bluuebunny/crossref_metadata_2025 huggingface dataset:
Air pollution aspects of the London fog of December 1952
Authors: Wilkins E. T.
Published: February 2007

This four‐day fog caused at least 4,000 deaths and much illness; it therefore ranks as the most disastrous event of its kind known to have occurred anywhere in the world. For the first time in an incident of this kind extensive measurements were made of the daily concentrations of smoke and sulphur dioxide and of the general pattern of pollution throughout the area.

Mean concentrations of smoke and sulphur dioxide at 12 daily test‐sites increased sharply on the first day of the incident and, after 3 to 4 days, averaged 1.6 mg/m3 and 0.7 parts per million respectively, or about 5 to 6 times normal. At individual sites in the central London area concentrations rose to 10 times normal.

There was a striking parallelism between the mean daily concentration of smoke and sulphur dioxide and the total number of deaths on those days but the latter returned the more slowly to normal.

A few data, relating to a severe London fog of 1948, indicated that the concentrations of pollution then reached about 50 to 70 per cent of the 1952 values.

The approximate distribution of sulphur dioxide is shown on a map which indicates zones of maximum pollution mainly in the riverside areas, and particularly Westminster and adjacent boroughs.
Five flights through a thunderstorm belt
Authors: Jones R. F.
Published: February 2007

Analysis of accelerometer and other aircraft‐instrument records taken on five flights through thunderstorms shows that it is possible to obtain the detailed structure of the vertical air currents within the clouds. A feature of the clouds studied was the close proximity of upward and downward air currents of comparable magnitude, exceeding 20 ft/sec on occasions. Frequency and intensity of gusts increased markedly on entry into cloud and correlation with the radar echo received from the storms showed that all the biggest gusts were recorded within the echoing volume. On four out of five occasions when lightning was seen the aircraft was not in any appreciable upward or downward current, and on all five occasions the cloud had already attained its maximum development.
A note on computed transports of angular momentum in a theoretical model of the general circulation
Authors: Rogers M. H.
Published: February 2007

Angular momentum transports due to mean meridional circulations and horizontal exchange processes are computed for a theoretical model. It is found that, in high latitudes, the transport due to mean meridional circulations is less than 1 per cent of that due to horizontal exchange processes. In the tropics, however, the transport due to mean meridional circulations is seen to dominate that due to horizontal exchange processes. It is suggested that a variable coefficient of eddy viscosity would have to be used in order to explain observed motions on a synoptic scale.
Some aspects of the variability of annual rainfall over the British Isles for the standard period 1901–30
Authors: Gregory S.
Published: February 2007

Although the map of mean annual rainfall in the Climatological Atlas of the British Isles is for the period 1901–30, those maps which illustrate aspects of the variability of annual rainfall have not been presented for the same period. In this paper, the relative variability for the standard period 1901–30 is mapped and examined, and compared with the 1881–1915 pattern. This is followed by a brief commentary on the distribution of years of highest and lowest rainfall, the percentage relationship between these extreme values and the average, and the extreme variability of the annual rainfall, all these also being for the period 1901–30.
Some recent measurements of humidity from aircraft up to heights of about 50,000 ft over southern England
Authors: Murgatroyd R. J. , Goldsmith P. , Hollings W. E. H.
Published: February 2007

The humidity of the air was measured with a pressurized Dobson‐Brewer hygrometer in a Canberra aircraft up to heights of about 50,000 ft over southern England on 35 occasions during 1954. The frost point decreased with increasing height in the stratosphere and usually approached a constant value of − 115°F to − 120°F a few thousand feet above the tropopause.
Preliminary studies of the distribution of particles at medium range from a ground‐level point source
Authors: Pasquill F.
Published: February 2007

As a basis for planning a comprehensive study of the diffusion of airborne material over distances up to 100 mi a small number of exploratory experiments was carried out during February‐April 1955, using as a tracer a fluorescent pigment similar to that described by Braham et al. in Trans. Amer. Geophys. Un., December 1952. Samples were taken at distances up to 40 mi downwind of a ground‐level source and at heights up to 4,000 ft, using an impactor with a receiving surface in the form of a drum, the instrument being carried across the cloud in a Land‐Rover and a Hastings aircraft of the Meteorological Office Research Flight based at R.A.E., Farnborough.

The direction and speed of travel of the clouds were on the average closely in accordance with the measured vector mean wind over the first 2,000 or 3,000 ft, individual deviations therefrom being ± 5° in direction and ± 4 mi hr−1 in speed.

The conditions were mainly moderately unstable in the lower layers with overhead inversions at heights ranging from 2,000 to 7,500 ft. Effective extreme cloud widths ranged from about 40° (angle subtended at source) at 5 mi to about 20° at 40 mi. Vertical diffusion in the layer between the ground and the inversion appeared to be an order of magnitude more rapid than in the lower atmosphere in neutral conditions of stability. No decisive evidence was found as regards the effect of an overhead inversion in limiting the extent of vertical diffusion.

The difficulties encountered in obtaining and interpreting the distribution downwind of a source of short duration emphasize that it would be more profitable to use a longer duration source and to carry out the sampling operations away from the leading and trailing edges of the cloud.
Airflow over mountains: The lee‐wave amplitude
Authors: Corby G. A. , Wallington C. E.
Published: February 2007

Although orographic lee waves are probably common over the British Isles, their amplitude is so critically dependent on airstream characteristics and on the scale of local topography that they are likely to be insignificant unless a variety of conditions is satisfied. Precise criteria for large‐amplitude waves cannot be formulated for airstreams in general, but simplification of the general problem illustrates the pronounced effect of mountain size and shape, stability and wind speed on the lee‐wave amplitude.
The decay of the ice‐nucleating properties of silver iodide released from a mountain top
Authors: Smith E. J. , Heffernan K. J.
Published: February 2007

Silver‐iodide freezing nuclei, together with a tracer of zinc‐sulphide particles, were released from a mountain top and detected in an aircraft. The ice‐nucleating properties of the silver iodide decayed in the daytime but not at night. The ambient temperature did not appear to affect the daytime rate of decay. The top of the smoke plume rose no higher than in previous experiments when it was released from a flat plain.
Temperature differences in the South Tyne Valley, with special reference to the effects of air mass
Authors: Richardson W. E.
Published: February 2007

Observations at three stations have been analysed to determine the teperature profile of a N‐S valley. The relationships between them have been classified, their frequencies tabulated, and further analyses undertaken linking these relationships to air‐mass types. An attempt has been made to correct the observed values for the period under review (October 1952 to May 1954) to the twelve years' basis used by Belasco for his work on air‐mass frequency. It is concluded that air‐mass properties have an effect upon the relationships other than those resulting from differences of wind speed and direction, radiation, and insolation.
Seiches in lough neagh
Authors: Darbyshire J. , Darbyshire Mollie
Published: February 2007

Records of seiches in Lough Neagh during April 1949 were investigated. Fourier analysis of the records indicated three period bands centred round 1.6 hr, 1.15 hr, and 0.75 hr. The two longer periods appeared to have a nodal line across the centre of the lake, parallel to the shorter sides. Methods of deriving these periods in terms of the shape of the lake basin are discussed.

The amplitudes of the seiches were compared with the wind records and a high degree of correlation was obtained between the amplitude and Wdθ/dt, where W is the wind speed and dθ/dt is the rate of change of wind direction.

An estimate was made of the coefficient of damping of the seiche amplitude and it was found to correspond to a decay to half value in 10 hr.
Intracloud lightning discharges
Authors: Smith L. G.
Published: February 2007

Slow electric‐field changes produced by lightning discharges within clouds have been recorded simultaneously at two stations 13.2 km apart. It is found that the same cloud discharge may give field changes of different types (simple and complex), or of opposite sign (reversal effect), or both, at the two stations. Two main types of complex slow field change are described. The interpretation of slow field changes is discussed in terms of movement of charge. It is shown that, in the most frequent case, the cloud discharge involves the raising of negative charge.
The intensity of turbulence in convective clouds
Authors: East T. W. R.
Published: February 2007

Calculations of collision rates between cloud droplets in turbulent air show that this would be an effective precipitation mechanism in cumulus if the r.m.s. turbulent acceleration were about 3 times that due to gravity. An estimated value, based on published records of flights through thunderstorms, is about one‐sixth of gravity. In the absence of more direct evidence, it seems that turbulence is not an important factor in convective precipitation.
A dynamical model for large‐scale tropospheric and stratospheric motions
Authors: Gates W. Lawrence
Published: February 2007

A physical model of the atmosphere is postulated in which both the troposphere and stratosphere are characterized by a uniform thermal wind and a constant static stability, and are separated by a tropopause across which these quantities are discontinuous. Assuming the tropopause to be quasi‐isobaric, a simplified model for the mean velocity, temperature and vertical motion fields of both the troposphere and stratosphere, the velocity near the earth's surface, and both the horizontal and vertical motion at the tropopause is constructed. The model may be regarded alternatively as a four‐parameter or four‐level model, but it is felt to avoid the primary disadvantages of the exclusive use of either the parameterized or layered formulation. Analysis of the special case of an equivalent‐barotropic stratosphere indicates the existence of systematic tropopause variations, with the vertical motion at this level generally in phase with that of the mid‐troposphere, and with a system of opposing vertical motion higher in the stratosphere. These features are in general agreement with the results of observational and synoptic research, although the details of the role of the tropopause must await further calculations. The analysis of the stability of tropospheric perturbations in a baroclinic zonal current shows a stabilizing influence of the stratosphere on the initial amplification of the disturbances. The minimum vertical shears required for instability with a basic jet current of 40 m sec−1 are more than twice those required without a stratosphere, and are shown to lie between the mean summer and winter shears in the zone of maximum westerlies.
Air motion over a heated land mass: II
Authors: Smith R. C.
Published: February 2007

In a previous paper (Smith 1955), the problem of the resultant theoretical velocity field that arises from the diurnal variation of heating of a land mass with an initially stationary air mass was considered. The present paper considers the same problem with an initial overall velocity. Henceforth the first paper (Smith 1955) will be referred to as Part I.

The same heat function is used as in Part I for the time and horizontal variations, but the vertical variation is amended for closer approximation to the different circumstances. The difficulty of the boundary condition at infinite height is overcome by associating the solutions with those of Pt. I.

The resulting surface temperatures and vertical velocities at different times are shown in tables and graphs.
The thermodynamics of saturated air: A contribution to the classical theory
Authors: Saunders P. M.
Published: February 2007

The temperature attained in the reversible and pseudo‐adiabatic expansion of air saturated with respect to liquid water is taken as a reference; the temperatures attained in the following expansions from the same initial state are then compared with it: (a) the ice‐saturation pseudo‐adiabatic process (b) the water‐saturation adiabatic process (c) the ice‐saturation adiabatic process.

The results of these comparisons are summarized in Figs. 1 to 5 of this paper.

Similarly, the cloud virtual temperature, the virtual temperature adjusted for the weight of suspended particles, attained in water‐saturation adiabatic expansion, is compared with that attained in water‐saturation pseudo‐adiabatic expansion; Fig. 6.

The implications of these calculations for the properties and behaviour of cumulus are commented upon.
Ozone information from sky observations
Authors: Walton G. F.
Published: February 2007

The information of the vertical distribution of atmospheric ozone obtainable from measurements of scattered sunlight received from various directions in the sky is considered. It is shown that observations in a particular direction in the sky could replace, but would not supplement the customary zenith sky observations, except in high latitudes at certain seasons of the year. Observations in various directions in the sky would be equivalent to zenith sky observations made throughout the day.
Some observations of bent plumes
Authors: Ball F. K.
Published: February 2007

Some measurements of the height of the smoke downwind from a 40 kw heat source under conditions of light wind are presented. The results are compared with Priestley's and Sutton's theories. A general non‐dimensional solution of Sutton's equation is developed which can be applied to bent plumes on any scale.
The meteorology of North Greenland during the midsummer period
Authors: Hamilton R. A.
Published: February 2007

An elevated ice sheet of the size of Greenland has a strong influence on its own weather. On account of the cooling by radiation of the snow surface and of the lower layers of the air there is a tendency for a system of low‐level outflowing katabatic winds to be set up. The weather is also influenced by the cyclonic systems characteristic of middle latitudes and their associated fronts.

Northern Greenland is far from the main track of Atlantic depressions, and as the inland ice is here at its widest, conditions appear suitable for the establishment of the glacial anticyclone which would be expected to be disturbed only rarely by cyclonic systems. In order to study the frequency of these disturbances, and the normal meteorological conditions in the undisturbed periods, an investigation has been made of the weather in the area during the six midsummer weeks of 1953, in particular of the observations made at “Northice”

“Northice” i not an accepted place name but in used in this paper for convenience.

near the crest of the ridge of the inland ice and at Britannia Sø near the east coast.

Owing to the elevation of the ice sheet mean sea‐level synoptic charts cannot be used satisfactorily, and a method of drawing 700 mb charts and using the same techniques as are used in temperate regions for analysis of mean sea‐level charts has been developed. As the weather is predominantly fine all occurrences of appreciable cloudiness, precipitation and abnormal surface wind are significant and in almost all cases were due to cyclonic disturbances and their associated fronts which could be followed on the series of 700 mb charts. A total of 16 depressions or waves caused 19 disturbances (in three cases the effects of the warm and cold fronts were clearly separated) at either one or both of the two stations, but only 5 of these caused precipitation exceeding 1·0 mm at either station.

During the anticyclonic period of 11 days when the 700 mb wind was light and variable the weather at Northice was fine with a katabatic surface wind of 280° 13 kt. The diurnal range of temperature at Northice was 6·8°C but only 3·7°C at Britannia Sø. The diurnal variation of relative humidity was small. The upper winds at Northice were mainly S to W at low levels and S to E at 16 km.

A comparison of June 1953 with June 1954, and with statistics for other Greenland stations in other years, indicates that the midsummer of 1953 can probably be regarded as representative of a normal midsummer.
Temperature, humidity and cloud near fronts in the middle and upper troposphere
Authors: Sawyer J. S.
Published: February 2007

Exploratory flights through fronts beneath the jet stream confirm that a narrow frontal zone some 30 to 50 mi wide with sharp boundaries is often present at the 500 mb level. On other occasions the temperature changes are more diffuse. The air in and near the frontal zone is usually very dry and must have undergone subsidence.

Dynamic considerations suggest that the very strong temperature gradient of the frontal zone at 500 mb arises from the differential subsidence of air on the cold side of the jet stream which leads to a tilting of the isentropic surfaces.
The washout of lycopodium spores by rain
Authors: May F. G.
Published: February 2007

This report describes the determination of the washout coefficient of lycopodium spores by rain. The experimental results are in good agreement with those obtained theoretically by Chamberlain (1953) after allowance has been made for the varying raindrop spectra of different types of rain.
A synoptic study of day‐to‐day changes of ozone over the British Isles
Authors: Martin D. W. , Brewer A. W.
Published: February 2007

Two months of European ozone data are analysed in relation to 24‐hr trajectories determined from 100 mb contour charts. Significant correlations are obtained between vertical movements at 100 mb and non‐advective and local changes of ozone, 100 mb temperature and 100 mb vorticity. These confirm the importance of horizontal convergence as a dynamic effect in the lower stratosphere.

Further correlations are presented between these changes and the accompanying N‐S displacements in an attempt to relate short‐period phenomena and the observed global distribution of ozone. The results do not conform to the simple models of the atmosphere considered here.
Point‐discharge currents from natural and artificial points
Authors: Maund J. E. , Chalmers J. Alan
Published: February 2007

When point discharge occurs at an earth‐connected point, ions of one sign travel to earth through the point while ions of opposite sign travel away in the wind. This stream of ions reduces the potential gradient at the ground to leeward of the point below that to windward. Theory shows that, under suitable conditions, this difference in potential gradient is close to that predicted for a line of charge, even though the line is spread into a cone by turbulent diffusion. Measurements with point discharge from a 34 m mast show good agreement with theory, and this makes it possible to use the difference of potential gradient to determine the point‐discharge current through a tree. When applied to a line of trees, seasonal differences are found suggesting smaller currents from trees in leaf than from bare trees. Measurements with a 12 m sycamore tree in full leaf show no point‐discharge current even in potential gradients up to 7,000 v/m.
The diurnal temperature variation during the polar night
Authors: Hisdal V.
Published: February 2007

It is well known that if special types of days are considered separately, systematic diurnal temperature variations may be found to exist at polar stations even during the dark season. In the present paper it is shown that, in all probability, this phenomenon is of trivial nature and that a perfectly simple explanation of its origin is possible.
Interhemispherical features of the general circulation of the atmosphere
Authors: Rao Y. P.
Published: February 2007

Mean meridional wind components in the troposphere are computed at five stations along the Equator. Their significance is discussed in regard to mass exchange between the hemispheres. The eddy transport of heat across the Equator is found to be negligible. The possibility of seasonal exchange of heat between the hemispheres through meridional circulation across the Equator is discussed.
The statistical variation of wind with distance
Authors: Durst C. S.
Published: February 2007

Correlation coefficients have been formed between the winds at pairs of points, the correlation being made between components along the line joining the points and also between components at right‐angles. The original purpose was the derivation of the effective winds experienced by aircraft. However, certain results are found which appear to throw light on the application of turbulence theory to the large‐scale pattern of winds and hence it is thought that the results may be of more general interest.
A note on the synoptic climatology of Labrador‐Ungava
Authors: Barry R. G.
Published: February 2007

Aspects of the synoptic climatology of the Labrador‐Ungava peninsula are investigated with reference to a classification of airflow pattern types, formulated on the basis of synoptic weather maps for November 1956 to February 1958. The winters 1956–57 and 1957–58 exhibit, respectively, marked negative and positive temperature departures and the temperature and precipitation characteristics of the airflow types are discussed for these two seasons. The validity of the airflow categories is statistically tested.
Wind, temperature and humidity distribution at some cold fronts over SE. England
Authors: Miles M. K.
Published: February 2007

Recent evidence from frequent radar‐sonde soundings at Crawley (Sussex) has been studied along with earlier published evidence to establish that a marked fall in humidity occurs directly above the front in a more or less random sample of cold fronts crossing southern England. This usually happens at levels above 700 mb and without a corresponding fall of temperature or any considerable change in wind direction at these levels.

Evidence from trajectories shows that the dry warm air is drawn from a cold source and warmed dynamically before it enters the frontal zone. At this stage it is usually moving faster than, and in the same direction, as the warm moist air and this contributes to the formation of a marked humidity gradient at the junction of the two air masses.

The air may sometimes be ascending at this junction, but there is no clear evidence that a wedge of cold air (where it exists) has anything to do with the vertical motion.
The structure of the arctic winter stratosphere over a 10‐yr period
Authors: Wilson Cynthia V. , Godson W. L.
Published: February 2007

A series of 100‐mb temperature maps was drawn up for the winters 1949‐1950 to 1958‐1959 using 10‐day mean data. These maps were used to summarize the large‐scale events of each winter and of the ten winters in general. The results suggest the existence of two major patterns, both highly persistent.

(i) An asymmetric pattern with a warm ridge over east Siberia‐Alaska and an elliptical cold‐core vortex over Eurasia.

(ii) An eccentric bi‐polar distribution, the trough line extending from central Canada to central Siberia.

The Aleutian ridge and Eurasian trough are quasi‐stationary features, common to both regimes, while the Canadian and North Atlantic sectors experience the greatest change from one regime to the other ‐ alternating warm ridge and cold trough. Both the regional climatology of the arctic winter stratosphere and the variations in the sequence of events from year to year for the Arctic as a whole, are described in terms of these two features and two alternating patterns.

The striking asymmetry of both patterns in the stable stratosphere appears to require an external forcing agent, and this analysis tends to highlight the role of tropospheric activity.
Absorption in the stratosphere by some water‐vapour lines in the v2 band
Authors: Houghton J. T.
Published: February 2007

A study has been made of some lines in the solar spectrum, as observed from an aircraft, due to absorption by atmospheric H2O16 and H2O18. The integrated absorptances for these lines, calculated using theoretical line strengths and various water‐vapour distributions, are compared with observed values. The water‐vapour distribution which gives the best fit is one which is very dry (mixing ratio 1·5 × 10−6) in the lower stratosphere, but considerably wetter (up to 5 × 10−5) above 25 mb.
The space‐filtering of monthly surface temperature anomaly data in terms of pattern, using empirical orthogonal functions
Authors: Grimmer M.
Published: February 2007

In statistical long‐range forecasting the large volume of data makes some form of filtering imperative both to reduce the data‐handling problem and to exclude random elements which do not contribute to understanding or prediction. In this study, which is an exercise in the statistical technique of factor analysis, fields of 30‐day surface temperature anomaly for the years 1881–1960 are filtered in terms of sets of patterns specific to each calendar month. These are derived empirically, and so truly reflect the characteristics of the original fields. In the resulting representation, the volume of data may be reduced to one quarter while retaining 80 per cent of the original variance, and a study of seasonal variation shows that continentality and zonal thermal advection are at all times of year the most important factors in shaping the 30‐day anomaly fields.
Polynomial approximations to radiative functions
Authors: Rodgers C. D. , Walshaw C. D.
Published: February 2007

The following polynomial approximations to functions often needed in radiative transfer calculations were derived by standard Chebyschev methods after an initial transformation of the independent variable. They form a convenient method of computing these functions on an electronic computer, and were used by Dave, Sheppard and Walshaw (1963), with the exception of No. 1, which has been modified to cover the whole range of the variable.
An analysis of the fluctuations in the tropical stratospheric wind
Authors: Probert‐Jones J. R.
Published: February 2007

Numerical analysis of the zonal component of the wind at levels in the lower stratosphere at three tropical stations has enabled the period, amplitude and phase of the so‐called biennial oscillation to be found. There are two preferred periods, 27 and 22 1/2 months; the amplitude increases upwards from zero at the tropopause and is still increasing at the 30‐mb level; while the phase propagates downwards at a rate of about 1/3 radian/km.

An harmonic, whose period is exactly half the fundamental, is found whose phase propagates downwards at the same rate. From estimates of the time of arrival in the lower stratosphere of the 22 1/2‐month oscillation in the fundamental and harmonic, the level of origin can be put between 32 and 80 km. By assuming coincidence of the nodes before the westerly maximum of the fundamental and the harmonic at the level of origin, the three possible heights within these limits are found to be 43, 61 or 79 1/2 km.

The oscillation and its harmonic can account for over 90 per cent of the total variance in the monthly mean equatorial zonal wind.
Heating rates due to ozone computed by the curtis‐godson approximation
Authors: Clark John , Hitschfeld Walter
Published: February 2007

The heating produced by atmospheric ozone is calculated with the use of the Curtis‐Godson approximation, and the results are compared with rigorous computations performed on the same data by Hitschfeld and Houghton (1961). Agreement is good near the top and bottom of the ozone layer, while at intermediate heights, where the heating rates are particularly important, the approximation is not so successful. This pattern is confirmed by the use of the strong‐ and weak‐line criteria of Plass (1960). Although the applicability of the Curtis‐Godson approximation is thus found to be limited, there can be no question as to its convenience, and a simple radiation diagram for ozone, which makes use of this approximation, is prepared.
Waves in stratified media ‐ pt. iii
Authors: Sen‐Gupta B. K.
Published: February 2007

A previous paper (Sen‐Gupta 1962, Pt. II) dealt with exact solutions of lee‐wave terms in the most general case for large displacement waves in stratified media. the present paper deals with a case less general, but involving simpler solutions, which may have wide application if one of the constants of the general case is made zero. Formal solutions are also given for generalized solutions to equations exploited in the previous paper, and these may have application if flow near the disturbing influence is to be studied.
Dynamical aspects of the bi‐polar stratospheric circulation
Authors: Sawyer J. S.
Published: February 2007

The wind and temperature distributions in a ridge over Alaska and a trough over eastern America are examined during periods of steady circulation in the stratosphere with dominant wave‐number two. Comparison of vorticity near the ridge and trough suggests that flow at about 30 mb is approximately non‐divergent. the distribution of convergence and divergence at other levels is not simple, but as air passes from ridge to trough subsidence is probably dominant poleward of the wind maximum and ascent on the equatorward side. Changes in wind shear and wind speed are as important as changes in curvature in determining the vorticity changes.
The objective analysis of horizontal wind divergence fields
Authors: Eddy A.
Published: February 2007

Statistical evidence is adduced to support the contention that significant patterns are discernible in fields of divergence values computed from the horizontal winds using the Bellamy triangle technique.

An objective method is presented for determining:

the percentage of the variance of a given data field which is explainable using a statistical objective analysis technique on a specified observational network,

the principal wavelengths present in the data field,

statistically determined weight curves for the objective analysis of the field.

Space autocorrelation shows a 1,700 nautical mile wavelength to be dominant in the tropospheric divergence fields and the noise level to be about 10−5 sec−1. the case history of a developing storm is presented and the divergence patterns associated with various aspects of the development are shown to be in agreement with synoptic experience.
A mean motion model of the general circulation
Authors: Williams G. P. , Davies D. R.
Published: February 2007

Equations are constructed to represent quasi‐stationary mean flow of momentum and heat on a spherical earth, averaged over a long period of time such as a year and over latitude circles. The crucial shearing Reynolds stress associated with meridional transfer of zonal velocity is assumed to depend linearly on a product of the earth's angular velocity, Ω, and the meridional gradient of mean temperature; the shearing stresses associated with vertical transfer of zonal velocity and of meridional velocity are assumed to depend linearly on the vertical gradients of zonal and of meridional mean velocities respectively, and the mean eddy transfer of heat along a meridian is assumed to depend linearly on the mean meridional temperature gradient. All proportionality coefficients are taken to be independent of latitude. Two forms are assumed for the non‐adiabatic atmospheric heat source function, Q, used in the thermodynamic equation. In the first case Q is assumed known (from analyses of observations) as a function of height and latitude. In the second case, Q incorporates a heating term which is partly controlled by the model itself and represents some of the characteristics of sensible and latent heat transfer. A solution of the basic equations is obtained in both cases in the form of double expansions in powers of two parameters, one depending on Ω and the other on ΔT, the mean annual temperature difference between equator and pole. The solution is evaluated using Fourier techniques.

The series expansions are found to be reasonably convergent for realistic values of the various parameters involved, three terms only being required in the ΔT expansion and five terms at most in the Ω expansion, but extensive numerical evaluation by digital computer is involved: the region considered is bounded by the tropopause and lies between the equator and 70° latitude. The computed zonal velocity has the characteristic east‐west variation with latitude and a broad band maximum of 19 m sec−1 and the meridional velocity the characteristic tricellular structure. A poleward eddy angular momentum flux and polar inversion are predicted.

The results, through verification of the postulates, add support to the Rossby view of the general circulation in which the cyclonic‐scale eddies act to release potential energy of the atmosphere to supply their own kinetic energy and form the mean zonal kinetic energy. They further indicate the value of the reconstructed ‘austausch’ approach for this problem.
On the equation of atmospheric diffusion
Authors: Calder K. L.
Published: February 2007

Some simple transformation properties of the diffusion equation that has been classically used to describe turbulent transport in the atmosphere are briefly examined. The essential tensorial nature of the eddy diffusivity is emphasized and it is concluded that the standard form frequently adopted for the diffusion equation in the meteorological literature cannot be generally valid.
Local interactions between the sea and the air at monthly and annual time scales
Authors: Kraus E. B. , Morrison R. E.
Published: February 2007

A statistical analysis of wind, air, dew‐point and sea‐temperature records from all nine weather ships in the North Atlantic shows local variations between years which are highly significant when compared with variations within months. The fluctuations show a consistent pattern with a scale of more than 500 miles in the atmosphere and a persistence over several months. The horizontal extent of sea‐surface temperature anomalies appears to be somewhat smaller, but they tend to last longer than air‐temperature anomalies.

Short‐period variations in the flux of latent and sensible heat are due predominantly to atmospheric variations, particularly in winter. The effect of sea‐surface temperature anomalies is somewhat greater in summer, though it becomes significant only on the annual time scale.
The falling motions of loaded cylinders and discs simulating snow crystals
Authors: Jayaweera K. O. L. F. , Mason B. J.
Published: February 2007

The clustering, by wake capture, of thin cylinders and discs as they fall through a viscous liquid has been studied, and the relevance of the observations to the aggregation of snow crystals is discussed. The influence of captured cloud droplets on the orientation and falling motion of columnar and plate‐like snow crystals is inferred from the behaviour, in a viscous liquid, of solid cylinders and discs loaded with small spheres and from the motion in air of loaded discs of thin tissue paper. The orientation in the atmosphere of composite ice crystals in the form of columns with end plates may be inferred from the behaviour of cylinders capped by thin discs in a viscous liquid. These observations on the falling speed, orientation and aerodynamic stability of snow crystals are pertinent to their aggregation into snowflakes, their accretion of cloud droplets and dust particles, and to the optical effects they produce in the atmosphere.
The estimation of vertical diffusion over medium distances of travel
Authors: Thompson N.
Published: February 2007

Experiments have been carried out in which the vertical diffusion of a tracer has been measured after several kilometres travel. Simultaneous measurements of atmospheric turbulence provided an opportunity to use the treatment described by Thompson (1965) to estimate the ratio of the Lagrangian and Eulerian scales of turbulence. The scale ratio was again found to increase with an increase in stability, with a variation in magnitude from near unity in unstable conditions to around 15 in moderate stabilities.
Thermal conduction and viscosity and the choice of the upper‐level boundary condition in the theory of atmospheric oscillations
Authors: Giwa F. B. A.
Published: February 2007

Viscosity and thermal conduction are included in the current tidal oscillation theory. The solution in which the energy density remains finite as height increases is treated. For all equivalent depths for which the tide is oscillatory in the vertical direction, this solution is a wave whose energy propagates upwards, thus suggesting that the choice of ‘energy propagation upwards’ as the upper‐level boundary condition is consistent with the effect of damping at these levels. Similar work by Pekeris is discussed.
On Antarctic pressure variations
Authors: Loewe F.
Published: February 2007

The numerous stations which operated in Antarctica during the International Geophysical Year allow a more detailed study of the local distribution and of the displacements of pressure variations. From six‐hourly pressure data the times of occurrence of identifiable extremes have been determined. They are mostly later at the more westerly stations. For 15 months and seven stations, cross‐correlations of six‐hourly pressure values have been calculated for lags of multiples of six hours between 60 and — 60 hours. The correlations are in most cases highest for pressures at the eastern before the western station. The same result is found if six‐hourly and twenty‐four hourly pressure changes at different stations are correlated instead of the pressures themselves. No correlations of the same size occur if between Little America and Wilkes pressures and pressure changes at a station are correlated with later ones at a more easterly location. The existence and importance of Simpson's ‘antarctic pressure waves’ is thus confirmed.
Day and night measurements of ozone in the Southern Hemisphere
Authors: Kulkarni R. N.
Published: February 2007

Measurements of ozone using Dobson spectrophotometers at night on the moon in low and middle latitudes of the Southern Hemisphere and calculated by the ‘AD’ method did not show any significant difference between day and night. However, the ozone amounts calculated using individual wavelength pairs, without applying the haze correction, usually showed an increase in ozone at night, implying that the apparent increase in ozone was due to an increase in large particle scattering at night.

In middle latitudes, at Aspendale, Hay and Hobart, observations at night on the B (λλ 3088/3291) pair of wavelengths showed an apparent decrease of ozone at night. At Darwin, in low latitudes, there was no difference between day and night ozone when calculated on the B pair of wavelengths. This implies that greater radiation is received at the Earth's surface on about λ 3088, in middle latitudes. This enhanced radiation is tentatively attributed to the emission from the Herzberg band of molecular oxygen and to (terrestrial) OH emission at λ 3088, at night in middle latitudes. The latitudinal observations and their interpretations are consistent with existing knowledge regarding these emissions.

The absorption coefficients of ozone as calculated from Southern Hemisphere atmospheric measurements at these wavelengths and at these places differ from those obtained by Vigroux, but are consistent with those obtained by Dobson and Ramanathan in the Northern Hemisphere.
Models of cloud‐topped mixed layers under a strong inversion
Authors: Lilly D. K.
Published: February 2007

Theoretical models are constructed with the aim of relating, explaining and predicting features of a radiatively active turbulent cloud layer over the sea and under a strong subsidence inversion. Both dry aerosol clouds (no phase change) and wet clouds (with a phase change and latent heat exchanges) are considered. For the wet cloud case an important element of the theory is the requirement that the wet‐bulb potential temperature must increase upwards in the inversion. For both cases entrainment of the upper warm air is hypothesized to lie between upper and lower limits determined from the turbulent energy budget. The dry cloud case is solved for both steady state and transient results, with only the transient behaviour depending on the entrainment hypothesis. Only steady state solutions are presented for the more complex wet cloud case and these differ somewhat for the maximum and minimum entrainment limits. Observational data from Oakland, California are used for comparison with those steady state solutions, with results indicating the essential validity of the approach. Detailed comparisons, especially for determination of the most correct entrainment rate, are hampered both by inadequate measurement of the inversion properties and by uncertainties in the net radiation flux leaving the cloud top. Computations of the latter suggest that several presently used radiation models are still in serious disagreement, at least for application to downward flux under an inversion. It is suggested that the present theory provides a partial explanation of the origin of the trade wind inversion.
Radiative modification of selected vertical temperature distributions
Authors: Staley D. O. , Jurica G. M.
Published: February 2007

Radiative cooling rates at closely spaced vertical intervals were determined by the Brooks method applied to several types of soundings. Other cooling processes were neglected, and a new temperature distribution at a later time was determined by forward integration of the cooling rate. By repeating the procedure, temperature distributions were obtained at two‐hour intervals up to 24 hours.

The initial temperature distributions included: (a) a relatively moist inversion in the middle troposphere, (b) relatively dry inversions in lower and middle troposphere, within which moisture decreased rapidly upwards, (c) a relatively dry inversion in the upper troposphere, and (d) a smooth temperature distribution having a large moisture inversion. The distribution of cooling rates tended to wipe out the inversion with high moisture throughout (case (a)), and extremes of cooling decreased substantially over the 24‐hr period. In the vicinity of the relatively dry inversions in lower and middle troposphere (case (b)), cooling rates were relatively constant over the 24‐hr period, and so distributed as to maintain the inversion and substantially increase the hydrostatic stability in the lower part of the inversion. Radiative destabilization was noted after a few hours below the bases of the lower two dry inversions (case (b)) and just above the top of the moisture inversion in case (d).

The distributions of radiative cooling in the vicinity of a dry frontal zone are consistent with the orientation of isentropes with respect to the frontal zone in vertical cross‐section. Potential vorticity, because of its proportionality to hydrostatic stability, must undergo substantial changes in the vicinity of dry frontal zones.
Tropical cloudiness and rainfall related to pressure and tidal variations
Authors: Brier G. W. , Simpson Joanne
Published: February 2007

A definitive statistical relationship is established between tropical cloudiness and rainfall and the semidiurnal solar (S2) atmospheric tide, as manifested in the semi‐diurnal surface pressure variation. Pressure and weather data are used from Batavia (seventy years) and Wake Island (twelve years). TheS2tidal effect is shown to enhance cloudiness and rain near sunrise and sunset, and to suppress them shortly after midday and midnight. The analysis is based on (a) the fact that theS2amplitude varies by 15–20 per cent between months and by more than 100 per cent from day to day and (b) the amplitude of theS2wave as computed from the pressure data at a station is closely related to the 5–6 hourly pressure changes during the periods around 4–5 a.m. to 10 a.m., from 10 a.m. to 4 p.m., etc. The crux of the analysis is the demonstration that days with large 5–6 hourly pressure changes during these periods have large cloudiness changes (in the sense described above) during these same periods relative to days with small 5–6 hourly pressure changes.

Possible mechanistic connections betweenS2pressure tendencies and cloud properties are examined. The varying convergence‐divergence field is suggested as the main link. It is shown how the concentration of active cloud updraughts in the Tropics can permit cloudiness to be extremely sensitive to small divergence fields.

Finally, large‐scale simultaneous pressure changes over the Pacific Ocean area are shown and related to cloudiness changes. A need for re‐examination of the nature and origins of tropical disturbances is shown to exist, using the concept that possible small (terrestrial or extra‐terrestrial) triggers may set off significant changes in weather both locally and on the synoptic and global scales.
A note on the contributions of mean and eddy terms to the momentum and heat balances of the troposphere and lower stratosphere
Authors: Murgatroyd R. J.
Published: February 2007

The space‐time averaged zonal wind equation has been used in a two dimensional model to infer the mean meridional circulation of the Northern Hemisphere upper troposphere and lower stratosphere at the solstices. A three cell system is found with maximum meridional speed of 120 cm sec−1 in winter and 40 cm sec−1 in summer and vertical speeds of 0.3 cm sec−1 in winter and 0.1 cm sec−1 in summer. The lower stratosphere circulation shows a continuation of the tropospheric cells with speeds decreasing with height.

Using these results together with estimates of the eddy convergence terms and the ‘diabatic’ contributions based on values obtained from the literature the component terms in the zonal momentum and heat budgets are listed. In the former, in agreement with other workers, the main balance is between the convergence of the horizontal eddy flux and the mean meridional flow (Coriolis torque) terms. In the latter the balance is principally between the ‘diabatic’ term, the (subsidence) term due to the mean vertical flow and both the horizontal and vertical eddy heat flux convergence terms.

The limitations of the data on which the calculations are based are emphasized and estimations of the consequent uncertainties in the results are obtained by repeating the computations with different input data. In particular no measurements are available of the term due to the convergence of the vertical eddy flux of momentum. Most authors have assumed it to be zero but calculations have also been made here using values based on results given by Smagorinsky, Manabe and Holloway (1965) for their 9‐level general circulation model experiments.
Charge distribution in thunderstorm clouds
Authors: Ogawa T. , Brook M.
Published: February 2007

The negative charge involved in lightning flashes to ground is found to be distributed in a manner strongly dependent upon the direction of movement of the storm, and does not, in general, constitute a nearly vertical column as proposed by Malan and Schonland. Based on a study of electric field‐changes measured at two stations 10 km apart involving 539 return strokes from 84 flashes in 10 storms, we conclude that the horizontal component of the in‐cloud channel on the average exceeds the vertical component, and points in the direction of storm motion.

An analysis is given of the five methods of Malan and Schonland, on the basis of which we suggest that significant horizontal components are also compatible with their observations of a vertical column, and that the ‘nearly vertical’ aspect of the charge distribution has been over‐emphasized.