bluuebunny/crossref_metadata_2025_split huggingface dataset:
Calculations of Mie back‐scattering of microwaves from ice spheres
Authors: Herman B. M. , Battan L. J. 
Published: February 2007

AbstractThunderstorms containing hail have been found to have extremely large radar reflectivities. Experimental work by Atlas, Harper, Ludlam and Macklin (1960) has shown that hailstones may have unexpectedly large back‐scattering cross‐sections. In order to shed additional light on this problem, the normalized back‐scattering cross‐sections (σb) of spherical ice particles with complex index of refraction N = 1·78 – 0–0024i (N = m – mki where m is the ordinary index of refraction, and mk is the Mie absorption coefficient) were calculated from the complete Mie equations. Small intervals of α (= 2πa/λ where a is the radius of the scattering particle and λ is the wavelength of incident radiation) were taken up to a value of 30. The back‐scattering from large ice spheres is shown to be considerably higher than that from water spheres of the same size. In general, the differences between the reflectivities of ice and water spheres increase with increasing α up to an α of about 60.Calculations of (σb) were made for various values of the complex index of refraction in order to better understand the properties of the back‐scattering equations.
Rain in East Africa
Authors: Johnson D. H. 
Published: February 2007

AbstractFor mapping daily rainfall over East Africa, a method is used which emphasizes distribution rather than rainfall amount. Isohyets are unsuitable for synoptic studies.Daily rainfall analyses show large‐scale systems which develop and persist over periods of days. Changes of type continually take place against background seasonal patterns. Day‐to‐day evolutions are frequently untypical of seasonal trends. There is little evidence of mobile features. Patterns do not take the form of zonal bands in preference to other shapes.Statistics describing the scale, structure and persistence of rain areas are given. Regional differences are discussed.
Study of rainfall over Chittagong Coast during 1955
Authors: Rahmatullah M. 
Published: February 2007

AbstractThe rainfall distribution over Chittagong Coast for the year 1955 was studied to determine the importance of ‘heavy’ rainfall of 3 in. or more in the rainfall distribution curve. Chittagong City and Cox's Bazar were taken as representative stations for this study. In 1955, Chittagong City with an annual normal of 108 in., recorded 148 in. of rain. Cox's Bazar, on the other hand, with an annual normal of 140 in. had only 134 in. of rain. Out of the total of 99 rainy days during 1955, the number of heavy rainfall days in Chittagong was only 14, accounting for 57 per cent of the total rainfall of the year. In the case of Cox's Bazar, out of 108 rainy days during 1955, only 10 days recorded heavy rain of 3 in. or more, accounting for about 35 per cent of the total annual rainfall of the year. It was found that the ‘heavy’ rainfall curve is the most important feature determining the pattern of the rainfall distribution curve over Chittagong Coast.
Some ozone‐weather relationships in the middle latitudes of the Southern Hemisphere
Authors: Kulkarni R. N. 
Published: February 2007

AbstractThe paper discusses relationships observed between ozone and the upper‐air measurements made at Brisbane, Aspendale and Macquarie Island. The correlation coefficients between the short‐term fluctuations of ozone and the temperatures at 100, 200 and 300 mb levels at these places are presented. In general, high ozone was observed to be associated with the sinking of the tropopause, descending of stratospheric air, warming of the lower stratosphere and a southerly flow of air in the lower stratosphere. At Macquarie Island, an instance of the ozone fluctuations in the baroclinic waves of the polar night westerly vortex suggested that the middle stratospheric waves contributed to the unexplained long term variance in total ozone.The meteorological parameters at the 200 mb level did not reveal the type of oscillation shown by the spring maximum level of ozone with a periodicity of 24 months. From the study of the 60 mb temperatures, it is concluded that the middle stratospheric circulation is playing an important role in deciding the spring level of ozone in middle latitudes of the Southern Hemisphere.
Accuracy of dew and frost points measured by frost‐point hygrometers
Authors: Grant D. R. 
Published: February 2007

AbstractApparatus has been built at the Meteorological Research Flight to train observers on the ground in the use of frost‐point hygrometers (Brewer, Cwilong and Dobson 1948). Using this equipment the frost point of the air being measured is known accurately, and from readings by a number of observers over the complete range of the instrument an estimate of the root‐mean‐square error of measurement can be made. This error can be broken down into a systematic error and random error, both of which vary with the humidity being measured. The systematic and random errors of the individual observers can also be established.The results show that the r.m.s. error of a dew‐point measurement is about 0·7$C. The r.m.s. error of a frost‐point measurement is 1·0$C at — 40$C increasing to 1·7$C at — 75$C. If the systematic error were eliminated the standard deviation of the random errors would be about 0·6$C for dew points, 0·8$C for frost points of — 40$C and 1·6$C for frost points of — 75$C. The details of the results are given in Tables 1 and 2.
Precipitation from layer cloud
Authors: Stewart J. B. 
Published: February 2007

AbstractEight years of data on layer clouds obtained on aircraft ascents were related to ground observations of precipitation reported by the nearest full synoptic station, and used to investigate the variation in the occurrence of precipitation at the ground with the height of cloud base above the 0°C level and the variation in intensity of precipitation with cloud thickness.It was found that if the base of the layer cloud was more than 1 km above 0°C level there was less than a five per cent chance of precipitation reaching the ground ‐ however thick the cloud was ‐ compared to a nearly 90 per cent chance of precipitation for clouds with bases less than a kilometre above the 0°C level and more than 2 km thick. For layer clouds with their bases below the 0°C level, it was found that 0·4 km was the minimum thickness to give any precipitation and 1 km and 3 km were the respective minimum thicknesses for continuous slight and continuous moderate rain to be produced. A similar analysis was carried out for layers up to 2 km thick wholly below the 0°C level with comparable results. It was also found that at least 60 per cent of precipitating layer clouds of thickness less than 2 km with bases below the 0°C level and unaffected by layers above, gave precipitation by the coalescence process alone.
Determination of ozone amounts by the dobson spectrophotometer using the focused sun method
Authors: Hamilton R. A. 
Published: February 2007

AbstractWhen the effective path length μ is greater than 4 the focused sun method must be used when measuring the amount of atmospheric ozone by the Dobson spectrophotometer. Errors are introduced by light from the sky, and by light scattered within the spectrophotometer. A method of evaluating these errors is described, and corrections are tabulated which enable measurements of ozone amount to be made when μ is in the range 4 to 8·5.
The interpretation of stellar shadow‐bands as a consequence of turbulent mixing
Authors: Townsend A. A. 
Published: February 2007

AbstractRecently published measurements of shadow‐band patterns produced by star‐light at ground level are analysed using the theory of wave‐propagation in a turbulent medium. The measured spatial and time spectra of the patterns can be described quantitatively by assuming that the optical inhomogeneities are produced by turbulent mixing in the earth's boundary‐layer and in shallow layers at heights around 8 km. Characteristics of the assumed turbulence in the upper air are estimated to be: mean height 8 km, layer depth 90–200 m, r.m.s. velocity fluctuation in wind direction 1·5‐2·0 m sec−1, r.m.s. temperature fluctuation 0·2°C.
Some aspects of the large‐scale turbulence and diffusion in the atmosphere
Authors: Kao S.‐K. 
Published: February 2007

AbstractThe Eulerian and Lagrangian autocorrelations and energy spectra of the large‐scale turbulent motion in the atmosphere are computed and analysed. It is found that the distributions of the Eulerian and Lagrangian autocorrelations of the zonal velocities show the characteristic of an exponentially decreasing function, whereas those of the meridional velocities exhibit the behaviour of a sinusoidal function with a damping amplitude. The energy spectra appear to be proportional to the minus second power of the frequency in the high frequencies.Analyses are also made of the energy spectra, autocorrelations, and the Eulerian‐Lagrangian time scale transformation in a planetary wave model. The ratio of the Eulerian and Lagrangian frequencies for the large‐scale atmospheric turbulence is found to be a function of the mean zonal velocity, latitude, and the angular wave number of the planetary wave. Comparisons are made of the energy spectra and autocorrelations derived from the planetary wave model and those found from observations.
Observations of hydrometeor charge evolution in thunderstorms
Authors: Maccready P. B. , Proudfit A. 
Published: February 2007

AbstractSystematic observations were made of hydrometeor charges associated with thunderstorms at Flagstaff, Arizona. The measurements were made from a light aircraft by the standard induced‐charge method, in and below clouds which were entirely supercooled. The aircraft would spiral within the central upcurrent up into the cloud and later spiral down through the precipitation shafts. From these limited cases, a rather consistent picture emerged: (a) generally, charges on graupel and hail within the supercooled clouds were positive (measurements made as high as the −17.5°C level), (b) below the cloud at the + 2° to + 8°C level, just where the melting of the hydrometeors was apparently complete, the hydrometeors became abruptly negative, (c) at still lower, warmer levels the charge magnitudes were consistently smaller, with both signs represented but predominantly negative. The data suggest that a strong hydrometeor charging mechanism is associated with the melting of ice hydrometeors outside the cloud. The maximum charge magnitudes appeared comparable to the amounts which would be limited by breakdown gradients at the hydrometeor surface.
Changes in amounts of sunshine in British Columbia, 1901‐1960
Authors: Powell J. M. 
Published: February 2007

Abstract5‐year running means and 20‐year averages of annual and seasonal sunshine hours for 11 stations in British Columbia having a record of at least 30 years are discussed. In comparison with the period 1921‐40 sunshine hours have been less in all seasons at most stations for the periods 1901‐20 and 1941‐60. Coastal stations had the greatest change during the summer, but inland stations had the greatest change during the winter. All stations recorded the least change in the spring.
Observations of the modification of the microclimate at a leading edge
Authors: Dyer A. J. , Crawford T. V. 
Published: February 2007

AbstractTemperature profiles observed over a heavily irrigated grass field in the midst of dry surroundings show continuous modification up to the maximum height of measurement (5 m) even at a distance of 200 m from the leading edge.Considerable variation of eddy fluxes in the vertical is demonstrated. The surface fluxes are found to undergo gradual adjustment.These observations illustrate that a site of considerable extent is required for micrometeorological and agricultural studies before horizontal uniformity can be assumed.
The divergence of horizontal eddy flux of momentum in the lower equatorial stratosphere
Authors: Tucker G. B. 
Published: February 2007

AbstractEvidence is presented to support the assumption that the divergence of horizontal flux of momentum due to large‐scale eddies has a sinusoidal variation of the same period as, but with a phase difference from, the zonal wind oscillation of approximately 26 months. The phase difference appears to be about μ/2 with the divergence wave preceding the zonal wind wave. The evidence is not regarded as conclusive.
A long‐period recorder for wind speed and direction
Authors: Sumner C. J. 
Published: February 2007

AbstractA description is given of a run of wind and direction‐sensing mechanism for use in conjunction with a battery operated long‐period recorder (Sumner 1959), which records the variables ten times per hour. It is a relatively cheap semi‐portable instrument and is intended for use in remote areas, or as an investigational tool which may be readily moved to new sites.
The limitations of analogues selected from sequences of daily weather types over the British Isles
Authors: Lewis R. P. Waldo , Murray R. 
Published: February 2007

AbstractAn account is given of a numerical experiment in extended period forecasting using analogues selected on the basis of similarity of sequences of daily weather types. The resulting forecasts of weather sequences are significantly better than chance for between 5 and 10 days. This result is probably largely due to persistence.
The photochemical formation of electronically excited oxygen molecules in the atmosphere
Authors: Wayne R. P. 
Published: February 2007

AbstractSpectroscopic studies of the airglow indicate that electronically excited molecular oxygen in the 1Δg and 1Σg+ states is produced in the atmosphere. The way in which the excited states are formed in the atmosphere has been the subject of much speculation, and the present paper attempts to evaluate some of the mechanisms proposed in the light of laboratory experiments.The most probable excitation mechanism for O2 (1Δg) appears to be the primary step in the photolysis of atmospheric ozone:O3 + hν (λ < 3,100 Å) → O2 (1Δg) + (1D).O2 (1Δg+) may then be formed in the energy‐pooling process:O2 (1Δg) + O2 (1Δg) → O2 (1Σg+) + O2 (1Σg−).
Analysis of low‐level, constant volume balloon (tetroon) flights over New York City
Authors: Hass W. A. , Hoecker W. H. , Pack D. H. , Angell J. K. 
Published: February 2007

AbstractConstant volume balloon (tetroon) flights made over New York City at heights of about 300 metres during June of 1965 are analysed. The transponder‐equipped tetroons were tracked to distances exceeding 100 km by means of the wsr‐57 weather radar located in Central Manhattan. On non‐sea breeze days the tetroons tend to move towards low pressure with an angle of 35 degrees, and to move with about two‐thirds of the geostrophic wind speed. There is a correlation of 0.73 between lapse rate and tetroon‐derived r.m.s. vertical velocity, and of 0.43 between lapse rate and Lagrangian period of vertical oscillation. Tetroon‐derived vertical velocities are also used to obtain estimates of the mean Reynolds stress (1.3 dynes cm−2 at flight level) and the downwind variation of vertical diffusion over an urban area.
Variations in the content and flux of water‐vapour over north‐eastern North America during two winter seasons
Authors: Barry R. G. 
Published: February 2007

AbstractAtmospheric water‐vapour content and horizontal flux of water‐vapour are evaluated for twenty stations for November‐February 1956‐;7 and 1957–8. Mean patterns of vapour content and the total and eddy transport between the surface and 500 mb are analysed to show the marked differences between the two seasons. More detailed information is provided by average values of vapour and flux for a number of types of airflow pattern over Labrador‐Ungava.
An objective method for estimating wind‐speed fields from wind‐direction fields
Authors: Mancuso R. L. 
Published: February 2007

AbstractAn objective method is described for obtaining an estimate of the wind‐speed values within the interior of a region when only the streamline field for the region and the wind‐speed values along the boundary are given. The method has been developed and tested for possible use in data‐scarce areas where conventional wind analyses can not be made, but where wind‐direction fields might be derived with reasonable accuracy and detail from satellite cloud photographs. The basic approach consists of computing the wind speeds within the interior of the region by stepping downwind along the streamlines from the known wind‐speed values at the inflow boundary. Divergence is assumed to be constant along each streamline and is determined in a manner such that successive computational cycles minimize the differences between the computed and known wind speeds at the outflow boundary. The testing was conducted using known wind‐velocity fields over the United States and also ATS‐3 cloud‐motion data over the Caribbean. The computed wind‐speed fields were found to be in reasonably good agreement with the actual wind‐speed fields.
An observational study of the energy balance of the stationary disturbances in the atmosphere
Authors: Holopainen E. O. 
Published: February 2007

AbstractDifferent terms in the equations describing the balance of kinetic energy and available potential energy in the so‐called stationary disturbances or standing waves (deviation of the atmosphere's time‐mean flow from axial symmetry) are evaluated approximately by using the observational statistics of the atmospheric flow. Because many simplifications and assumptions have been necessary in order to get estimates of certain terms, the results only give a rough first‐estimate picture about the maintenance of the stationary disturbances.The results indicate that in winter the stationary disturbances are typically baroclinic waves, which get available potential energy from the temperature distribution of the zonally‐averaged mean flow and partly convert it into kinetic energy to offset the destructive effect on the latter by small‐scale turbulent friction, large‐scale transient motions and conversion into zonally‐averaged mean motion. The most important ‘ external ’ forcing seems, from the energy point of view, to be the stationary heat sources and sinks, which in winter destroy the available potential energy of the stationary disturbances; the effect of mountains in the energy balance of the standing waves seems to be relatively minute and actually smaller than the kinematic and thermal effects of large‐scale transient flow systems.In summer the stationary disturbances appear to form a thermally‐driven system, where the frictional loss of kinetic energy is compensated for by a conversion from the available potential energy, which in turn is maintained by generation due to diabatic heating.
The effect of revised collision efficiencies on the growth of cloud droplets by coalescence
Authors: Bartlett J. T. 
Published: February 2007

AbstractThe collection efficiencies of water drops falling in still air have been recalculated by Hocking and Jonas (1970). In this paper these revised values have been used to estimate the rate of production of large droplets (r > 30 μm) by coalescence. It is found that there is an increase in the rate of production of droplets with radii of about 20 to 25 μm compared with the rate calculated using Hocking's earlier (1959) values, but generally a decrease in the rate of production of droplets with radii 20 to 25 μm. It is also shown that neglecting the small, but finite, collection efficiencies predicted for droplets with radii less than about 15 μm has negligible effect on the rate of production of larger droplets.
A note on the dependence of atmospheric predictability on baroclinic development
Authors: Everson P. J. , Davies D. R. 
Published: February 2007

AbstractA two‐level, quasi‐geostrophic model, described by Everson and Davies (1970), is used to study the dependence of duration of predictability (as defined by, e.g., Charney et al. 1966) on the phase, at some initial time in the integration, of global scale baroclinic development (expressed in the model in terms of fluctuations in eddy kinetic energy, K').Using firstly an invariable subgrid scale coefficient in a control run of 120 days, sinusoidal perturbations, wave length approximately 6,000 km, of the geopotential heights are inserted at all the grid points at (a) day 72, corresponding to a maximum in model K', and (b) day 84, corresponding to a minimum in model K'. The consequent ‘perturbed’ integrations are compared to the control values by taking the r.m.s. of the difference in the 500 mb calculated temperature distributions, and determining the time taken for this to increase to the ‘persistence’ value, i.e. the maximum r.m.s. difference between two randomly selected model states. The doubling time of error in (a) was seen to be 12 days leading to a model predictability of 24 days, and in (b) it was seen to be 17 days, leading to a predictability of 34 days: these values are related to an initial perturbation amplitude of 1°C.These experiments were then repeated using a variable subgrid scale coefficient, depending on grid scale horizontal temperature gradient as described by Everson and Davies (1970). The results were; (a) working from a day of maximum K', the doubling time of error was reduced to 8 days, approaching the value obtained by primitive equation numerical models and corresponding to a predictability of 16 days; (b) working from a day of minimum K', the doubling time of error was 13 days, corresponding to a predictability of 26 days. The results in both cases show that predictability, as calculated from some initial phase of baroclinic development, is 50 per cent higher as measured from a maximum in K'compared with a minimum in K'. It also drops sharply with increase in the degree of model sophistication (expressed in the system discussed in this paper as variability of the subgrid scale coefficient).
A wind tunnel investigation of collection kernels for small water drops in air
Authors: Beard K. V. , Pruppacher H. R. 
Published: February 2007

AbstractThe rate at which small water drops grow by collision and coalescence has been investigated experimentally by means of a wind tunnel constructed for cloud physics research. Individual water drops of radii 70 < A <300μ were freely suspended in the tunnel airstream carrying a continuous water cloud with droplets of radii 2 < a < 8μ and with a liquid water content between 0.8 and 1.2 g m−3. The rate at which the suspended water drops were growing by collision and coalescence was determined as a function of the drop size of the suspended drop, the liquid water content of the cloud and the size distribution of the drops in the cloud. From the observed parameters, specific collision kernels were computed and compared with those derived from theoretical and experimental collision efficiencies reported in literature. The results show that for p = a/A <0.1, i.e. for large cloud drops growing by collision with small cloud drops, it is justified to compute the growth rate of cloud drops of A < 136μ on the basis of the theoretical collision efficiencies of Shafrir and Neiburger as given analytically by Berry, and the growth rate of cloud drops of A > 136μ on the basis of the theoretical collision efficiencies given by Mason.