bluuebunny/crossref_metadata_2025_split huggingface dataset:
Generalized treatment of particulate scattering in Dobson ozone spectrophotometer calculations
Authors: Gardiner B. G. 
Published: February 2007

AbstractIn the calculation of atmospheric total ozone from ultraviolet spectrometry, the particulate scattering term is usually regarded as a linear function of wavelength. A method due to R. E. Basher, in which it is treated as a quadratic polynomial, is here generalized to include a polynomial of any degree, and the quadratic approximation is seen to be somewhat arbitrary.It is shown that the determination of the quadratic and higher coefficients from Dobson spectrophotometer observations is limited by systematic errors of measurement, and that these errors are doubled or trebled by attempting to correct even for the quadratic coefficient. It is concluded that Basher's method of calculation is at present inadvisable.
An assessment of the Keily probe for the ground‐based measurement of drop size distributions in clouds
Authors: Corbin R. C. , Latham J. , Mill C. S. , Stromberg I. M. 
Published: February 2007

AbstractA series of experiments has been performed to calibrate and assess the reliability of the Keily probe for ground‐based measurements of droplet size distributions in cloud. Tests were conducted in natural and artificially produced water clouds at our field research station on Great Dun Fell, and in a specially constructed cloud tunnel. Comparisons were made with drop size distributions measured with a Knollenberg ASSP device and with MgO coated slides. Collection efficiencies were obtained for the Keily probe for various values of ventilation speed and orifice size. It was concluded that the instrument operated consistently and reliably within the range of conditions applicable to our ground‐based field research.
Differences between morning and evening temperatures of cloud tops over tropical continents and oceans
Authors: Riehl Herbert , Miller Alan H. 
Published: February 2007

AbstractLongwave radiation measurements made in the water vapour window by the satellite NOAA‐2 are examined for the period 15 June to 30 September 1974, in two oceanic and two continental tropical areas. Satellite overpasses are near 09 and 21 local time. It is found that convective cloud tops over land are much colder (and higher) in the evening than in the morning. The reverse is true over sea; further, the absolute frequency of very cold clouds is less there than over land. A specific cloud mass which could be followed for one week shows a morning‐evening variation in cloud top temperature in agreement with statistical deductions.
A temperature correction for Tucker's ocean rainfall estimates
Authors: Dorman Clive E. , Bourke Robert H. 
Published: February 2007

AbstractA method suggested by G. B. Tucker of estimating rainfall from present weather observations is tested on 28 coastal stations. Tucker's method was developed from a group of stations in Great Britain; at other latitudes, due to air temperature differences, the Tucker estimates may be several times too high or too low. Regression formulae are presented to adjust yearly, quarterly, and monthly mean precipitation values for air temperature. Corrected rainfall maps based upon ocean weather station data reveal a formerly undetected rainfall maximum in western mid‐latitudes of the North Pacific and North Atlantic Oceans.
Effects of aerosol optical properties and size distributions on heating rates induced by stratospheric aerosols
Authors: Mugnai A. , Fiocco G. , Grams G. 
Published: February 2007

AbstractA previous analysis of the energy balance of small particles in the earth's atmosphere is extended to substances that have special significance in the stratospheric aerosol layer, such as sulphuric acid and volcanic ash. The analysis is based on establishing a balance between the power absorbed by the particles from solar and planetary radiation fields, the power emitted by the particles as thermal radiation and the power exchanged through collisions with the ambient gas. The planetary radiation field is calculated as a function of altitude and includes radiation from the surface as well as emission and absorption by the infrared bands of carbon dioxide, ozone and water vapour. The various terms in the energy balance equation change as a function of the composition, radius and altitude of the aerosol particles, and of the latitude, season, time of day and albedo of the underlying earth‐atmosphere system; aerosols may heat or cool the atmosphere and their temperature may differ from the ambient gas temperature. Average values for rates of heating induced in the ambient gas by monodisperse and polydisperse aerosol particles are computed for various substances. The rates of heating induced by volcanic ash particles and sulphuric acid droplets are calculated for equatorial, mid‐latitude summer and mid‐latitude winter conditions for altitudes to 40 km.Our results illustrate the effects on atmospheric heating rates of changing the size distribution of the particles and the particle composition. We also show that heating rates of at least 0.25 K day−1 were induced by the stratospheric aerosol layer after the 1963 eruption of the Gunung Agung volcano in Bali.
A parameterization of heat convection for a numerical sea breeze model
Authors: Dalu G. A. 
Published: February 2007

AbstractA hydrostatic model of a sea breeze circulation is developed through numerical integration of the primitive equations. Air flow is assumed inviscid and external gravity waves are filtered by using a rigid‐top boundary condition. Heat is fed directly into the model, and a parameterization of its distribution is developed which does not use diffusion coefficients explicitly. The model is stable for an integration timestep of up to 14 minutes. Computations are carried out for the latitude of Rome. The Apennines are parameterized as a vertical rigid wall, parallel to the shore.The results show good agreement with wind profiles given by pilot balloon soundings at Rome Airport in conditions of a sea breeze circulation. A comparison is made with the two‐dimensional model of Neumann and Marher.
Resonance characteristics of linear lee waves in an atmosphere of three layers
Authors: Berkshire F. H. , Pickersgill A. O. 
Published: February 2007

AbstractThe upward leakage of wave energy from a two‐layer troposphere into the stratosphere is examined; the changes produced in the natural complex modes of the system by altering the parameters are found to give rise to some quasi‐resonance phenomena. Under special circumstances there may exist modes which decay extremely rapidly downstream and these provide a qualitative explanation for some features of observed flows.
Low‐level air flow circulation over the Arabian Sea during the summer monsoon as deduced from satellite‐tracked superpressure balloons. Part II‐Analysis of the flow field
Authors: Cadet Daniel , Olory‐Togbé Paul 
Published: February 2007

AbstractTrajectories of superpressure balloon flights in the tropical boundary layer over the Indian Ocean during the 1975 summer monsoon are analysed in relation to conventional meteorological observations, mainly ship reports. An assimilation of these randomly distributed observations is performed to compute mean gridded fields of wind and pressure during four periods defined according to monsoon activity over the Indian sub‐continent. Mean cloud cover fields over a 2.5° × 2.5° square are also determined from satellite images. The main features of the low‐level monsoon circulation are deduced from the two sets of data; these are in conflict with earlier conclusions deduced from the interpretation of local conditions. The differences in meteorological fields between the various phases of the activity of the monsoon over India are studied and discussed.
A study of the major stratospheric warming of 1976/77
Authors: O'neill A. , Taylor B. F. 
Published: February 2007

AbstractThe unusual atmospheric behaviour observed at middle and high latitudes during the winter of 1976/77 is discussed in both synoptic and dynamical terms, using routine, objectively analysed data. During this period the growth of large amplitude, planetary‐scale waves in the troposphere resulted in a marked wave growth in the stratosphere. A qualitative discussion of the interaction between these waves and the zonal flow is followed by referring to the temporal evolution of the relevant terms in the zonally averaged momentum and heat equations. It is shown that the export of momentum from high latitudes by the waves was crucial in effecting a zonal wind reversal in both troposphere and stratosphere. The importance of this mechanism during the period of study indicates the need for a revision of the currently favoured dynamical model of the stratospheric sudden warming.
The observed zonal wind cycle in the southern hemisphere stratosphere
Authors: Tucker G. B. 
Published: February 2007

AbstractZonal winds in the stratosphere for a period of 20 years have been analysed at nine stations between 7°S and 66°S centred on the longitude of eastern Australia. The amplitude, period and phase of the third (‘quasi‐biennial’) cycle are determined. Although a coherent pattern emerges in the variation of period with latitude and height it is concluded that, at least in the tropics, the representative period is 832 days (27.35 months). The well‐known maximum in amplitude of this third cycle in the tropics decreases to a minimum at about 30°S but increases again polewards, reaching a maximum at about 50°S at the highest levels of observation (6mb). The phase of the cycle ‘leads’ at high levels and low latitudes and also at the height and latitude of the polar night jet. Below these maxima there is a downward propagation of the cycle but little phase variation with height exists in middle latitudes. For the tropics, the variation with latitude of amplitude and phase is consistent with lateral diffusion of a forced equatorial cycle, with eddy diffusion coefficients of 1 × 109cm2s−1 at 80mb, decreasing to 3 × 108cm2s−1 at 25mb.
Mesoscale structure of line convection at surface cold fronts
Authors: James P. K. , Browning K. A. 
Published: February 2007

AbstractIn this paper we consider 15 cases of line convection at ana‐cold fronts which have been observed by radar. Although line convection can be a simple two‐dimensional feature, it is usually broken up into line elements having lengths from a few to many tens of kilometres separated by somewhat smaller gaps. The passage of a line element is accompanied by a short burst of heavy precipitation, a temperature drop of about 2degC, a sudden veer and decrease in wind speed, and a pressure jump of 1 to 2 mb. If a gap between line elements passes over a station, however, the changes can occur gradually over a period of up to an hour. Despite the variable size of the line elements, they are found to share common characteristics. They are always oriented slightly clockwise with respect to the synoptic cold front. They all move with the same velocity as their neighbours on a given front, with a component parallel to the front in the direction of the strong low‐level flow which occurs ahead of the front. Moreover, the line elements tend to travel in a fairly predictable manner, largely unaffected by topography and with the major features having lifetimes of several hours.
Interpretation of Nimbus 5 SCR data for obtaining vertical temperature profiles
Authors: Molnár Gy. 
Published: February 2007

AbstractIn this paper a statistical estimator is used to retrieve vertical temperature profiles above an area for which autocorrelation matrices of the temperature profile have been computed for each season using radiosonde data. The temperature dependence of atmospheric transmittance has been taken into account. We find that in cloudless cases the retrieved vertical temperature profiles have an average r.m.s. error of 2–3.5 K, when compared with appropriate radiosonde measurements. We note that to achieve this rather satisfactory result it is not necessary to divide the atmosphere into more than 18 levels; and we will show that it is advantageous to use the total covariance matrices instead of only the diagonal elements. To obtain further comparisons between retrieved and radiosonde profiles, the analysed gridded radiance values have been used, and in this case the r.m.s. error is 2.5–3.8 K.
A high resolution infrared radiative transfer scheme to study the interaction of radiation with cloud
Authors: Roach W. T. , Slingo A. 
Published: February 2007

AbstractThis paper describes a high resolution radiative transfer scheme which calculates infrared fluxes and heating rates in a cloudy atmosphere. It is intended as a research tool for use in studies of the role of radiation in the physics of fog and layer cloud. The spectrum is split into five bands and allowance is made for molecular absorption by the water vapour 6.3 μm band and the rotation band beyond 20 μm, the 15 μm carbon dioxide band, the 9.6 μm ozone band, and the continuum absorption by water vapour in the 10 μm atmospheric window. The strong absorption by cloud water droplets is calculated directly from the droplet size distribution function. The scheme has been run with a model stratocumulus cloud included, using data based on tethered balloon observations at Cardington. A large cooling rate of 8.7 K per hour is shown to exist at the cloud top.
Recent variations in annual‐mean maximum temperatures over Australia
Authors: Coughlan M. J. 
Published: February 2007

AbstractA data set of annual‐mean maximum temperature variations over the Australian continent, including Tasmania, for the period 1946 to 1975 has been prepared, using all available data. From this data set, trends over the 30‐year period indicate a space scale of variability typically less than 1500km. Most of Australia has experienced a rise in annual‐mean maximum temperature over the period although the proportion which has experienced a fall is not insignificant. This has implications for the determination of hemispheric trends in temperature south of the equator.Comparisons between annual‐mean maximum temperature anomalies and annual rainfall are made, which show that there is no strong overall relationship. Typically negative correlations do emerge, however, when comparisons are made between temperature variations and the two major patterns of rainfall derived from a principal component analysis. It is further demonstrated that the pattern of trends in temperature can be related to a large extent to the trends in circulation features to which these two major patterns have been ascribed: the Southern Oscillation, and the mean latitude of the high pressure belt over eastern Australia.
The cellular structure of narrow cold‐frontal rainbands
Authors: Hobbs Peter V. , Biswas Kumud R. 
Published: February 2007

AbstractThe heaviest precipitation in narrow rainbands situated along surface cold fronts has been observed on radar PPI displays to be organized into regularly spaced small mesoscale elements having shapes which are roughly elliptical. The long axes of the ellipses are essentially parallel to each other and oriented at an angle of about 35° to the front.
Aircraft observations of the structure of the lower boundary layer over the sea
Authors: Nicholls S. , Readings C. J. 
Published: February 2007

AbstractResults from an investigation of the turbulence structure of the lower half of the convective boundary layer over the sea around the UK in a wide variety of meteorological conditions are presented. The data were obtained on eight flights made by the Hercules aircraft of the Meteorological Research Flight.Differences in structure between boundary layers over sea and over land are emphasized, the most notable being the relatively increased importance of mechanically driven mixing over the sea. This means that a more general scaling scheme is required which retains both u* and zi as scaling parameters. Such a scheme orders the results quite effectively. Dimensionless profiles of momentum, sensible heat and latent heat fluxes are presented, together with dimensionless variance profiles. Excellent agreement is found between these and theoretical predictions from numerical models. Surface fluxes are estimated and compared with bulk aerodynamic formulae.The turbulence statistics are shown to be in good agreement with those published by other workers.
A diagnostic study of the long‐term budget of momentum of atmospheric large scale motion over the British Isles
Authors: Holopainen E. O. 
Published: February 2007

AbstractDifferent terms in the equations of zonal and meridional motion for large scale flow in the atmosphere have been evaluated using British aerological data for the period 1974‐76; the effect of motion on scales smaller than a few hundred kilometres on large scale flow is evaluated as the residual term in these equations.In the long‐term mean there is horizontal advection of zonal momentum into the area of the British Isles. This advection, which is characteristic of both the time‐mean flow and transient disturbances and takes place mainly in the zonal plane, is to a large extent compensated for by Ferrel‐type ageostrophic meridional circulation. The momentum budget in the meridional direction reflects the high degree of geostrophic balance in the time‐mean zonal flow in the free atmosphere.The mean residual forces in the atmosphere below 700mb are used to infer the vertical sub‐grid scale flux of momentum by assuming that the residual forces at these levels are due to vertical eddy stresses (i.e. stresses involving the vertical velocity component) only, and by evaluating the stress at the earth's surface with the aid of the geostrophic drag law. The results indicate that the annual mean vertical flux of zonal momentum above about 900mb is downwards but relatively small; the corresponding flux of meridional momentum is relatively large and upwards. Mesoscale circulations in connection with fronts are suggested as a possible explanation of the latter phenomenon which, however, may also partly arise in calculations as the result of the poor vertical resolution of the routine upper wind observations in the atmospheric boundary layer.The residual force in the upper troposphere is very variable. However, consistent with an earlier analysis of the kinetic energy budget using the same data, it exhibits the ‘negative viscosity’ phenomenon, implying acceleration of the large scale flow by motion on scales smaller than the average distance between aerological stations.
Zonal and meridional variations of eddy fluxes induced by long planetary waves
Authors: Frederiksen J. S. 
Published: February 2007

AbstractA study is made of the horizontal variations of eddy momentum and heat fluxes induced by long planetary waves in a linear two‐layer quasi‐geostrophic spherical model. A wide range of basic flows, consisting of upper‐layer, pure baroclinic or pure barotropic long waves together with solid‐body rotation or either of two zonal jet profiles, characteristic of the troposphere, are considered. The superposition of long planetary waves on otherwise zonal flow profiles has an effect on the eddy fluxes which is profound but is highly variable, depending on the basic flow. It is found, however, that for all profiles involving basic upper‐layer or baroclinic waves, the horizontal structure of both momentum and heat fluxes may be understood in terms of a generalization of Phillips's criterion for incipient instability. For these profiles, the regions of preferential development of baroclinic eddies are also found to be related to the general stability criterion. When barotropic planetary waves are present in the basic flows, the structure of the eddy fluxes is more complicated, reflecting the strong zonal wavenumber coupling in the disturbance streamfunctions.
The estimation of rain from satellite‐borne microwave radiometers
Authors: Lovejoy S. , Austin G. L. 
Published: February 2007

AbstractRecent advances in satellite‐borne microwave radiometry have led to interest in their use for rainfall amount estimation. The potential accuracy of such techniques is investigated in detail, and is estimated to be about ±70% for rainfall rate estimates, even when many wavelengths are used. The effects of the low spatial and temporal resolution of the most recently launched microwave radiometer (on Nimbus 7) are also investigated, using radar‐based computer simulations. The effects are shown to produce r.m.s. errors of ±200, ±310% respectively, yielding a total error of ±370% for independent processes.
Eddy‐fluxes and spectra in the GATE sub‐cloud layer
Authors: Thompson N. , Webber K. L. , Norris B. P. 
Published: February 2007

AbstractAn investigation of the structure of the GATE sub‐cloud layer carried out using turbulence sensors attached to a tethered balloon cable is described. The observations were made at one or two levels up to 400m near the centre of the C‐scale ship array during the final phase of the experiment. The data were used to derive the vertical eddy fluxes of momentum, sensible and latent heat and the spectra and cospectra of the turbulence parameters, all over one‐hour long periods. Surface fluxes were estimated using the bulk aerodynamic formulae.The results were classified according to the convective activity prevailing during each one‐hour period. Marked changes in the vertical flux profiles with increasing convective activity are demonstrated. Spectra and cospectra in conditions of suppressed convection (small cumulus clouds only, no showers) show the increasing importance of larger scale mixing processes as heights increase to about 300m, but above this (near the top of the mixed layer) processes on a smaller scale are found to predominate. On these latter scales there is an upward flux of momentum which is a consequence of rather shallow vertical mixing in a region where wind speed decreases with height: in more disturbed conditions deeper convection, coupled with the reversed vertical gradient of wind, causes an upward momentum transfer on larger scales.
Mass divergence in tropical weather systems Paper I: Diurnal variation
Authors: McBride John L. , Gray William M. 
Published: February 2007

AbstractThe diurnal variation of mass divergence and vertical velocity is documented for tropical summertime oceanic weather systems in the Western Pacific, Western Atlantic and the GATE region. It is shown that it is large and has the same basic character in all regions.Gray and Jacobson (1977) proposed that the diurnal variation of mass convergence is a result of diurnal differences in the net radiative and convective heating rates in the thick cirrus‐shield covered weather systems and their surrounding clear areas. Fingerhut (1978) has developed a numerical model which appears to substantiate this hypothesis. A comparison of observations with results from his model reveals that a simple radiation‐condensation model simulates most of the observed diurnal variations of convergence. The hypothesis is that radiational forcing is one of the major contributors to the maintenance and modulation of tropical weather systems.
Energetics of diabatic mesoscale circulation: A numerical study
Authors: Dalu G. A. , Green J. S. A. 
Published: February 2007

AbstractMesoscale circulations, induced by mesoscale available potential energy diabatically generated in the boundary layer are studied through the numerical integration of primitive equations. The energetics of a sea‐breeze simulation is studied in some detail. After 12 hours of simulation the kinetic energy is about a quarter of the mesoscale available potential energy diabatically produced. We comment on the energy lost by the upstream difference scheme, and on some aspects of the unavailability of available potential energy in such a system that together describe this level of inefficiency.