bluuebunny/crossref_metadata_2025_split huggingface dataset:
Turbulence measurements over the sea by a tethered‐balloon technique
Authors: Thompson N. 
Published: February 2007

AbstractTurbulent fluctuations of wind, temperature and humidity at heights up to a few hundred metres have been measured over the open sea by instruments supported by a tethered balloon. Wave‐induced motion of the ship from which the balloon was flown produced unwanted contributions to the measured turbulence, but in light or moderate winds it has been possible to make allowances for these effects and to obtain useful estimates for vertical fluxes of heat and moisture: the calculated momentum fluxes in contrast appear less reliable and to obtain satisfactory values will require stabilization of the tethering point of the balloon cable. Some observations made in generally unstable conditions near OWS ‘J’ yield a value of (1.8 ± 0.7) × 10−3 for CE in the bulk aerodynamic formulation for evaporation (E = ρCE (q0 − q10)(U10 − U0)) and suggest that compared to the vertical moisture flux the heat flux may often have an insignificant rǒle in determining the buoyancy flux and hence the turbulence structure in the bulk of the boundary layer.
Airborne dust collections down the Atlantic
Authors: Parkin D. W. , Phillips D. R. , Sullivan R. A. L. , Johnson L. R. 
Published: February 2007

AbstractThe airborne dust concentration in the Atlantic varies from 102μg/m3 of air near the Sahara coast to as little as 10−5μg/m3 over the Antarctic ‐ for particles > 0.5μm diameter.Dust collector meshes have been exposed on the bows of a ship (February‐March 1971) during the outward and return voyage between the Canary Isles and the River Plate. There is an order of magnitude change in concentration on crossing the Equator around 30°W. The dusts south of the Equator are borne on the south‐east trades and probably come from the Namib desert; their particle sizes are smaller than those coming from the nearer Sahara desert. The colour of the dusts on either side of the Equator are grey due to an admixture of black humus; off the Sahara coast they are brown and clean‐looking. The quartz to clay ratio increases with nearness to land but the kaolinite to illite ratio is symmetrical about the Equator, the savannah lands being rich in kaolin. Daily satellite photographs clearly show veils of dust crossing the coast at Dakar and some attempt has been made to relate these to the ship‐borne collections.
Inexpensive instruments for the measurement of solar radiation
Authors: Smith G. W. 
Published: February 2007

AbstractFour inexpensive solarimeters were compared with a standard. Mean errors (on a daily basis) were 5 per cent for the Gunn‐Bellani, 9 per cent for the Campbell‐Stokes, 10 per cent for the bimetallic actinograph and 12 per cent for the Sol‐a‐Meter. The corresponding weekly errors were 2–5 per cent, 3 per cent, 3.5 per cent and 4.5 per cent. A fifth instrument was not included because daily totals were difficult to obtain.
A numerical experiment using a general circulation model of the atmosphere
Authors: Gilchrist A. , Corby G. A. , Newson R. L. 
Published: February 2007

AbstractThe general circulation model whose formulation is described in Corby et al. (1972) was integrated for 60 days from real data with January radiation and sea surface temperatures. The deficiencies of the model as a representation of the atmosphere were revealed by the extent and rate of the systematic changes as an equilibrium state was approached. For the first ten days, the model lost eddy kinetic energy, then gradually recovered and from about day 30 its tropospheric simulations both synoptically and in its time‐mean cross‐sections at various longitudes, had many realistic features; it failed, however, to maintain a substantial Siberian winter anticyclone. A major weakness, resulting from the use of a single level to represent the 0–200 mb layer, was the progressive deterioration of the model stratosphere.
Stereo photogrammetry of cumulonimbus clouds
Authors: Warner C. , Renick J. H. , Balshaw M. W. , Douglas R. H. 
Published: February 2007

AbstractA technique is described for stereo photogrammetry of clouds. Movie cameras are set up on a ground baseline 5·6 km long. Time‐lapse films are made with a frame interval of 3 s. The analysis involves the super‐imposition of stereo pair images of the cloud, with advantages over methods previously used.Measurements are presented of an Alberta hailstorm, and estimates are made of horizontal divergence near the cloud tops, and mass flux. Measurements and calculations imply that the ring vortex model of the circulation in small cumulus tops is applicable to some large hail‐bearing storms, and that little or no net mass transfer occurs through the caps of rising cloud towers.
Equatorial Kelvin waves at 100 millibars
Authors: Parker D. E. 
Published: February 2007

AbstractA marked oscillation with a periodicity slightly greater than a month occurred in the zonal wind at 100 mb over Gan (00°41′S, 73°09′E) through the months January to May 1966. Corresponding oscillations took place during this period over other equatorial stations round the globe, but on the whole the oscillations became weaker with increasing latitude. The meridional wind was not directly involved in the oscillations, which were manifestations of a wave which generally progressed eastward relative both to the earth and to the mean flow with, however, a somewhat irregular rate of progression. The wave had zonal global wave number 1. Although it also advanced southward over the eastern hemisphere, it was not far from being symmetrical (as opposed to antisymmetrical) about the Equator. It was largely confined to the region between 150 mb and 70 mb, but it generally propagated downwards, Over the eastern hemisphere the 100 mb temperature tended to lead the 100 mb zonal wind by about 1/4 cycle. At least over Gan the 100 mb height and the 100 mb zonal wind tended to be in phase. The effect as a whole was sufficiently like an equatorial Kelvin wave to be considered as such. especially over the eastern hemisphere.The wave was linked very indirectly to concurrent events at 100 mb at 40°N. Less marked equatorial Kelvin waves occurred at 100 mb in 1960, 1967 and 1969. The incidence of equatorial Kelvin waves at 100 mb did not appear to be closely related to the phase at 50 mb of the tropical quasi‐biennial zonal wind oscillation.
Structure of low‐level jet streams ahead of mid‐latitude cold fronts
Authors: Browning K. A. , Pardoe C. W. 
Published: February 2007

AbstractSeveral case studies are presented showing the structure of ana‐cold fronts over the British Isles. One of the cases is analysed in detail using data acquired on the Isles of Scilly to avoid any confusing effects due to topography. All of the fronts described are characterized by a narrow band of shallow but vigorous convection at the surface cold front; this convection is essentially two‐dimensional and is termed line convection. In each case the line convection is bounded on its forward side by a low‐level jet reaching 25 to 30 m s−1; behind the line convection the winds decrease abruptly. The low‐level jet is embedded within a ‘convective boundary layer’, reaching its maximum velocity at 900 to 850 mb, and it consists of a tongue of anomalously warm, moist air, which has had a trajectory over an even warmer sea.It is shown that the line convection can be regarded as part of a mesoscale ‘right‐hand corkscrew circulation’ within the low‐level jet. The line convection constitutes one flank of the jet; it is characterized by very strong cyclonic shear and is fed by frictional convergence of air from beneath the jet core within the lowest 100 mb. Some of the air which ascends within the line convection subsequently flows forward and gently subsides within the upper part of the low‐level jet as part of the corkscrew circulation; however, most of the air which ascends within the line convection is extruded from the boundary layer and ascends in a rearward direction as slantwise convection above the inclined cold frontal zone. Precipitation grown in the slantwise convection falls into the cold air behind the surface cold front and the heat sink resulting from the partial evaporation of this precipitation probably accentuates the sharpness of the boundary of the low‐level jet at the surface cold front.
Balance of kinetic energy in the tropical circulation over the Western Pacific
Authors: Kung E. C. 
Published: February 2007

AbstractThe balance of kinetic energy in the large‐scale disturbances and general flow of the tropical circulation was investigated with special Marshall Islands upper‐air network data during 1958.The cross‐isobaric generation of eddy kinetic energy has two maxima: in the lower boundary and in the upper troposphere. However, the intensity of generation is about one to two orders of magnitude smaller than that in synoptic disturbances in the middle latitudes. A major portion of the generated eddy kinetic energy is exported outside the area. The space eddies are shown to derive a significant amount of kinetic energy from the kinetic energy reservoir of the basic flow in the area. The eddy kinetic energy is mainly dissipated in the lower boundary. There is a small amount of eddy dissipation in the upper troposphere. However, as a whole the free atmosphere provides very little damping to the disturbances through eddy dissipation.The kinetic energy balance in the general flow is determined mainly by the cross‐isobaric generation of kinetic energy and the dissipation term. The vertical distribution of the cross‐isobaric generation shows there is a large internal source of kinetic energy in the tropospheric easterlies and the kinetic energy is destroyed adiabatically in the upper‐level westerlies and easterlies. The vertical profile of the dissipation closely follows that of the generation. Examination of the dissipation term obtained as the residual term of the kinetic energy equation suggests that processes of different scales of motion are significantly involved in the kinetic energy balance of the observed scale.
Mesoscale air motions derived from wind finding dropsonde data: The warm front and rainbands of 18 January 1971
Authors: Roach W. T. , Hardman M. E. 
Published: February 2007

AbstractA diagnostic dynamical study is presented of the three‐dimensional field of motion based on data from dropsondes released through the warm‐frontal rainband situation of 18 January 1971, and is complementary to an earlier radar‐synoptic study of this situation.Principal features of interest are:

The identification of two low level jets. The first (axis below 1km) lies just ahead of and parallel to the surface warm front. The second (axis near 2km) overrides the first at an angle of about 50° and may be a continuation of the cold front jet overriding the warm front just ahead of the point of occlusion. The flow in the lower jet appears to be supergeostrophic; in the upper jet slightly subgeostrophic.
A distinct mesoscale perturbation of the synoptic scale wind field associated with the rainbands above the warm front. Large negative values of the vertical component of absolute vorticity were observed in the main rainband.
The mesoscale fields of motion produce a marked ‘peak’ in the spectrum of horizontal and vertical kinetic energy.
These and other features are discussed in relation to the results of a model of frontogenesis by B. J. Hoskins. Possible causes of the circulation associated with the rainbands and the interaction with other scales of motion are considered.
Turbulent diffusion within a wheat canopy: I. Measurement using nitrous oxide
Authors: Legg B. J. 
Published: February 2007

AbstractA new method is described for measuring the vertical component of the coefficient of turbulent diffusion, K, within a wheat canopy. A uniform controlled flux of nitrous oxide was released from a network of nylon tubes at ground level, and K was calculated from the concentration gradient measured at the centre of the network.The method was first used above the canopy when the crop was short, and the results agreed with those obtained from the wind profile and energy balance. Experiments with different sizes of distribution area showed that in most conditions a radius of only 12m was adequate to give a vertical flux that was constant within 15% to a height of 1m in a canopy 1·25m tall.The possible error in K was estimated to be 10 to 15% in the lower half of the canopy increasing to 30 to 40% above 1·0m. This is a useful complement to the energy and momentum balance methods that are very inaccurate in the lower half of the canopy.
Momentum transport by the thermal tide in the stratosphere of Venus
Authors: Plumb R. A. 
Published: February 2007

AbstractThe response of a stratified Boussinesq fluid subjected to a moving periodic thermal forcing is analysed and the role of thermal stratification in the generation of a mean ‘zonal’ motion discussed. In the parameter range where the phase speed of this forcing is much less than the speed of the gravest gravity wave mode, the problem may be treated as one of momentum transport by damped internal gravity waves, though the analysis does not require that the damping be small. Results from a simple model show that mean flow speeds much larger than the speed of heat source motion can be generated by this mechanism. Whilst, in the parameter range appropriate (to the best of our present knowledge) to the stratosphere of Venus, some assumptions of the analysis are violated, it is argued that mean winds of the order of 100m s−1 may be generated, thus supporting the suggestion of Schubert and Whitehead that this mechanism is responsible for the observed four‐day rotation of that planet's equatorial stratosphere. It is shown that the ratio of mean wind velocity to the speed of the subsolar point is independent of the length of the solar day, and that it is largely determined by the distribution of radiative heating and cooling in the planetary atmosphere.
Hemispheric coupling ‐ evidence of a cross‐equatorial planetary wave‐guide in the stratosphere
Authors: Barnett J. J. 
Published: February 2007

AbstractTemperature measurements at stratopause levels made by the Selective Chopper Radiometer on the Nimbus 5 satellite have been used to study the wavenumber‐one component of the near‐stationary eddy field. Sixteen months of data are presented. Tropical amplitudes underwent a 6–month oscillation, being small (<0·2 K) near the solstices and large (∼0·6 K) near the equinoxes when the large eddies associated with winter were simultaneously present in both hemispheres. The direction of meridional phase tilt and the continuity of phase across the equator suggest that at these times a wave was able to propagate from the more active to the quieter hemisphere, reaching 30° latitude or more. These results fit with the simple theory that stationary planetary waves propagate only when the wind is westerly, since wind at these levels is westerly over the whole globe only near the equinoxes.
The interpretation of the crystalline and air bubble structures of hailstones
Authors: Macklin W. C. , Carras J. N. , Rye P. J. 
Published: February 2007

AbstractThe factors which determine the crystalline and air bubble structures of accreted ice have recently been elucidated. It is now possible to ascertain the growth histories of hailstones of approximately spherical symmetry from studies of their internal structure. In principle this analysis can be extended to oblate hailstones once their aerodynamic behaviour is known. Six large hailstones 4 to 6.5cm maximum dimension, two from each of three severe storms, have been analysed. The orientation distributions and sizes of the crystals in the hailstone layers indicate that most of the growth of the hailstones took place at ambient temperatures between about −20 and −25°C, i.e. between 2.7 and 3.7km above the freezing level. The air bubble concentrations and size distributions show that all the hailstones grew with surface temperatures ranging from −1°C for the clear layers to about −11°C for opaque layers comprised of very small crystals. Heat balance considerations indicate that the effective liquid water concentrations in which the hailstones consequently grew were between 3 and 1g m−3. On the assumption that the median volume radius of the cloud droplet distribution was 10μm, the growth of most of the hailstones took place in liquid water concentrations of about the adiabatic values. However, fluctuations in the liquid water concentration of up to some 30% are required to explain the observed air bubble and crystal structures. The fact that the hailstones grew largely between the −20 and −25°C levels indicates that they were balanced in the updraught for most of their history. Since the hailstone fallspeed increases with radius, this meant that the updraught experienced by the hailstone increased steadily with time. There are two possible explanations for this: the strength of the updraught could have increased with time; alternatively, the hailstones could have moved around the main core of the updraught to encounter increasing updraught speeds, as suggested in the Browning and Foote (1975) three‐dimensional model of severe storms.
Extremizing downwind concentration of pollutants from plane area sources
Authors: Ailam G. , Neumann J. 
Published: February 2007

AbstractGiven is a horizontal plot of land P, a fraction of the area of which is assigned to an activity that produces air pollution. The latter area will be denoted S (source). Although the fraction of P allocated to S is fixed, we are otherwise free to determine the location and shape of S within the confines of P. Also given is either a second piece of land or a finite set of points in the same horizontal plane as P. That second piece of land, or set of points, will be denoted R (receptor). We assume that: the source strength density is steady and uniform across S; the wind and the turbulence are likewise steady and uniform along horizontal planes. We now wish to determine the shape of S and its location within P so as to minimize, or to maximize, the average pollution concentration in air at R due to S. By providing a duality principle and applying it to the present case, we show that the bounding curve of S is fixed by a concentration isopleth ‘associated’ with a hypothetical area source represented by R and the given boundary of P. The isopleth of concern is the one that encloses the prescribed area of S within the limits of P. Further, it is pointed out that the case of maximization is ordinarily simpler than that of minimization. In some cases S is not ‘connected’.Examples are given for the application of the theoretical results.
Response of the atmosphere to a tropical Atlantic ocean temperature anomaly
Authors: Rowntree P. R. 
Published: February 2007

AbstractObserved tropical Atlantic temperature anomalies for January 1963 have been used in a hemispheric model in an attempt to assess the extratropical effects of a tropical ocean temperature anomaly and to compare them with the results of previously reported experiments on tropical forcing. Falls of surface pressure were obtained over the warmed tropical water and extended north at least to 60°N over the east Atlantic, the northward limit of the falls varying considerably between three 80‐day experiment pairs as was to be expected from the tropical forcing experiments. The maximum amplitude of the mid‐latitude response (up to 7mb) was also consistent with that expected. One of the three experiment pairs produced an Atlantic pressure anomaly pattern similar to the average for the winter (1962–1963) in which the ocean anomaly was observed. The model is shown to give results which compared well with observations in winters with anomalous tropical Atlantic temperatures.
Cloud top heights from temperature sounding instruments
Authors: McCleese D. J. , Wilson L. S. 
Published: February 2007

AbstractA method for deriving cloud top heights using satellite remote temperature sounding instruments is described. The weighting functions of a 15μm CO2 tropospheric temperature sounder are modified by the presence of cloud in the sounding column. The relative effect of cloud on two or more such weighting functions in successive soundings along an orbital or scanning track is shown to be a simple function of cloud height. The method permits cloud heights to be found without the need to derive cloud amount. Results from the Nimbus 5 Selective Chopper Radiometer are presented.
Profiles and evaporation
Authors: Penman H. L. , Long I. F. 
Published: February 2007

AbstractIt is suggested that in all conditions of stability either of two slightly different profile equations can be used, both carrying in‐built stability weighting factors for use in transport equations. Setting Λ = In(z—d)/z0 the more convenient equation for field use is u = S0 Λe−nΛ/2, where n is dependent on stability (+ in lapse, — in inversion): the important assumptions in physics are that d and z0 are surface constants, and that S0 = u*/k for all values of n, as it is for n = 0. For other values of n, the standard plot of vn̈. In(z—d) has a slope, S ( = du/dΛ), at some average values ū, λ, and backward extrapolation to Λ = 0 gives an intercept ui such that ui/ū = nλ/2 = y. The weighting factor for the shear, f = S0/S, thus becomes ey/(1—y). To find y, u/ū is plotted against U, where U is the velocity measured in a neutral period. No knowledge of temperature gradient is needed – other than ability to recognize when it was near enough to zero to be able to pick out U, z profiles. Because λ appears in y, the roughness length, z0, does not vanish: in effect, it replaces the extra ‘length’ that is put into other stability weighting factors – not needed here.Profiles of wind, temperature and humidity above and within two large plots of kale (one irrigated) are studied in detail for short periods of strong lapse and strong inversion, first to show the high quality in anemometry needed to exploit the profile equation (barely achieved on the north plot, and not on the other); second, to demonstrate a way of correcting for zero errors in the thermometry: and, third, to show that above the crop the profiles of wind and water vapour pressure have the same shape, and the Bowen ratio is invariant with height. Within the crop, in both lapse and inversion, the top of the crop is the source or sink for sensible heat transfer. In a humidity inversion, the top is also the sink for latent heat transfer, but in a lapse the source is at, or close to, the virtual sink for momentum at z = d+z0.Evaporation from the north (unirrigated) plot was calculated for 44 days (27 June to 8 August 1971), each day's total being the sum of six estimates for 4‐hour periods. Two weighting factors were used: first, a factor ϕ, based on Richardson number; second, the factor f2. The 44‐day totals were 128mm (using ϕ; identical with calculated potential evaporation), and 137mm (using f2). More detailed study of 13 days in the period (using f2) showed that in the diurnal cycle, evaporation, on average, is zero in the eight hours of darkness, very small from 04 to 08h, large from 08 to 16h, and moderate from 16 to 20h. The energy balance is satisfactory. Comparison of Bowen ratios over the two plots indicated that E(irrigated)/E(unirrigated) was about 1.06. A direct comparison (neutron moisture meter) gave a ratio near 1.10. (The absolute values are suspect.)