bluuebunny/crossref_metadata_2025_split huggingface dataset:
Some fog droplet size distributions obtained by an impaction method
Authors: Garland J. A. 
Published: February 2007

AbstractA cascade impactor technique based on the methods of previous workers has been used to study the size distribution of water droplets in several fogs. Nomarski interference contrast, used as a method of microscopic examination of the samples revealed large numbers of small droplets which were not visible under phase contrast. In about one third of the fogs studied these droplets, smaller than 2 μm diameter, made a large contribution to the optical extinction coefficient. The use of interference contrast for assessment of samples has resulted in some reduction of the large deficit, frequently found by previous workers, in the extinction coefficient calculated from the droplet size distribution, as compared with that measured optically. The remaining discrepancy, however, is significant and sometimes exceeds a factor of two.The small droplets are probably the result of condensation of water on hygroscopic nuclei whose critical supersaturation has not been exceeded. Their implications regarding the rate of clearance of fog are considered.
Wind profiles in and above a forest canopy
Authors: Oliver H. R. 
Published: February 2007

AbstractUsing an on‐line computer, measurements were made of wind speeds in and above a pine forest together with accurate potential temperature profiles over a wide range of stability conditions. It was found that between values of Richardson number of approximately –0.05 and +0.10 the wind profile above the canopy followed a pure log form with the measured roughness length increasing linearly from 0.75 to 1.23 m respectively. Outside this stability range a log‐linear profile could be fitted. The shape of the wind profile within the canopy was determined, and an increase of wind speed within the trunk space was noted.A preliminary experiment to determine the effect of the anemometer tower structure upon wind speed readings is also described.
Eddy kinetic energy spectra in the Middle East sub‐tropical and easterly tropical jet streams
Authors: Gordon A. H. 
Published: February 2007

AbstractAn analysis is carried out of samples of time series of observations of wind components of the winter sub‐tropical and summer easterly jet streams in the Middle East. The periods covered by the samples are 60 days. Individual components showed peaks in the eddy kinetic energy with minimum periods of about 4 days. However, when both u and v components are combined or two separate 60 day samples are combined marked peaks diminish. There is probably a spectrum of preferred peak periods which can only be identified if a much larger population of individual series is analysed.
Aerodynamic properties of a plant of complex structure
Authors: Landsberg J. J. , Thom A. S. 
Published: February 2007

AbstractCoefficients of momentum and vapour transfer of spruce shoots in a wind‐tunnel are measured, and are shown to depend on shoot density: transfer per unit needle area becomes less effective as shoot density increases. Comparisons with theoretical values derived from established coefficients for 1 mm and 3 mm diameter cylinders (representing needles and twigs, respectively) indicate that the magnitude of the implied shelter effect is the same for water vapour as for momentum.
On the dispersion of the sizes of droplets growing by condensation in turbulent clouds
Authors: Bartlett J. T. , Jonas P. R. 
Published: February 2007

AbstractThe effect of turbulence within a cloud on the distribution of the sizes of droplets growing by condensation has been examined in some detail with the aid of a scheme for simulating a fluctuating updraught numerically. It is found that, contrary to the conclusions previously reached by some Russian and Chinese workers, the spread in the radii of droplets at any given level which this mechanism produces is very small (generally < 0.2 γm). This result agrees with the conclusion of a similar analysis carried out by Warner.Other factors which may account for the observed distributions of droplet sizes have been considered and the most important appear to be mixing between a cloud and its environment and the variable composition of condensation nuclei. It also appears that the absorption of organic surface active substances on to some condensation nuclei probably accounts for the existence of small droplets in the interiors of well‐developed clouds.
Ekman boundary layer interactions in a numerical model of the general circulation
Authors: Everson P. J. , Davies D. R. 
Published: February 2007

AbstractA representation of an ‘Ekman’ type of boundary layer (assumed to extend from 1,000 mb to 900 mb) is inserted into a two‐level, quasi‐geostrophic, general circulation numerical model. An approximate time‐dependent analytic solution of this boundary layer is matched to the ‘free atmosphere’ régime of the model through the vertical velocities produced at the grid points. By using this analytic solution the essential physical characteristic of the observed continuous increase with height of scale length of turbulence in the boundary layer is represented. By comparing time integrations of two models, only one of which contains an Ekman layer, it is shown that large‐scale flow characteristics, expressed in terms of growth rate of zonal and eddy kinetic energy, are sensitively dependent on the presence of such a layer in a numerical model.
Studies of turbulence in the surface layer over water (Lough Neagh). Part I. Instrumentation, programme, profiles
Authors: Sheppard P. A. , Tribble D. T. , Garratt J. R. 
Published: February 2007

AbstractInstrumentation is described which has been used over a body of deep water, with fetches of 8 km to 22 km, to provide (i) vertical profiles of mean wind u, potential temperature ø and specific humidity q from the water surface to 16 m height and (ii) turbulent fluctuations of temperature and of the longitudinal and vertical components of wind and hence the vertical fluxes of momentum and sensible heat.Logarithmic wind profiles in near‐neutral conditions lead to a drag‐coefficient CD of the water surface as a function of the wind speed u10 at 10 m height given by 103 CD = 0.36 + 0.10u10 (3 m s−1 < u10 < 16 m s−1). Corresponding bulk transfer coefficients for heat and water vapour are not distinguishably different from CD in the observed range of u*z0/ν < 102 (conventional nomenclature).An analysis, following Webb (1970), of profiles in stable conditions (0 < Ri4 ≤ 0.16) lends support to the utility of the log‐linear form. Using the Monin‐Oboukhov relation ∂X/∂z = X*ø (z/L)/(kz) where × is either u, ø, or q and taking ø(z/L) = 1 + α z/L, so that z/L = Ri/(1− α Ri), we find α ≃ 6. In unstable conditions (0 > Ri4 ≥ −0.6) the profile shape factor Sx = (X4 − X1)/(X16 − X1) is greater for ø than for u, implying øH < øM (KH > KM) but Sq has less well defined behaviour. The data on Su,ø are not inconsistent with øM = (1 − 16 z/L)−1/4, øH = ø, as proposed by Dyer and Hicks (1970) and others but the shape factor is very insensitive to the numerical factor multiplying z/L in these relations.Analysis of the measurements of turbulent fluctuations and derived fluxes will be presented in later papers.
The variability of the onset of spring in Britain
Authors: Davis N. E. 
Published: February 2007

AbstractThe first day of spring is defined in terms of daily maximum temperatures. Spring at Oxford as defined begins some time between the third week of February and the last week of April. The average date shows a secular change over the last hundred years.The date of the first day of spring is shown to be related to ice conditions in the Baltic and in the Iceland area, to the sea temperature pattern in the North Atlantic, the circulation patterns at 500 mb and to various atmospheric indices. Rules developed from these relationships enable ‘statistical’ forecasts for the first day of spring to be made.
The estimation of ground‐level pressure fields from computer analyses and their application to large‐scale atmospheric mass transfer
Authors: Lewis R. P. W. 
Published: February 2007

AbstractA method is presented for estimating mean ground‐level pressure over most of the Northern Hemisphere using objectively analysed fields of 1,000 mb and 500 mb height together with suitable grid‐point values of mean topographic height. A limited sample of data indicates that estimates of the seasonal transfer of mass between the Hemispheres using fields of mean sea‐level pressure are too large by a factor of about 4.
Zonal wind quasi‐biennial oscillations at 25–60 km altitude, 1962–69
Authors: Groves G. V. 
Published: February 2007

AbstractMeteorological rocket observations of zonal winds at thirteen sites (or pairs of sites) have been analysed for amplitudes and phases of their quasi‐biennial oscillation. The period of the oscillation was taken to be 32 months because from 1962–69 the period was relatively constant, not varying by more than ±3 months. Amplitudes and phases of the oscillation over a wide range of latitude are presented and discussed. The low‐latitude part of the oscillation is well‐defined with maximum amplitudes at 25 to 30 km altitude, which reach about 25 ms−1 at the Equator and decrease to a few ms−1 at 20° latitude. At other latitudes, amplitudes are less than 5 ms−1 except above 50 km at two sites between 50° and 60° latitude, where another main part of the oscillation is indicated. More observations and sites are needed at mid and high latitudes. Observations at the highest latitude site (77°) show no evidence of a diminished amplitude. Phases also depend on height and latitude and may reach gradients of 1 month km−1 with height and 2 months deg−1 with latitude respectively.
Air motion within Kelvin‐Helmholtz billows determined from simultaneous Doppler radar and aircraft measurements
Authors: Browning K. A. , Bryant G. W. , Starr J. R. , Axford D. N. 
Published: February 2007

AbstractA new linked mode of operation has been used to obtain virtually simultaneous measurements by a fully instrumented aircraft and a ground‐based high power radar within a train of large amplitude Kelvin‐Helmholtz billows in the optically clear atmosphere. Both sets of data were analysed to show the detailed distribution of air motion and turbulence within the billows. The resulting pattern was consistent with a train of vortices each of which was characterized by a vertical wind shear of 6 m s−1 over 100 m, with downward motion of about 1 m s−1 on the downshear side and upward motion of about 1 m s−1 on the upshear side. Between the vortices the vertical shear decreased to almost half the maximum value. The most intense radar echoes occurred within inclined layers connecting the top of one region of maximum vorticity to the bottom of the next. The aircraft, which flew through the upper parts of the billows, encountered turbulence of up to moderate intensity as it penetrated the crests of the billows. Between successive penetrations of the billow crests the aircraft flew close to but just above the region of intense radar echo and encountered smooth air with a slowly varying vertical component of motion.
Coalescence in a weakly turbulent cloud
Authors: Tennekes H. , Woods J. D. 
Published: February 2007

AbstractIn a recent paper on the effect of turbulence on droplet collisions in clouds, Woods, Drake and Goldsmith (1972) proposed that the principal factor was the strong spectral peak of shear near the Kolmogoroff micro‐scale. This hypothesis led to an important simplification, namely that spatial and temporal fluctuations in the turbulent shear field could be ignored during an encounter between a pair of cloud droplets. However, the authors pointed out that their simple model of (isotropic, homogeneous) turbulence contained an assumption, namely that the shears are normally distributed, which would have to be re‐examined if it turned out that droplet collision efficiency increased rapidly after a threshold value is exceeded. Subsequent measurements by Jonas and Goldsmith (1972) showed that this is indeed the case. In this paper we reconsider the efficiency of turbulent coalescence in the light of the new experimental data, and taking account of the intermittency of shear distribution. It is concluded that significant increases of collection efficiency will occur in clouds which are only weakly turbulent. For example, the collection efficiency for droplets of radii R = 20 μm and γ = 9 μm in a cloud with energy dissipation rate ε = 55·5 cm2 s−3 will be approximately 14 per cent compared with 2 per cent for the same droplets falling though still air. The shear zone in the wind tunnel experiment designed by Woods et al. (1972) is a realistic approximation to the shear zones in cloud turbulence.
The production of secondary ice particles during riming
Authors: Mossop S. C. , Brownscombe J. L. , Collins G. J. 
Published: February 2007

AbstractTwo series of experiments were undertaken to investigate whether secondary ice particles are thrown off during the accretion of supercooled water drops upon an ice surface. Riming took place in cloud at a temperature of about −9°C, and the accreted droplets were of various diameters up to 100 μm. Drops were accreted upon targets moving at velocities from 0·15 to 2·1 m s−1. The number of secondary ice particles produced per unit mass of rime appears to be far too low to account for the high concentrations of ice particles observed in some natural clouds.Footnote added in proof. Subsequent work by J. Hallett and S. C. Mossop (Nature, 1974, 249, pp. 26‐27) has shown that high concentration of secondary ice particles can be produced by riming under certain special conditions.
Storm surges in the Bay of Bengal
Authors: Das P. K. , Sinha M. C. , Balasubramanyam V. 
Published: February 2007

AbstractEstimates of the surge generated by a model storm impinging on three coastal areas of north Bay of Bengal are presented. A linear shallow‐water long‐wave model was used to evaluate the surge. Surge amplitudes were computed for different values of storm intensity and speed. The effect of the astronomical tide was estimated by specifying initial boundary conditions on the open boundary of the computational grid. For a devastating storm, which struck Bangladesh (formerly East Pakistan) on 12/13 November 1970, we show that superposition of the surge on the tide leads to an overestimate of sea level elevation at the time of landfall.
Electrical conditions near the bases of thunderclouds over New Mexico
Authors: Rust W. D. , Moore C. B. 
Published: February 2007

AbstractMeasurements of atmospheric electricity were made at a mountain‐top observatory with some instruments at the earth's surface and with others carried aloft by captive balloons into the bases of thunderclouds overhead. The properties measured included the charge on individual precipitation particles, the electric current density carried by precipitation, the local electric field vector, and the electrical conductivity of the air.The electric fields aloft, near cloud base, were often twice the intensity of the surface fields and had large horizontal components that indicated non‐uniform distributions of charge. The polar electrical conductivity of cloudy air was found to be about 2 times; 10−15 per ohm m which is about 1/10 that of the clear air at the same altitude.The polarity of charge on the precipitation aloft was almost invariably that of the local potential gradient; it did not show the well‐known ‘mirror‐image’ relation that is observed between the precipitation electricity at the ground and the local potential gradient during periods of point discharge. Use of our charge and conductivity data in Wormell's analysis of Wilson's ion capture mechanism suggests that ion capture in the subcloud region may explain adequately the precipitation charge arriving at the earth.There was little correlation between the magnitudes of the precipitation charge aloft and the intensity of the electric field. We could not identify the origin of the charges found on precipitation aloft although one possible explanation is that they were derived from that residing on the cloud droplets from which the raindrops were formed.Calculations of the electrical power transfer in the lower regions of developing thunderclouds by the fall of charged precipitation indicate local energy dissipation as predicted by Vonnegut, with rates of about 5 times; 10−6 watts m−3.
The mean meridional temperature behaviour of the stratosphere from November 1970 to November 1971 derived from measurements by the Selective Chopper Radiometer on Nimbus IV
Authors: Barnett J. J. 
Published: February 2007

AbstractZonal means of radiance originating in the stratosphere and measured by the Selective Chopper Radiometer are given for the period November 1970 to November 1971. Results are presented as latitude‐time sections and as monthly means. Equatorial cooling of several degrees was found to be associated with a major warming in the Northern Hemisphere. In the lower stratosphere the annual variation of temperature near the South Pole was approximately twice that near the North Pole, but in the upper stratosphere the variations were almost equal. At the Equator a semi‐annual oscillation of 2.5 K amplitude was present near the stratopause, while there was an annual oscillation of 1.7 K near the tropopause. Global mean temperatures exhibited little variation but the annual component for the upper stratosphere was consistent with the variation of solar heating. The upper stratosphere of the Southern Hemisphere had a pole warmer than midlatitudes during most of the winter, unlike the Northern Hemisphere winter. Height‐latitude sections of retrieved temperature are given for days representative of each season.
Sponginess in ice grown by accretion
Authors: Roos D. V. D. S. , Pum H.‐D. R. 
Published: February 2007

AbstractIce was grown by accretion on rotating embryos at air temperatures of −6, −12 and −24°C while the liquid water content ranged approximately between 1 and 4 g m−3. The air speed in the wind tunnel and the modal droplet diameter were, respectively, 20 m s−1 and 13 μm. Details of the structure of the spongy ice were studied in thin sections after elimination of internal liquid water by centrifuging. Sponginess occurred in radial zones associated with surface protuberances but did not necessarily coincide with the indentations between them. Radial striations and tangential microlayers of some 200 μm thickness were found and point to a complex original ice‐water interface. About half of the spongy specimens were allowed to freeze undisturbed. The subsequent transparent ice contained patches of air bubbles mostly of some 20 μm in diameter showing distinctive arrangements and a log‐normal size distribution. Crystals were elongated in the growth direction while optic axes tended to lie normal to it, 67° being the average value of the angle between the projection of the c‐axis on the plane of the hailstone section and the growth direction. This tendency confirms epitaxial growth during the later stages of freezing.
Determination of optical parameters of atmospheric particulates from ground‐based polarimeter measurements
Authors: Kuriyan J. G. , Phillips D. H. , Willson R. C. 
Published: February 2007

AbstractThis paper describes the theoretical analysis that is required to infer, from polarimeter measurements of skylight, the size distribution, refractive index and abundance of particulates in the atmosphere. To illustrate the viability of the method, some data obtained at UCLA is analysed and the atmospheric parameters are derived. The explicit demonstration of the redundancy in the description of aerosol distributions suggests that radiation field measurements will not uniquely determine the modal radius of the size distribution. In spite of this non‐uniqueness information useful to heat budget calculations can be derived.
What property of a haze is determined by light scattering?
Authors: McKellar Bruce H. J. 
Published: February 2007

AbstractWe develop a criterion for estimating the conditions under which two polydisperse hazes will give identical scattering of light in the single scattering approximation. This criterion, that equivalent hazes have the one value of the parameter p2 = R8/R6, is derived from the Rayleigh‐Gans approximation to small angle scattering. We find that it is well satisfied by hazes which have been found to give identical scattering.
Long‐wave radiation at the ground. II. Geometry of interception by slopes, solids, and obstructed planes
Authors: Unsworth M. H. 
Published: February 2007

AbstractAt the earth's surface, long‐wave radiation received from the atmosphere in the absence of cloud may be expressed as the sum of the flux density from an isotropic source and the flux density due to anisotropy of atmospheric radiation. Separation of these components facilitates calculations of the radiative flux received by obstructed horizontal surfaces (near walls or in valleys), by sloping planes, by solid cylinders, and by spheres and prisms. Radiation received from adjacent surfaces is also considered.As the angular distribution of radiation is the same for overcast skies as for clear skies, the relationships for clear skies may be extended to derive climatological mean values for the long‐wave irradiances of slopes, solids, etc.
A quasi‐biennial standing wave in the Southern Hemisphere and interrelations with sea surface temperature
Authors: Trenberth Kevin E. 
Published: February 2007

AbstractAn empirical orthogonal function analysis is performed on monthly mean sea level pressure (SLP) deviations from normal (anomalies) in the Australasian area and monthly mean sea surface temperature (SST) anomalies in the Tasman Sea for 14 years of data.Only the five components of each that explain most of the variance appear to be significant. Spectral and cross‐spectral analysis of the time series of the coefficients reveals significant relations at a quasi‐biennial periodicity. An empirical model of the SLP and SST fields for this period is constructed and the amplitudes of the oscillation are found to be about 2 1/2 mb in the monthly mean SLP anomaly field and 0·4 degC in the monthly mean SST anomaly field. Physical and statistical indications are that the SST field is largely caused by the SLP field but some interdependence is present.The quasi‐biennial SLP oscillation is related to Pittock's L‐index and appears to correspond to a change in wavenumber 3 in the Southern Hemisphere atmospheric circulation. A phase change occurred at the end of 1970, but in even years prior to 1971, and in odd years since 1970, there were increased meridional transports throughout the troposphere and lower stratosphere by the large‐scale eddies. A suggestion is made that changes in land–sea heating contrasts may be an important part of the mechanism.