bluuebunny/crossref_metadata_2025_split huggingface dataset:
Recent developments in long‐range forecasting in the Meteorological Office
Authors: Murray R. 
Published: February 2007

AbstractSix years ago at the end of November we issued the first monthly forecast to the British public. At that time the forecasts were based on an Analogue Selection procedure and a so‐called Physical Discussion. In principle these two inter‐related approaches still form the basis of the present operational method, but considerable changes have taken place and these are reflected in a modest improvement in the accuracy of the monthly forecasts.This overall improvement arises from three main sources. In the first place, we have steadily extended and improved our store of readily available, processed data. Many people have of course been responsible for the essential data‐processing side of our work, which is still continuing, but I must mention J. M. Craddock and M. H. Freeman for laying good foundations in the early days. In the second place, we have carried out numerous synoptic and empirical studies. All of these have given useful background information and some understanding of the nature of large‐scale circulation and weather anomalies. Many of our investigations have been aimed at providing statistically based aids for the prediction of UK weather. We have increased the scope and range of our studies which are not confined to the monthly time scale. In particular a good deal of work has been done on the seasonal time‐scale, and in the past year or two we have carried out experimental forecasts, originally for winter and summer but now for every season. In the third place we have gained a lot of experience of the particular problems as a result of both research and operational forecasting. I would like to touch upon a few points in elaboration of these remarks.
Reflection coefficient of natural vegetation, crops and urban surfaces in Nigeria
Authors: Oguntoyinbo J. S. 
Published: February 2007

AbstractReflection coefficients measured over a wide variety of natural and agricultural vegetation surfaces in Nigeria (lat. 4° 40′ to 13° 30′N) were between 0.057 to 0.251; and were inversely related to the vegetation height. Considerable seasonal differences were found with unexpected low values of reflectivity during the harmattan haze in the dry season. Possible reasons for these seasonal differences are discussed. The weighted mean annual reflection coefficient for Nigeria was calculated to be 0.178. This value was consistent with the relationship between surface reflection coefficient and latitude found from similar results from six other locations in the Northern Hemisphere. Urban coefficients were found to be lower than those for rural settlements or temperate zone urban centres.
The detection of ice clouds from remote measurements of their emission in the far infra‐red
Authors: Houghton J. T. , Hunt G. E. 
Published: February 2007

AbstractIt is demonstrated that a pair of wavelengths can be chosen in the far infra‐red such that the absorbing properties of water‐vapour are the same at the two wavelengths while the scattering and absorbing properties of ice particles are different. The results of calculations show that emission from the atmosphere as observed by a satellite radiometer at the two wavelengths will be sensitive to the presence of cirrus cloud. From such measurements of emission near 50μ and 120 μ in wavelength, an indication of the thickness of the cloud can be obtained. Supporting measurements near 2.6 μ will also supply information regarding the particle size in the cloud.
Ozone profiles and ozone fluxes in the atmospheric surface layer
Authors: Galbally I. E. 
Published: February 2007

AbstractSome new measurements of the ozone flux by the profile method have been made and these are compared with others in the literature. A treatment of ozone transfer to the surface is given which takes account of the resistances offered by the fully turbulent air layers and by the surface roughness layer. It is found that the ozone flux is proportional to the ozone concentration at the Earth's surface and, for the surfaces considered, the ozone destruction coefficient has an approximate value of 1 cm s−1.
Absorption coefficients of ozone for use in the determination of atmospheric ozone
Authors: Walshaw C. D. , Dobson G. M. B. , MacGarry B. M. F. 
Published: February 2007

AbstractLaboratory measurements at low temperatures of the ozone absorption coefficient differences required in the standard spectroscopic measurement of atmospheric ozone are described. The measurements were made with a Dobson spectrophotometer and a quartz‐iodine source. The results at the standard wavelength pairs are

The effective temperature was – 42°C (± 2°C).These results are compared with those of other workers.The error in measured total ozone amount caused by changes in stratospheric temperatures is discussed. Maximum errors of about 4 per cent seem possible in spring warmings, the apparent ozone amount being too low.
Lagrangian‐Eulerian time‐scale ratios estimated from constant volume balloon flights past a tall tower
Authors: Angell J. K. , Pack D. H. , Hoegker W. H. , Delver N. 
Published: February 2007

AbstractThe ratio of Lagrangian and Eulerian time scales of motion in the planetary boundary layer is estimated from radar observations of 35 constant volume balloons (tetroons) flown past the 460 m high BREN tower at the Nevada Test Site. On the average, the peak energies of the Eulerian and tetroon vertical velocity spectra occur at periods near 6 and 18 minutes, yielding a mean Lagrangian‐Eulerian scale ratio, β, of about three, β increases with increase in wind speed, decreases with increase in r.m.s. vertical velocity, and is inversely related to vertical turbulence intensity, with β ranging from 4.5 at a turbulence intensity of 0.05 to 2.5 at turbulence intensities exceeding 0.3.
The first year of the selective chopper radiometer on Nimbus 4
Authors: Barnett J. J. , Cross M. J. , Harwood R. S. , Houghton J. T. , Morgan C. G. , Peckham G. E. , Rodgers C. D. , Smith S. D. , Williamson E. J. 
Published: February 2007

AbstractThe selective chopper radiometer, an instrument for the remote measurement of atmospheric temperature from the surface to about 50 km altitude, was launched on the Nimbus‐4 satellite in April 1970. The performance of the instrument during its first year of operation is described. Good data have been received throughout this period. Various mean atmospheric cross‐sections, temperature profiles and thickness maps are presented as examples of the data which are available from the instrument.
The measurement of mesoscale vertical motions in the atmosphere
Authors: Hardman M. E. , James D. G. , Goldsmith P. 
Published: February 2007

AbstractA technique is described for determining the three‐dimensional field of vertical air motion in the vicinity of mobile fronts. Radar reflectors are dropped from an aircraft at a height of 5 km and followed by high precision tracking radars. By making assumptions regarding the movement and conservativeness of the frontal system it has been possible to use this technique to obtain horizontal winds over a volume approximately 150 × 100 × 4 km depth with a typical drop separation of 30 km. Using the equation of continuity, vertical velocities have been calculated with an uncertainty of ± 1 ‐ 2 cm s−1. In a warm front investigated on 19 January 1969, close agreement was obtained between the rainfall observed at the surface and that computed from the vertical velocities assuming saturation of the rising air.
Coalescence in a turbulent cloud
Authors: Woods J. D. , Drake J. C. , Goldsmith P. 
Published: February 2007

AbstractThe results of two experiments show that the collision efficiency of small droplets is significantly increased when the interacting drops fall through a laminar shear flow of about 10 s−1. The structure of microturbulence in clouds is considered and it is shown that shears of this magnitude are likely to occur only within a narrow spectral band. This peak in the shear spectrum occurs at a scale that is much larger than the interaction distance of cloud droplets having radii of about 20 γm. Hence it is a good approximation to describe droplet collisions in a turbulent cloud as though they occurred in a steady laminar shear flow. It is argued that this enhanced droplet coalescence in turbulent clouds may account for the observed development of large cloud droplets (radii < 30γm) in cumulus clouds at rates greater than can be explained by condensation and the efficiency of still‐air coalescence.
The influence of tropical east Pacific Ocean temperatures on the atmosphere
Authors: Rowntree P. R. 
Published: February 2007

AbstractA version of the nine‐level hemispheric model of the atmosphere developed at the Geophysical Fluid Dynamics Laboratory has been used to test Bjerknes' hypothesis that fluctuations of ocean temperatures in the tropical east Pacific are responsible for major variations in the position and intensity of the Aleutian surface low. The results of four 30‐day integrations, two with warm and two with cool tropical east Pacific (maximum differences 3.5°C) are analysed, and verified against observational data.The ocean variations had important effects on the model atmosphere, both tropical and extra‐tropical. The warmed ocean heated the air above and induced a surface low near the sea temperature maximum; associated low‐level convergence and ascent gave increased tropical rainfall over the central and east Pacific with decreases over the west Pacific and parts of South America. The related upper flow changes generated a subtropical jet maximum with persistent troughing to the north over the mid‐latitude east Pacific. The Aleutian low was shifted east and deepened, confirming Bjerknes' hypothesis. There was strong similarity between the mid‐latitude flow over the Pacific in the warm cases despite major differences between the two cases with cool tropical east Pacific.The importance both of tropical surface conditions and of extra‐tropical influences on the model Tropics is indicated and an interaction mechanism proposed. The early development of differences between the experiments suggests that it is important to use correct tropical sea temperatures for short‐range numerical prediction in the Tropics. However, mid‐latitude effects were not significant till a week after the onset of deep tropical convection.
An investigation into meso‐scale precipitation distributions in a warm sector depression
Authors: Atkinson B. W. , Smithson P. A. 
Published: February 2007

AbstractAfter reviewing previous work on the subject, a case study is presented to illustrate and to explain the different spatial scales of rainfall distribution associated with a warm sector depression. Autographic rain gauge records for England and Wales are used to determine short period (13 min) rainfall patterns throughout the passage of the depression. From these data, large meso‐ (200 km) and small mesoscale (50 km) rain areas are distinguished in the warm front and warm sector. In the warm front, the small mesoscale rain areas are an expression of similar‐sized precipitation systems, which, as they move parallel to the surface front, trace out the large mesoscale rain areas. Mesoscale rainfall pulses are found in the warm sector, but their origin remains obscure.
Charge separation due to riming in an electric field
Authors: Aufdermaur A. N. , Johnson D. A. 
Published: February 2007

AbstractIce pellets were grown by accretion of supercooled drops, 20–100 μm diameter, at temperatures between −5 and −15°C in a small wind tunnel at an air speed of about 10 ms−1. An electric field of about 50–150 kV m−1 could be applied at the surface of the pellet. The pellet, and induction rings upstream and downstream of the pellet, were connected to electrometers and analysing circuits of sufficient sensitivity and speed to measure, correlate and display individual charging events. Charged particles entering the apparatus could be excluded from analysis by the upstream induction ring. The downstream ring was used to identify charged particles originating at the pellet. Significant charge separation occurred only in the presence of an electric field, and was consistent with charging by electrical induction. Charges between 2 and 30 fC (1 fC = 10−15 Coulomb = 3.10−6 e.s.u.), depending on drop size, were observed at a rate of about one to ten events per 1,000 accreted drops. Evidence suggesting that these charging events are the result of some drops colliding with the pellet at grazing incidence is described. This process seems adequate to account for the generation of charge in thunderclouds.
A case study of a high level Canberra flight on 11 September 1968
Authors: Axford D. N. 
Published: February 2007

AbstractA case study is presented of a high level flight by the MRF Canberra showing most of the characteristic features of intermittent clear air turbulence, gravity waves and smooth flight. Winds and temperatures obtained from two 500 km runs across a sharp upper trough are used to calculate energy spectra and cross‐spectra over a range of wavelengths from 250 m to 100 km. The spectra show clearly the important contribution of the gravity waves in the range 1 km to 10 km, and the negligible contribution of the total high frequency energy in the case of intermittent slight clear air turbulence.
Humidity and temperature microstructure near the ground
Authors: Martin H. C. 
Published: February 2007

AbstractDay‐time records of the microstructure of humidity and temperature at 2 and 4 m are analysed. Supporting data include the temperature and wind gradients, the net radiation, the sensible heat flux, and a derived value for the latent heat flux.The two variables are remarkably similar and share the following properties: The characteristic scale of turbulence increases with height and decreases with increasing instability beyond near‐neutral conditions. The logarithmic spectra follow a −5/3 slope for wave numbers greater than 0.15 m−1. In this range, the spectral estimates increase with increases in the appropriate flux (sensible or latent heat flux for temperature or humidity spectra), and decrease with height.The humidity variance contains large‐scale components which are of lesser importance in the temperature variance. This difference in the two variables has tentatively been attributed to properties of the site.
The spectral density technique for the determination of eddy fluxes
Authors: Hicks B. B. , Dyer A. J. 
Published: February 2007

AbstractThe determination of turbulent fluxes from measurements of spectral densities of velocity, temperature and humidity is discussed as a technique applicable to the open ocean. A preliminary investigation over land using specially designed equipment measuring spectral densities of wind and temperature at a single frequency indicates that present understanding of the Kolmogorov and flux/gradient relationships is adequate for the purpose. Although humidity spectra are included in the treatment, no measurements of them were made. Values of the effective Kolmogorov constants for velocity and temperature are found to be 0.54 ± 0.03 and 0.71 ± 0.04 respectively, in good agreement with other recent determinations.The principles of application of the technique at sea are discussed. The method assumes that the divergences of the eddy energy fluxes can be neglected. Whilst the present results appear to support this assumption, there is a need for further examination of this aspect.
Time spectra and cross‐spectra of kinetic energy in the planetary boundary layer
Authors: Hess G. D. , Clarke R. H. 
Published: February 2007

AbstractTemporal spectra and cross‐spectra of the three turbulent wind components for meso‐synoptic scales at 250 m vertical intervals in the planetary boundary layer are presented. The data were derived from hourly simultaneous balloon ascents from a 5‐point grid at Hay, New South Wales, Australia (lat. 34 ½S), during the Wangara expedition. The spectra indicate a meso‐scale gap for u (eastward component of wind) and v (northward component). The computed w‐spectra suggest that no marked gap is present. For periods less than 1 day the u‐ and v‐spectra, with a correction applied for high frequency noise, fall off approximately as n−2·6, where n is the frequency, and this result appears to be invariant with height within and just above the planetary boundary layer. The corrected w‐spectra exhibit n−1 dependency in this frequency range. The uv, uw, and vw cospectra also show only small contributions on the meso‐scale (periods less than a day) compared to the synoptic scale, indicating that meso‐scale motions may not have to be explicitly modelled in atmospheric general circulation models. An inertial peak is found for u and v but the w‐spectra show a diurnal peak. The phase angles showed that u and v were in approximate quadrature at the inertial frequency, demonstrating the existence of the inertial cycle. Tests for horizontally two‐dimensional isotropy indicated that the turbulence did not obey this simplification.
The Leipzig wind profile and the boundary layer wind‐stress relationship
Authors: Carson D. J. , Smith F. B. 
Published: February 2007

AbstractSwinbank's recent claim that Mildner's so‐called Leipzig wind profile data for the atmospheric boundary layer support the hypothesis that the shearing stress vector and the wind vector are parallel, is critically examined and compared with the conflicting classical hypothesis that stress and velocity shear are parallel as previously applied by Lettau. The geostrophic wind direction, known only imprecisely from Mildner's measurements, is allowed to vary in order to produce best‐fit profiles consistent with each hypothesis and generally accepted ‘boundary’ conditions. The degree of fit (theory to measurements) is roughly ten times better in the classical case than in Swinbank's case, the former showing a r.m.s. angular difference between the stress and shear vectors in the lowest 800 m of only 2°.
Non‐precipitating cumulus convection and its parameterization
Authors: Betts A. K. 
Published: February 2007

AbstractThis paper discusses the thermodynamic transports of heat, liquid water and (briefly) water vapour by non‐precipitating cumulus convection. It is shown that because of the irreversible mixing between cloud and environment, there is a downward transport of enthalphy in the cumulus layer. A lapse‐rate adjustment model relates stratification to the life‐cycle of a model cloud parcel. A sub‐cloud layer model specifies the lower boundary of the lapse‐rate model, and the convective transports through cloud‐base. Budget equations together with the lapse‐rate model, and its time dependent boundary conditions, predict the time development of the cumulus layer, and show the dependence on large‐scale mean vertical motion, cloud‐base variations, and the surface sensible heat flux.
On the summer hemisphere Hadley cell
Authors: Schulman L. L. 
Published: February 2007

AbstractIn the extreme seasons the winter hemisphere Hadley cell dominates the entire zonally averaged mean meridional circulation by extending well into the summer hemisphere, and the summer hemisphere Hadley cell practically disappears. The hypothesis that this apparent disappearance is due to the process of zonal averaging, and that a summer hemisphere Hadley cell does exist when the averaging is restricted to the longitudes not occupied by the Asiatic monsoon, is tested. Using data for 1957–1964 covering the months June‐August, it is found that the summer hemisphere Hadley cell was indeed present over the longitudes 160°E‐0–30°E, or two thirds of the Tropics. It is argued that some of the most interesting features of the meridional circulation and their associated transport processes are obscured by the zonal averaging process.
The laminated structure of the ozone in the atmosphere
Authors: Dobson G. M. B. 
Published: February 2007

AbstractOzonesonde ascents have shown that frequently the vertical distribution of the ozone in the stratosphere is very complicated with strong maxima and minima. Such a complicated distribution was not expected. In an attempt to find the cause of this highly laminated structure of the ozone, the variations in the intensity of the lamination with both season and latitude have been studied. It is found that a highly laminated structure is most frequent in spring and in the higher latitudes. It is also shown that well marked minima in the vertical distribution of the ozone are found at a height of about 15 km. The frequency of occurrence of these minima is also greatest in spring and in the higher latitudes. It is suggested that the ozone‐weak air in these minima has entered the stratosphere at the sub‐tropical tropopause break and has been carried polewards. A region of minimum ozone is also sometimes found at heights of around 23 km but less frequently than at 15 km. These high level minima are only found in late summer or autumn and in very high latitudes.
A simple theory of certain heliacal and anthelic halo arcs. The long hexagonal ice prism as a kaleidoscope
Authors: Tricker R. A. R. 
Published: February 2007

AbstractG. H. Liljequist and J. R. Blake have both recorded anthelic halo arcs on several occasions in Antarctica, with the sun at comparatively low elevations, which exclude on some occasions, and almost exclude on others, the mechanism put forward by Alfred Wegener to account for such arcs. A particularly complete display reported by J. R. Blake enables these arcs to be identified with those predicted by a very simple theory giver in the following paper, to which are added some remarks about the formation of an anthelion.
Momentum, heat and water vapour transfer to and from natural and artificial surfaces
Authors: Garratt J. R. , Hicks B. B. 
Published: February 2007

AbstractRecent atmospheric and wind tunnel data on the heat, mass and momentum transfer above natural and artificial surfaces indicate a general increase in the quantity kB−1 (= In(zo/zp), where zp is the roughness length appropriate to the quantity p) between aerodynamically smooth and fully rough flow. Below a roughness Reynolds number, u*zo/v, of about 100, kB−1 appears to be a single valued function of u*zo/v, closely approximated by the assumption of a molecular sub‐layer for heat and water vapour fluxes. Beyond u*zo/v = 100, there is no unique value of kB−1, but rather the observations suggest that the behaviour falls into either of two categories. For surfaces comprised of arrays of widely spaced solid roughness elements, kB−1 continues to increase (with some evidence for a plateau being reached by about u*zo/v = 1,000, when kB−1 ≃ 10), whilst for surfaces comprised of randomly distributed fibrous roughness elements, kB−1 gradually decreases with increasing roughness Reynolds number beyond about 100.
A note on the spectra of wind velocity components in the surface layer
Authors: Shárán V. Kr. , Wickerts Sture 
Published: February 2007

AbstractResults of our recent investigation of spectral measurements of wind velocity in the surface layer are analysed in light of the hypothesis proposed by Kaimal et al. (1972). It is confirmed that in the inertial subrange the spectra for all the three components and varying stability converge to a −2/3 line at the high frequency end. At the low frequency end the spectra cluster together in random fashion in a certain bandwidth and do not show any ordered arrangement with z/L.
Central England temperatures: Monthly means 1659 to 1973
Authors: Manley Gordon 
Published: February 2007

AbstractAn up‐to‐date Table is provided of the monthly and seasonal means representative of the air over central England from 1659 onward, incorporating some minor revisions and extensions of the earlier Table (Manley 1953 and 1959). Comments on its construction, and on the prospect of further extension backward in time, are added.