bluuebunny/crossref_metadata_2025_split huggingface dataset:
The southern westerlies: A preliminary survey; main characteristics and apparent associations
Authors: Lamb H. H. 
Published: February 2007

AbstractProvisional figures can now be given for the ratio of momentum in the southern circumpolar westerlies to the momentum of the better known northern system. This ratio appears to be 1·5, or rather more, over the year as a whole and rises to over 4 in the northern summer‐southern winter.The preponderance of the southern system is such that it may be regarded as the ‘flywheel’ of the general atmospheric circulation and there are indications that changes in the southern westerlies entail world‐wide adjustments.Preliminary survey at the 500 mb level shows the main trough south of 40°S centred about 100°–110°E at most seasons of the year and the principal ridge in the neighbourhood of the outer reaches of the Ross Sea. The mean troughs and ridges have notably smaller amplitude than in the northern hemisphere. Control of trough and ridge positions appears to be thermal rather than orographic, associated with the position of the broadest part of the Antarctic cooling surface. Little seasonal movement of the troughs and ridges in longitude is discerned and no very great change of circulation intensity, but there is an intensification of flow and increase of amplitude in the Indian Ocean trough from summer to late winter.The pattern of glaciation, as well as available data on depression tracks and anticyclone distribution over the Southern Ocean, support the pattern of ridges and troughs at 500 mb here described and throw light upon the occurrence of blocking in various sectors of the southern hemisphere.This study suggests that it may be the momentum and energy of the southern westerlies which are ultimately responsible for maintaining the meteorological equator on average north of the geographical equator, at least over the oceans.In any climatic epoch when the southern westerlies were (i) farther south than now, and/or (ii) weaker than now, the meteorological equator should under this proposition have been nearer the true equator than is now the case. The work of other investigators has suggested that the equatorial low‐pressure belt should also be wider at times when the circumpolar westerlies weaken in either hemisphere. The changes here postulated appear to fit in with what is known of conditions around, and since, the culminating phase of the ‘Little Ice Age’ in the northern hemisphere about a century and a half ago.
The diabatic wind profile
Authors: Panofsky H. A. , Blackadar A. K. , McVehil G. E. 
Published: February 2007

AbstractWind profiles observed at various locations are compared with wind profiles predicted by Ellison on the basis of similarity theory. It is shown that theory and observations agree well for near‐neutral and unstable air; however, in stable air, factors not considered in the similarity theory may become important.The range of usefulness of the log‐linear wind profile is shown to be small.
Some experiments in the objective analysis of contour charts
Authors: Corby G. A. 
Published: February 2007

AbstractThe quality of a series of objective analyses of synoptic charts has been examined and it has been found that statistically the discrepancies from manual analyses are of the same order as the variations which arise amongst conventional analyses by different individuals. A systematic fault in the computed analyses of surface maps (viz. an underestimation of the depth of intense depressions over the ocean) was found to be due to the use of the geostrophic approximation and to other limitations of the interpolation system. Modifications designed to overcome this shortcoming have raised the standard of the analysis of depressions to that of the analyses as a whole.
Observations on the Aitken nuclei in Atlantic air
Authors: O'Connor T. C. , Sharkey W. P. , Flanagan V. P. 
Published: February 2007

AbstractThe concentration, size and distribution of charges on Aitken nuclei in air from the Atlantic Ocean were measured at a station on the western coast of Ireland where man‐made pollution was most unlikely. The results are examined in relation to the meteorological elements and human activities. Some sources of the nuclei observed in maritime air are discussed.
Heat‐balance measurements from an earth satellite ‐ an analysis of some possibilities
Authors: Bignell K. J. 
Published: February 2007

AbstractA detailed discussion of the basic ‘black’ and ‘white’ sphere experiment designed by Suomi, and successfully launched in more elaborate form in Explorer VII in October 1959, is presented. It is concluded that this experiment is in almost every respect well suited for making heat‐balance measurements from a simple unstabilized satellite, but that it suffers from the serious disadvantage of any such system that the sampling rate is inadequate for giving the daily or short‐term heat balance of any region of the earth. Other main conclusions are: the magnitude of the possible error incurred by employing a spherical detector to measure the vertical intensity of a diffuse, anisotropic radiation stream is estimated to be a few per cent only; corrections for heat transfer by conduction and radiation to the spheres from the main body of the satellite can be reduced to negligible proportions, but heating due to high velocity impacts with gas molecules may be considerable for low orbits (0.16 cal cm−2 min−1 at 200 km); the time constant of the detector is shown to be not less than about two minutes; the sensitivity is of the order of 1°K per 0·01 cal cm−2 min−1; the prospects of checking the calibration of the equipment in flight seem reasonable.
The density and structure of ice formed by accretion
Authors: Macklin W. C. 
Published: February 2007

AbstractStudies have been made of ice formed by accretion over a wide range of controlled conditions to ascertain the influence of the wind speed, ambient temperature, droplet diameter and liquid‐water concentration in the supercooled cloud, and the size of the accreting object. The density of the deposits ranged from 0·1 to 0·9 g cm−3, the density increasing with increases in the first four of the above parameters but decreasing with increasing object size. It was found that the density could be expressed as a function of − rv0/Ts, r being the median volume radius of the droplets comprising the cloud, v0 the speed with which the droplets struck the object and Ts the mean temperature of the accreting surface (in °C). The quantity rv0 is interpreted as being a measure of the force with which the droplets were packed together and Ts the temperature which governed their freezing rate. A microscopic examination of the deposits showed that at low values of − rv0/Ts (corresponding to low densities) the droplets tended to freeze together as spheres while at higher values they were distorted and spread considerably before freezing.
Model experiments relating to thermals with increasing buoyancy
Authors: Turner J. S. 
Published: February 2007

AbstractIt is pointed out that previous laboratory experiments which have been used to obtain information about atmospheric thermals have not dealt with the important case of an element whose total buoyancy is increasing. A new technique (based on the chemical release of small gas bubbles) is described here, which allows one to simulate in a liquid the increase of buoyancy due to the release of latent heat in clouds. It has been found possible to achieve experimentally two simple kinds of motion, namely, constant velocity or constant upward acceleration. These elements spread linearly with height in agreement with the predictions of a dimensional theory, at nearly the same angle as thermals in neutral surroundings.
Recent changes of east‐coast rainfall regimes
Authors: Kraus E. B. 
Published: February 2007

AbstractNew data are given which extend from 1941 to 1960 an earlier study (Kraus 1955). The analysis suggests a return to wetter conditions in low‐latitude east‐coast regions, after a drier period which persisted through nearly half a century. This change appears to be paralleled by the recurrence of lower mean temperatures in higher latitudes.
Secondary instability in steady gravity waves
Authors: Scorer R. S. , Wilson S. D. R. 
Published: February 2007

AbstractA stratified stream may be stable when flowing horizontally and yet develop a Görtler type of instability in gravity waves when the flow is curved. The equation for the generation of secondary vorticity (rotation round the streamlines) may be used to study this, and we show that the curved flow in two‐dimensional gravity waves could become unstable in real cases. This is, therefore, one possible mechanism for the generation of ‘clear‐air turbulence’ in mountain waves.
Change of terrain roughness and the wind profile
Authors: Panofsky H. A. , Townsend A. A. 
Published: February 2007

AbstractTo describe the distribution of wind with height in hydrostatically‐neutral air following a change in terrain roughness, a theory is constructed by assuming that only the air below an internal boundary is affected by the change and that air above the boundary is moving with the speed and Reynolds stress that it had upwind of the change of roughness. Unlike in the closely related theory of Elliott, the assumed velocity distribution in the lower layer is consistent, not with stress independent of height, but with continuous variation of stress from the surface to the boundary where the stress is that in the original layer. the condition of overall conservation of momentum then leads to relations between surface stress, boundary height and fetch. the theory is compared with observations at a variety of locations, and the agreement with measurements is satisfactory. In particular, a fairly sharp boundary separates the masses of air influenced by the two types of terrain; for micrometeorological distances, the slope of this interface is of order 1/10.
Fall speeds of precipitation elements
Authors: Cornford S. G. 
Published: February 2007

AbstractA basis is presented for the calculation of the terminal velocities, V, of thirteen types of precipitation element over a wide range of size and air density, ρ. It is found that changes in drag coefficient allowed for in the calculations are unimportant and that for the purpose of deducing rainfall rates from aircraft observations of precipitation particles they may be ignored; thus for particles of a given size and type.
The influence of friction on the growth and structure of baroclinic waves
Authors: Haltiner G. J. , Caverly D. E. 
Published: February 2007

AbstractAnalysis of a simple two‐level linearized baroclinic model shows that the effects of surface friction are quite significant with respect to the growth characteristics of harmonic waves. As expected, friction generally tends to reduce the amplification; however, some waves on the fringes of the unstable band which would otherwise be stable may amplify with friction. Increasing the drag coefficient has a similar effect on amplification as decreasing the thermal wind. A wave solution, comprised of two stable components travelling at different speeds, may amplify temporarily due to the resulting interference pattern which exhibits a periodic amplitude and propagation speed.The phase difference between the thermal and pressure waves is also markedly affected by the friction; for example, for the drag coefficients used, the limiting phase difference may differ by as much as 40° from the frictionless case.
Baroclinic instability and the short wavelength cut‐off in terms of potential vorticity
Authors: Bretherton F. P. 
Published: February 2007

AbstractThe stability is discussed of an infinitesimal quasi‐geostrophic perturbation to a baroclinic zonal wind which is independent of latitude, in terms of a two‐layer inviscid model with parallel but sloping upper and lower boundaries, so that the northwards gradient of potential vorticity in each layer is equal and opposite, but not a simple multiple of the difference between the basic eastward velocities. A long wavelength cut‐off to the instability is possible, as well as a short wavelength cut‐off. The mechanism for the instability is described qualitatively in terms of the balance between east‐west advection of perturbation potential vorticity, and generation by north‐south motions in the basic gradient, and the reasons for both cut‐offs are clarified. The short wavelength stable modes are described as advected Rossby waves in either the upper or the lower layer.This qualitative description is then extended to apply to the short wavelength cut‐off found by Eady, and to the short wavelength Eady modes, which are always de‐stabilized by a small gradient of potential vorticity in the interior of the fluid, together with the action of a critical layer.
A spectral model for Cisk‐barotropic energy sources for tropical waves
Authors: Padro J. 
Published: February 2007

AbstractA non‐linear, three‐dimensional spectral model on a β‐plane is developed to study the relative rǒles of important energy sources for tropical waves. Both the north‐south shear of the zonal wind and Cisk (conditional instability of the second kind) are included. Energy exchanges and wave growth rates are studied in the presence of various specified vertical profiles of latent heat. Radiation is parameterized by Newtonian cooling; it plays a minor rǒle. Latent heat is parameterized in terms of large‐scale boundary layer flow. Dissipation is also included.The model includes three layers in the troposphere and one in the stratosphere. The top of the boundary layer is taken at 900 mb and its effect is described by frictionally induced vertical velocity and surface dissipation. The initial state is an idealized form of observations taken in the Marshall Islands.Important results show that when latent heat release decreases with height and is large at low tropospheric levels, the eddies are initially generated and maintained barotropically and then Cisk assumes a dominating rǒle. When heat release increases with height, Cisk dominates at all stages of the wave development; the barotropic mechanism, however, is still necessary.It is also found that when latent heat release is maximum at the low levels, the most dominant wave is 3,000 km with an initial growth rate of 3 days in e‐folding time. The longer waves assume greater dominance at the upper levels, especially when latent heat increases with height.
Scattering in liquid haze ‐ analytic approximations
Authors: Kuriyan J. G. , Sekera Z. 
Published: February 2007

AbstractAn analytic formula is derived which describes approximately the scattering of electromagnetic waves in a haze. This formula is compared, and found to agree well, with the exact results from Mie Theory that is available in the literature. The formula is used to arrive at a simple, non‐redundant but complete parameterization of the aerosol model.
On Penman's equation for estimating regional evaporation
Authors: Thom A. S. , Oliver H. R. 
Published: February 2007

AbstractThe form of Penman's evaporation equation most extensively applied in hydrometeorology is discussed. It is shown that this equation underemphasizes the importance of ventilation relative to radiation in maintaining regional evaporation. A generalized ventilation term is proposed and a modified equation for evaporation derived. This new equation is calibrated to give the same annual total for short vegetation as Penman's original version. It predicts both an enhancement of winter evaporation at the expense of summer evaporation and a significant increase in annual total evaporation with vegetation size, especially in regions of frequent substantial rainfall.
Coastally trapped waves in the atmosphere
Authors: Gill A. E. 
Published: February 2007

AbstractIt is suggested that the ‘coastal lows’ observed off southern Africa are similar in structure to ‘coastally trapped waves’ in the ocean. Inversion conditions typical of the area prevent escape of energy upwards and Coriolis effects keep energy trapped against the high escarpment which borders the continent. Coastal disturbances are produced because low‐level flow in the synoptic‐scale systems cannot cross the barrier provided by the escarpment. Nonlinear effects cause lows to be more prominent than highs. A simple nonlinear forced Kelvin wave model is found to reproduce many of the features observed.
Squall lines observed in GATE
Authors: Mansfield D. A. 
Published: February 2007

AbstractA study of convection as portrayed by Oceanographer radar during phase III of GATE reveals four occasions on which an organized line of convection moved with a speed close to or greater than the wind speed at any level. They are shown to resemble closely the analytical model and numerical simulation of tropical line squalls developed by Moncrieff and Miller. This form of organization is associated with a lowlevel wind maximum in the direction of movement.
Probing tornadoes with a pulse doppler radar
Authors: Zrnic D. S. , Doviak R. J. , Burgess D. W. , Brown Rodger A. 
Published: February 2007

AbstractMaximum tornado wind speeds and their radii are deduced by least square fitting of the vortex model velocity spectra to those measured with a pulse Doppler radar. Spectra are analysed from the Stillwater, Oklahoma, 13 June 1975, tornado. Simulated spectra are fitted to those measured for pulse volume gates nearest the vortex, and thus a tornado's position relative to those gates is estimated. Estimated maximum tangential velocity is 92ms−1 at an altitude of 630m and 85ms−1 at 1.5km; tornado diameter is 300m. the observed spectra have an asymmetry that suggests targets that are centrifuged outwards, with a velocity of 13ms−1. One spectrum analysed from the Union City, Oklahoma, 24 May 1974, tornado shows a bimodal shape similar to Stillwater spectra. Deduced maximum velocity is 72ms−1 and diameter 200 m.
Weakly nonlinear stability theory of stratified shear flows
Authors: Maslowe S. A. , Drazin P. G. 
Published: February 2007

AbstractA derivation is given of the first‐order, nonlinear amplitude equation governing the temporal evolution of finite‐amplitude waves in stratified shear flows. the theory has been developed on an essentially inviscid basis by perturbing away from the linear neutral stability curve in Richardson number‐wavenumber space. However, viscosity and heat conduction are still required in order to eliminate the singularities that occur in the inviscid limit. Holmboe's mixing layer model has been studied by applying the present theory and the results show, surprisingly, that subcritical instability can occur, i.e. modes that would be stable on a linear basis (e.g. when the Richardson number is greater than 1/4) become unstable when the initial perturbation amplitude is greater than some critical value. an instability due to resonance which occurs at a Richardson number of 0·22 is also revealed by the analysis. These results have interesting implications in connection with clear air turbulence which are discussed herein.
Observation of inertial waves in the stratosphere
Authors: Thompson R. O. R. Y. 
Published: February 2007

AbstractA series of radiosonde flights over Laverton, Victoria (38°S), is found to have sufficient vertical (100m) and temporal (3 h) resolution, and sufficient length (28 days) to detect inertial waves. Fourier analysis shows that in the stratosphere there is a strong anticyclonic rotation of the wind vector which has energy concentrated near the local inertial frequency. This rotation is associated with a vertical wavelength between 1 and 3 km, and a downward phase propagation. There is no sign of inertial waves in the troposphere. The waves appear to be generated below the stratosphere and spread upwards.
The turbulence kinetic energy budget in convective conditions
Authors: Caughey S. J. , Wyngaard J. C. 
Published: February 2007

AbstractData from the 1973 Minnesota atmospheric boundary layer experiment are used to investigate details of the turbulence kinetic energy budget in convective conditions. Surface layer results are presented in nondimensional form and compared with conclusions from earlier Kansas data. Above the surface layer the terms are nondimensionalized using mixed layer similarity length and velocity scales and compared with indications from other recent experiments.
Rainfall along the east coast of southern Africa, the southern oscillation, and the latitude of the subtropical high pressure belt
Authors: Dyer T. G. J. 
Published: February 2007

AbstractEighteen rainfall series within a latitude belt 28°08′S to 30°25′S are inspected for relationships with Pittock's L index for the latitude of the subtropical high pressure belt (eastern Australia), and the southern oscillation index. Principal components analysis is used to reduce the dimensions of each of the three data sets, and the components for the pressure systems are used as independent variables in a step‐wise regression analysis; rainfall components are taken as the dependent variables. Useful relationships exist between rainfall and Pittock's L, but there is no evidence to suggest that the same situation applies for the southern oscillation index. The results agree with those recently obtained for Mauritius by M. D. Dennett.
Mid‐ocean observations of atmospheric radiation
Authors: Simpson James J. , Paulson Clayton A. 
Published: February 2007

AbstractMid‐ocean (35°N 155°W) observations of the various components of radiative flux were made from the R/P FLIP during the period 2 through 13 February 1974. Cloud cover ranged from clear skies to overcast, and water vapour pressure varied between 9 and 18 mb, with sea surface temperature near 15.0°C.The net longwave radiative fluxes reported here were obtained: (1) by taking the difference between simultaneous measurements of net all‐wave and net solar fluxes; and (2) by direct measurements with a net longwave radiometer designed by G. W. Paltridge. When observations during rain and fog are excluded, the difference between night‐time 15‐minute averages by the two methods is generally less than lmWcm−2. During day‐time, indirect measurements are often larger than direct by about 5mWcm−2; from internal evidence we prefer the direct values.The albedo of the sea surface was calculated from simultaneous measurements of downward and upward solar fluxes. The observations were analysed to represent albedo as a function of solar altitude and atmospheric transmittance, following the work of R. E. Payne; our results suggest that Payne's smoothed representation is suitable for use over the open ocean. Albedo was observed to decrease with increasing wind speed for clear skies with solar altitude between 15 and 30 degrees but no variation was discernible at higher solar altitudes.Empirical formulae for calculating both shortwave and net longwave components of the radiative flux were compared with measurements. A formula due to F. E. Lumb for determining the incident solar flux given solar altitude, cloud amount and cloud type, consistently yields good agreement with the measurements, within about lmWcm−2. Daily averages of net longwave flux calculated from several empirical formulae using a linear correction for clouds are within 2mWcm−2 of the observations reported in this paper. Since daily radiation balance values were measured as only 5mWcm−2, the limitations of the best current empirical formulae are evident.
An experimental forecast using a non‐hydrostatic mesoscale model
Authors: Carpenter K. M. 
Published: February 2007

AbstractA non‐hydrostatic mesoscale model formulated by Tapp and White has been extended to include the effects of orography and the variation of the large‐scale meteorological situation. Other changes to the model, particularly in the parametrization of boundary layer turbulence, are described and its application as a forecasting tool is illustrated by an extensive study of one situation.