The radiometer‐sonde measurements, when averaged, verify that radiative cooling is so distributed as to tend to maintain the inversion, showing maximum cooling of the order of 2°C day−1 at and below the base and minimum cooling of the order of 1°C day−1 in the upper part of the inversion. No verification was found for the theoretical destabilization of the layer below the inversion base, although errors and scatter of measurements obscure the true distribution.

All ten radiometer‐sonde ascents also penetrated the tropopause, and warming or minimum cooling was found at or very near the tropopause in every ascent. Hence the tropopause must be maintained by processes other than radiation.
The role of wind shear in horizontal diffusion of ambient particles
Authors: Smith F. B.
Published: February 2007

A change in the wind vector with height can have a very marked effect on the diffusion of tracers. Corrsin (1953), Saffman (1962) and Högström (1964) have shown that at large distances from the source of a tracer the horizontal spread of the cloud varies with time t like t3/2, provided the velocity shear is maintained over a sufficient depth of the atmosphere. Their result is extended in two ways, firstly to all values of t, and secondly by taking into account the correlation between horizontal and vertical eddy velocities. The most significant result of the latter effect is to reduce the displacement of the plume at any level in the direction of the shear. At small times of travel, it is shown that the relative spread is actually less in the presence of shear than predicted by the conventional ‘Taylor’ method.
Radiometric measurements of emission from stratospheric water vapour
Authors: Williamson E. J. , Houghton J. T.
Published: February 2007

Measurements of the total downward emission from the earth's atmosphere in the region 5.5 to 8 μ have been made to heights around 30 km using a balloon‐borne radiometer. The instrument employs a liquid‐air cooled detector of gold‐doped germanium, the responsivity of which increases with height, enabling measurements to be made over about four orders of magnitude. An all‐up weight of 2.5 kg allows the apparatus to be carried on a conventional radiosonde balloon.

A method has been devised for interpreting ascent data in terms of the distribution of atmospheric water vapour. The analysis of an ascent made in September 1963 is described in detail. Results are presented which indicate stratospheric mixing‐ratios in the region of 3 × 10−6 g g−1 at least up to 25 km. A large downward flux of radiation observed at the highest altitude was interpreted as emission from sources other than water vapour.
The effect of electric charges upon collisions between equal‐size water drops in air
Authors: Woods J. D.
Published: February 2007

Streak photographs of collisions between equal‐size drops carrying electric charges of opposite sign show a marked attraction immediately before coalescence occurs. For drops of radius R < 40 μ, the coalescence rate increases linearly with drop charge once a threshold value of about 5 × 10−5 e.s.u. has been reached; below this threshold there is no effect. For drops of R ≧ 40 μ, which coalesce spontaneously by wake attraction, even when uncharged, the coalescence rate increases linearly with drop charge. Charges of the same sign inhibit coalescence entirely for drops of R < 40 μ, and reduce the coalescence rate by a factor of five for drops of radius R = 40 μ.
Thermally driven diurnal tide in the atmosphere
Authors: Lindzen R. S.
Published: February 2007

The theory for the diurnal tide in the atmosphere is reviewed and the appropriate Hough Functions (including those with negative equivalent depths) are described. The main thermal drives for the diurnal tide — insolation absorption by O3 and H2O — are described. The theory is then used to compute the atmosphere's response to the thermal drives. It is shown that the small amplitude of the diurnal surface pressure oscillation results from most of the thermal drive being used to activate trapped modes. The calculated winds are in reasonable agreement with observations of the diurnal wind oscillation from the troposphere to the upper mesosphere. In addition the tidal wind agrees strikingly with single time observations of the total wind in the upper‐air. The temperature and vertical wind distributions and the upward flux of energy due to the diurnal tide are also calculated. The last item amounts to 6·8 ergs cm−2 sec−1 at the Equator which is about 2·5 times the downward solar flux in bands absorbable in the thermosphere. The average tidal flux over all latitudes is, however, considerably smaller.
Flux‐gradient relations near the ground in unstable conditions
Authors: Charnock H.
Published: February 2007

Swinbank's observations at Kerang (February 1962) are used to estimate the variation with the stability parameter ζ(≡ z/L) of the Monin‐Obukhov universal function φM (≡ u,∗︁−1 kz δu/δz).

A plot of Ri against ζ is used to derive the approximate variation of α (≡ φM/φH = KH/KM) with ζ.
An experimental study in micro‐meteorology
Authors: Swinbank W. C. , Dyer A. J.
Published: February 2007

A description is presented of the experimental techniques used on four micrometeorological expeditions. The instrumentation was designed to provide half‐hourly mean values of wind speed, temperature and humidity at a number of levels up to 16 metres, and of the vertical fluxes of heat, water vapour, net radiation and sensible heat into the ground. The observational material is to be published separately.

Analysis of the observations, all for the unstable case, shows close similarity between the turbulent transfer processes for heat and water vapour over the whole range of stability represented by the measurements. Both are more strongly influenced by instability than the exchange of momentum, the difference in behaviour becoming more marked with increasing instability. It is suggested that the similarity between heat and water vapour transfer is due to a correlation between the temperature and specific humidity of the air which originates at the evaporating surface.
A criticism of Bernstein's new dimensional approach to the flux‐gradient relationships near the ground
Authors: Calder K. L.
Published: February 2007

This paper discusses Bernstein's application of a generalized method of dimensional analysis, proposed by Huntley, to the Monin‐Obukhov problem of the flux‐gradient relationships in the thermally stratified air layer near the ground. It is concluded that the Huntley method is not a valid general procedure although, in disagreement with a conclusion of Bernstein, it is shown that the purely formal use of this technique leads to results that are actually valid under the very special conditions of free convection. This circumstance arises from the absence of any characteristic length scale under conditions of free convection in the surface layer.
The photochemistry of stratospheric ozone
Authors: Dütsch H. U.
Published: February 2007

A short review of the photochemical theory in a ‘dry’ atmosphere is given. It is shown that the difference between theory and observations concerning the vertical gradient of n3 (molecules of ozone/cm3) in the upper stratosphere, where photochemical equilibrium may be assumed, can hardly be accounted for by observational uncertainties. It seems, however, not impossible to reconcile theory and observations by parametric adjustment.

A semi‐quantitative theory of ozone in a ‘wet’ stratosphere is developed and the relative importance of different types of reactions is discussed. No reliable quantitative conclusion can be drawn at present due to large uncertainties in a number of parameters. In comparing vertical ozone distribution from this theory with observational data and considering the resulting change in relaxation times compared to the ‘classical’ theory, it is concluded that the influence of reactions of O and O3 with active hydrogen compounds cannot be as strong as that derived from the use of Hunt's reaction rates.
Concerning the existence of Taylor columns in atmospheres
Authors: Stone P. H. , Baker D. J.
Published: February 2007

The limitations on the conditions necessary for Taylor columns to exist in a compressible atmosphere are discussed. It is pointed out that the effect of baroclinicity precludes the existence of Taylor columns in the terrestrial atmosphere. The conditions in Jupiter's atmosphere are considered and it is shown that because of the effects of stratification and of baroclinicity Taylor columns can exist in Jupiter's atmosphere only under rather special conditions.
Day‐time long‐wave radiation from the sky
Authors: Paltridge G. W.
Published: February 2007

Six months of records of the hemispheric flux F of long‐wave radiation at Aspendale, Victoria, are analysed. A day‐time correction to Swinbank's formula for the radiation from clear skies is established, and this correction is probably applicable also to other more accurate formulae which include a term dependent on screen level humidity. It varies with time of day and season, but is of the order of − 3 mW cm−2 on summer afternoons. The correction is applied to all‐weather data, and at Aspendale the average long‐wave radiation at the ground due to clouds is found to be 0.6 mW cm−2/tenth of cloud cover. The mean value of F under cloudy skies is sensibly constant throughout the day, and is not greatly influenced by the diurnal variation of screen temperature.
Remote sounding of the atmospheric temperature profile in the presence of cloud
Authors: Rodgers C. D.
Published: February 2007

The present state of the art of retrieving the atmospheric temperature profile from remote measurements is briefly described, and methods based on maximum probability and minimum variance criteria are discussed. A maximum probability method is derived for the case of a cloudy atmosphere and synthetic examples of its use are given. The method is numerically fast and is capable of being generalized to incorporate other kinds of information. Such extra information might be for example surface temperature, cloud estimates from television pictures or forecast profiles.
Flux‐gradient relationships in the constant flux layer
Authors: Dyer A. J. , Hicks B. B.
Published: February 2007

An analysis is made of the Monin‐Obukhov function ΦM in the familiar wind profile equation, using data from two recent expeditions to Gurley (New South Wales) and Hay (New South Wales). In one, the friction velocity u* is determined directly by the eddy correlation method, and in the other, conducted during mid‐winter when small heat‐fluxes were experienced, by the use of a friction coefficient applied to a low‐level wind.

By collating with a similar earlier analysis for heat and water vapour transfer, the variations of ΦM, ΦH and ΦW with stability are presented in tabular form in the z/L range − 0.01 to − 1.0. Within this range the empirical relationships ΦM = (1 − 16 z/L)−1/4 and ΦH, W = (1 − 16 z/L)−1/2, and the implied equality between Ri and z/L, are found to approximate the data to within a few per cent.
An experimental study of Reynolds stress and heat flux in the atmospheric surface layer
Authors: Haugen D. A. , Kaimal J. C. , Bradley E. F.
Published: February 2007

The paper describes an experimental programme to study the characteristics of momentum and heat transport in the first 22‐6 m of the atmosphere. Sonic anemometers and fine platinum wire thermometers were used for flux computations by the eddy correlation technique. Two drag plates were used to measure the surface stress.

The results indicate that the fluxes are constant with height to within ± 20 per cent provided a long enough averaging period is chosen. Shorter averaging periods (15 min or less) show considerable variation in the fluxes and in their vertical gradients especially during unstable conditions. It appears that much of this variability can be attributed to the strong effect on the fluxes of submesoscale circulations. The momentum flux gradient seems to be particularly sensitive to these circulations.

The most consistent estimates of u* were obtained from the drag plates. They show much less scatter when used in similarity relationships than estimates obtained from the eddy correlation technique at higher levels. However, because of inherent difficulties in installing the drag plates in such a rough surface, their absolute reading was obtained by calibration against the eddy correlation measurement.

The correlation γUW, between the longitudinal and vertical components of the wind, is generally much smaller than γWT, the correlation between the vertical component and temperature. With increasing instability γWT increases to a value of about 0‐6 while γUW drops to negligible levels.
Spectral analysis of an aircraft observation of gravity waves
Authors: Axford D. N.
Published: February 2007

The characteristics of a full spectral analysis of an aircraft observation of gravity waves in the lower stratosphere are demonstrated. It is shown that the cross‐spectral quantities associated with the waves have characteristic properties which can be looked for in the analysis of more complex situations.