bluuebunny/crossref_metadata_2025_split huggingface dataset:
Short‐range vertical diffusion in stable conditions
Authors: Thompson N. 
Published: February 2007

AbstractExperiments have been carried out to determine vertical diffusion in stable conditions at distances of 100 or 200 m from a continuous cross‐wind line source. Simultaneous measurements of vertical turbulence provide the opportunity to test an empirical method of estimating diffusion from wind fluctuation measurements, based essentially on the ideas of Hay and Pasquill (1959), but also attempting to take into account the variation of turbulence with height. The results suggest a fairly systematic variation with stability of the ratio of the Lagrangian and Eulerian scales of turbulence, from values of about two in near neutral stability, to at least ten in rather stable conditions.
Atmospheric pressure waves from the Japanese earthquake on 16 June 1964
Authors: Bowman G. G. , Shrestha K. L. 
Published: February 2007

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

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

AbstractThe distribution of radiative cooling in the vicinity of a temperature inversion in the middle troposphere is calculated for several distributions of humidity. When mixing ratios are high throughout the inversion radiative cooling acts to erode the inversion (minimum cooling at the base, maximum cooling at the top). When mixing ratio decreases rapidly upward from the inversion base most of the inversion is a region of reduced cooling, while maximum cooling amounting to several degrees per day occurs in the vicinity of the inversion base. The region immediately below the inversion base is subject to strong radiative destabilization.Verification of the theoretical cooling rates is sought in ten radiometer‐sonde ascents at Tucson, Arizona. The radiometer‐sonde is only marginally applicable to determining the radiative cooling distribution in the vicinity of the inversions, and random radiometer‐sonde errors and consequences of slant ascent are examined in detail.The radiometer‐sonde measurements, when averaged, verify that radiative cooling is so distributed as to tend to maintain the inversion, showing maximum cooling of the order of 2°C day−1 at and below the base and minimum cooling of the order of 1°C day−1 in the upper part of the inversion. No verification was found for the theoretical destabilization of the layer below the inversion base, although errors and scatter of measurements obscure the true distribution.All ten radiometer‐sonde ascents also penetrated the tropopause, and warming or minimum cooling was found at or very near the tropopause in every ascent. Hence the tropopause must be maintained by processes other than radiation.
The role of wind shear in horizontal diffusion of ambient particles
Authors: Smith F. B. 
Published: February 2007

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

AbstractMeasurements of the total downward emission from the earth's atmosphere in the region 5.5 to 8 μ have been made to heights around 30 km using a balloon‐borne radiometer. The instrument employs a liquid‐air cooled detector of gold‐doped germanium, the responsivity of which increases with height, enabling measurements to be made over about four orders of magnitude. An all‐up weight of 2.5 kg allows the apparatus to be carried on a conventional radiosonde balloon.A method has been devised for interpreting ascent data in terms of the distribution of atmospheric water vapour. The analysis of an ascent made in September 1963 is described in detail. Results are presented which indicate stratospheric mixing‐ratios in the region of 3 × 10−6 g g−1 at least up to 25 km. A large downward flux of radiation observed at the highest altitude was interpreted as emission from sources other than water vapour.
The effect of electric charges upon collisions between equal‐size water drops in air
Authors: Woods J. D. 
Published: February 2007

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

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

AbstractSwinbank's observations at Kerang (February 1962) are used to estimate the variation with the stability parameter ζ(≡ z/L) of the Monin‐Obukhov universal function φM (≡ u,∗︁−1 kz δu/δz).A plot of Ri against ζ is used to derive the approximate variation of α (≡ φM/φH = KH/KM) with ζ.
An experimental study in micro‐meteorology
Authors: Swinbank W. C. , Dyer A. J. 
Published: February 2007

AbstractA description is presented of the experimental techniques used on four micrometeorological expeditions. The instrumentation was designed to provide half‐hourly mean values of wind speed, temperature and humidity at a number of levels up to 16 metres, and of the vertical fluxes of heat, water vapour, net radiation and sensible heat into the ground. The observational material is to be published separately.Analysis of the observations, all for the unstable case, shows close similarity between the turbulent transfer processes for heat and water vapour over the whole range of stability represented by the measurements. Both are more strongly influenced by instability than the exchange of momentum, the difference in behaviour becoming more marked with increasing instability. It is suggested that the similarity between heat and water vapour transfer is due to a correlation between the temperature and specific humidity of the air which originates at the evaporating surface.
A criticism of Bernstein's new dimensional approach to the flux‐gradient relationships near the ground
Authors: Calder K. L. 
Published: February 2007

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

AbstractA short review of the photochemical theory in a ‘dry’ atmosphere is given. It is shown that the difference between theory and observations concerning the vertical gradient of n3 (molecules of ozone/cm3) in the upper stratosphere, where photochemical equilibrium may be assumed, can hardly be accounted for by observational uncertainties. It seems, however, not impossible to reconcile theory and observations by parametric adjustment.A semi‐quantitative theory of ozone in a ‘wet’ stratosphere is developed and the relative importance of different types of reactions is discussed. No reliable quantitative conclusion can be drawn at present due to large uncertainties in a number of parameters. In comparing vertical ozone distribution from this theory with observational data and considering the resulting change in relaxation times compared to the ‘classical’ theory, it is concluded that the influence of reactions of O and O3 with active hydrogen compounds cannot be as strong as that derived from the use of Hunt's reaction rates.
Concerning the existence of Taylor columns in atmospheres
Authors: Stone P. H. , Baker D. J. 
Published: February 2007

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

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

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

AbstractAn analysis is made of the Monin‐Obukhov function ΦM in the familiar wind profile equation, using data from two recent expeditions to Gurley (New South Wales) and Hay (New South Wales). In one, the friction velocity u* is determined directly by the eddy correlation method, and in the other, conducted during mid‐winter when small heat‐fluxes were experienced, by the use of a friction coefficient applied to a low‐level wind.By collating with a similar earlier analysis for heat and water vapour transfer, the variations of ΦM, ΦH and ΦW with stability are presented in tabular form in the z/L range − 0.01 to − 1.0. Within this range the empirical relationships ΦM = (1 − 16 z/L)−1/4 and ΦH, W = (1 − 16 z/L)−1/2, and the implied equality between Ri and z/L, are found to approximate the data to within a few per cent.
An experimental study of Reynolds stress and heat flux in the atmospheric surface layer
Authors: Haugen D. A. , Kaimal J. C. , Bradley E. F. 
Published: February 2007

AbstractThe paper describes an experimental programme to study the characteristics of momentum and heat transport in the first 22‐6 m of the atmosphere. Sonic anemometers and fine platinum wire thermometers were used for flux computations by the eddy correlation technique. Two drag plates were used to measure the surface stress.The results indicate that the fluxes are constant with height to within ± 20 per cent provided a long enough averaging period is chosen. Shorter averaging periods (15 min or less) show considerable variation in the fluxes and in their vertical gradients especially during unstable conditions. It appears that much of this variability can be attributed to the strong effect on the fluxes of submesoscale circulations. The momentum flux gradient seems to be particularly sensitive to these circulations.The most consistent estimates of u* were obtained from the drag plates. They show much less scatter when used in similarity relationships than estimates obtained from the eddy correlation technique at higher levels. However, because of inherent difficulties in installing the drag plates in such a rough surface, their absolute reading was obtained by calibration against the eddy correlation measurement.The correlation γUW, between the longitudinal and vertical components of the wind, is generally much smaller than γWT, the correlation between the vertical component and temperature. With increasing instability γWT increases to a value of about 0‐6 while γUW drops to negligible levels.
Identification of preferred areas of shower development by means of high power radar
Authors: Harrold T. W. , Browning K. A. 
Published: February 2007

AbstractA high‐power, high‐gain radar has been used to investigate clear air echoes on days when surface heating produced low‐level convection. The echoes were from irregular refractive index gradients produced primarily by gradients of water vapour density of small scale (5 cm). It was observed that the height to which the convection extended was revealed by an almost continuous layer of echo. This layer was perturbed on a scale of kilometres by individual convective elements; in addition Areas of Deeper Convection (termed ADCs) some tens of kilometres across occurred. These features are described in this paper. Individual ADCs were identifiable as entities for several hours, and, on the one occasion when reliable movements could be determined, they travelled with the low‐level wind. When the vertical structure of the atmosphere was such that showers occurred, they developed only within ADCs. Evidently the showers occurred in clusters because of the pre‐existing structure of the convective layer and not because individual showers modified their near environment.On two of the four occasions studied the ADCs could be related directly to topographical features. In one case of negligible wind an ADC developed and remained close to hills; on another occasion a plume‐like area of deeper convection over 100 km long appeared to stream away from high ground. More generally, however, advection of ADCs masked possible topographical influences.It is suggested that by using a high power radar to identify ADCs it may be possible to forecast the location of outbreaks of showers and thunderstorms more precisely than is possible at present. Further lines of research are also proposed.
Mechanisms influencing the distribution of precipitation within baroclinic disturbances
Authors: Harrold T. W. 
Published: February 2007

AbstractAn analysis of the flow within baroclinic disturbances over and near the British Isles is made assuming that the wet bulb potential temperature (θw is a conserved property of the flow. Conservation of mass and, when the flow is dry, of mixing ratio, are also used as constraints in the analysis. A model of the flows significant for the production and distribution of precipitation is derived. It is shown that most of the precipitation reaching the surface initially forms within a single well‐defined flow, labelled the ‘conveyor‐belt’ which is typically a few hundred km wide and a few km deep and which flows parallel to and immediately ahead of the surface cold front. The speed of ascent above the warm frontal zone is of the order of 10 cm s−1. Ascent often begins within the warm sector so that there is no well‐marked discontinuity between the precipitation within the warm sector and that in advance of the surface warm front. This flow has been identified as the most significant flow producing widespread precipitation in a variety of synoptic situations, including some which would be analysed conventionally as non‐frontal.Potential instability is continually generated by differential advection in advance of the cold front as a result of over‐running of the low level flow by mid‐tropospheric air of lower θw. The instability is gradually released as the low‐level flow ascends. The leading edge of the warm‐frontal precipitation at the surface is eroded by the evaporation within a descending flow beneath the warm‐frontal zone. When the melting level is low, or the air entering the system on its forward side is dry, the evaporation causes the width of the area of precipitation at the surface to be several hundred km less than that aloft. Some of the moisture which is evaporated is eventually re‐precipitated farther north as the air ascends close to the surface warm front.The mesoscale variability of the airflow within the large‐scale flow modifies the distribution of precipitation. Various structures which have been identified in many studies are summarized and a model of the mesoscale airflow within the conveyor belt is deduced.
Measurements and interpretation of the polarization of radiation emerging from the atmosphere at an altitude of 28 km over South—Western New Mexico (USA)
Authors: Rao C. R. Nagaraja , Takashima T. , Toolin R. B. 
Published: February 2007

AbstractThe degree of linear polarization of the upward radiation emerging from the atmosphere at an altitude of 28 km was measured over south‐western New Mexico (USA) with a balloon‐borne photoelectric polarimeter. Measurements were made in four spectral intervals (bandwidth ∼ 15 nm) centred on λλ362, 401, 501 and 599 nm. The objective was to estimate the turbidity factors of simple, homogeneous models of turbid atmospheres from a comparison of the experimental results with computed values of the polarization of the radiation emerging from the top of the model atmospheres. The computations were based on the solution of the radiative transfer problem in a homogeneous turbid atmosphere. The ‘doubling’ method was used to obtain the solution. It is found that the optimal values of the turbidity factors required to establish good agreement between theory and experiment vary directly as the phase function asymmetry factors associated with the two types of aerosols used in the models. The uncertainty in the interpretation of the polarization data due to the similar effects that the atmospheric aerosols and the unpolarized part of the radiation reflected by the ground have on the polarization of the scattered radiation is briefly discussed.
Some comparisons between observed wind profiles at Risø and theoretical predictions for flow over inhomogeneous terrain
Authors: Petersen E. L. , Taylor P. A. 
Published: February 2007

AbstractVelocity profiles observed in near neutral conditions at the Risø 125 m tower are presented. The upwind terrain contains, depending on wind direction, either one or two distinct changes in surface roughness.Comparisons are made between the observed profiles and those predicted using models based on mixing‐length theory, and, in the case of a single roughness change, the turbulent energy equation. Comparisons with the mixing‐length model are moderately good but some features of the observed profiles are missing from the theoretical predictions. The particular turbulent energy equation model used appears to give slightly less accurate predictions than the mixing‐length model.
Radiative properties of terrestrial clouds at visible and infra‐red thermal window wavelengths
Authors: Hunt G. E. 
Published: February 2007

AbstractA detailed theoretical study of the radiative properties of water droplet and ice clouds at visible and infra‐red wavelengths of 2·3, 3·5, 3·8 and 8·5 and 11 μm is presented. The radiative transfer computations have used a model atmosphere in which the microphysical properties of the clouds have been accurately incorporated. A range of physically realistic size distributions for the cloud particles have been used. The results have been presented in the form of tables of the emissivity, reflectivity and transmissivity, and their equivalent fluxes, at a particular wavelength, as a function of the optical thickness of the cloud layer. A simple scaling relationship enables these extensive tables to be used for any water content of the cloud layers. The results provide a detailed understanding of the radiative properties of terrestrial clouds at thermal infra‐red window wavelengths.The theoretical results are used to interpret infra‐red observations of stratocumulus and cirrus clouds.