bluuebunny/crossref_metadata_2025_split huggingface dataset:
Charge transfer accompanying individual collisions between ice particles and its role in thunderstorm electrification
Authors: Gaskell W. , Illingworth A. J. 
Published: February 2007

AbstractExperiments were conducted with a wind tunnel in a cold‐room in order to investigate the individual charges transferred when ice spheres collided with an artificial hailstone. The charge transferred to a sublimating hailstone was negative and had a magnitude proportional to the velocity of impact and to the diameter of the ice sphere to the power 1.7. The charge transferred when 100μm diameter ice spheres collided with the hailstone at a velocity of 8ms−1 was typically –15 fC. No variation of charging could be detected over the temperature range –5 to –25 °C, or when the ice was doped with impurities, or when hailstones of different surface roughness were prepared.Hailstones which were cooled below the ambient cold‐room temperature and subsequently grew by deposition, charged positively by typically 100 fC per collision. However, a hailstone which was cooled by the same amount but was maintained in a sublimating condition charged negatively. These experiments show that thermal effects did not play a direct role in the charge transfer process. Experiments were performed with a riming hailstone in order to simulate the conditions found in a natural cloud. The hailstone charged positively at temperatures of –5°C and –10°C and negatively at –15°C and –20°C with liquid water contents in the range 0.05 gm−3 to 0.85gm−3, the magnitudes of the charges being typically 30 fC.It is suggested that the charge transfer occurs from one ice surface to the other at the contact interface and that the driving force for the charge transfer at the contact interfaces is the different surface potentials and/or different charge carrier densities of ice surfaces formed in different ways. It is possible that the charge carriers may be surface ions of a liquid like layer on the ice surface.The results with the riming hailstone are consistent with thunderstorm observations that the negative charge centre is above the –10°C isotherm and that, although precipitation particles are predominantly negatively charged, a mixture of signs is usually present.
Tropospheric gravity waves: Their detection by and influence on rawinsonde balloon data
Authors: Lalas D. P. , Einaudi F. 
Published: February 2007

AbstractIn this paper we discuss the interaction of a tropospheric gravity wave, detected by a radar and a microbarograph array, with a normal rawinsonde balloon. By calculating the wave properties and comparing them to balloon data, we show that such data can provide information about tropospheric gravity waves. We also draw attention to the consequences of the wave‐induced differences between the measured and the actual background state of the atmosphere. The differences may be critical, for example, in predicting clear air turbulence and in evaluating remote sensing instrumentation.
The simulation of a fair weather marine boundary layer in GATE using a three‐dimensional model
Authors: Nicholls S. , Lemone M. A. , Sommeria G. 
Published: February 2007

AbstractA detailed three‐dimensional model has been used to simulate a cumulus‐topped tropical oceanic boundary layer. A particularly dense set of observational data from surface‐based and airborne instrumentation collected during one day of the GARP Atlantic Tropical Experiment (GATE) has been used enabling comprehensive initial and boundary conditions to be specified. This also permits detailed comparisons to be drawn between the model and observations.The model is found to reproduce the structure of the observed undisturbed boundary layer quite realistically. The clouds developed in the model are similar to those observed in both amount and physical size and the modelled turbulent fluxes in the subcloud layer agree well with observations. Also, the evolution of the modelled boundary layer is similar to that in which the observations were made. The model confirms that the major effects of the turbulent mixing are to warm the subcloud layer but to moisten and cool the cloud layer. The limited scale of the model (2 km x 2 km x 2 km) does, however, lead to systematic differences between measured and modelled variances.The model's turbulent kinetic energy balance for the coupled cloud‐subcloud layers is presented. Although reliable measurements are only available in the subcloud layer, they confirm that the model's values are qualitatively correct except when very close to the bottom boundary.The model's temperature and humidity profiles are strongly affected by mixing occurring across cloud‐base throughout much of the subcloud layer. This is reflected in the shape of the θv profile which displays a characteristic minimum midway through the subcloud layer. When scaled using cloudbase parameters, the resulting profiles are similar to those obtained in more unstable conditions over land.
Comparison of some different approximations in the statistical theory of relative dispersion
Authors: Sawford B. L. 
Published: February 2007

AbstractThe effect on the theory of relative dispersion of some different approximations to the two‐particle Lagrangian correlation function is examined. Two of these, one due to Taylor, the other to Smith and Hay, are treated in detail.Through numerical solution of the dispersion equations, the influence of the initial cluster size, a number of simple variations of the spatial separation argument of the two‐particle correlation function, the number of particles in the cluster and the ratio of Lagrangian to Eulerian integral scales are examined. With the exception of the initial cluster size, which is important in the early stage of growth, these parameters are relatively unimportant, particularly compared to the overall difference between the two approximations.In qualitative agreement with Batchelor's inertial range theory, both the Taylor and Smith‐Hay approximations show linear growth at small time with an accelerated growth region at intermediate time. However, between these regions, the Smith‐Hay solution shows a region of less‐than‐linear growth for which there appears to be no observational or theoretical support. This regime is more pronounced, and the difference between the two approximations greater, for initially small clusters.Comparison with suitably documented observations, while not entirely definitive, shows a degree of consistency and suggests the Taylor approximation to be the more appropriate.
A study of the earth's radiation budget using a general circulation model
Authors: Slingo Julia M. 
Published: February 2007

AbstractObservations by satellites have shown that the various components of the global mean radiation budget have a significant seasonal variation, the causes of which are not properly understood. Results from an annual cycle integration with the Meteorological Office 5‐level general circulation model have been used to clarify the roles played by clouds and the surface in determining the seasonal variations in the radiation budget. The model uses an interactive radiation scheme with seasonally varying climatological sea surface temperatures, incoming solar radiation and zonal mean climatological cloud amounts. Its simulation of the various components of the earth's radiation compares favourably with results from satellites and it has therefore been possible to use its results to explain some aspects of the observed budgets.Many of the features of the annual cycle of the global mean radiation can be associated with the asymmetry in the distribution of land and sea between the two hemispheres. Variations in the global mean planetary albedo can be attributed partly to the illumination of Antarctica near the solstice and partly to the southwards spread of winter snow cover over the northern hemisphere continents. For the globe as a whole variations in cloudiness have little effect. The main determinants of the global mean outgoing flux appear to be the surface and associated tropospheric temperatures. Since the seasonal change in the surface temperatures of the land masses of the northern hemisphere is greater than that of the extensive oceans of the southern hemisphere, the variation in the global mean outgoing flux is dominated by that in the northern hemisphere. Again the effect of seasonal variations in cloudiness is small.The model results have also been used to estimate the earth's annual mean total energy budget and, in particular, the poleward flux of heat by the oceans. The oceanic heat flux implied by the model compares quite favourably with estimates based on observations, the main differences being at the equator and near the North Pole. The model gives a cross‐equatorial oceanic flux from the southern to the northern hemisphere and a significant flux of heat by the oceans into the Arctic Basin.
Moisture analysis of the A‐scale phase means during GATE
Authors: Huang Huo‐Jin , Vincent Dayton G. 
Published: February 2007

AbstractA moisture analysis, based on GATE A‐scale phase means, is presented for western Africa (land) and the eastern Atlantic (water) area. Vertically‐integrated moisture budget terms are calculated for the whole area, as well as for land, water and A/B ship array areas. Precipitation minus evaporation (P̄−Ē) is solved as the residual. Upward vertical motion, associated with organised convective disturbances and westward‐propagating waves, causes the vertical advection term to dominate. Over land P̄−Ē decreases slightly from Phase I to Phase III, whereas over water it increases greatly during the same time span. When the evaporation rate of 3.8mmd−1 from the Phase III B‐scale results of Thompson et al. (1979) is applied to our A/B scale results, it yields a precipitation rate of 10.8mmd−1. This compares favourably with the remotely‐sensed estimates of 12.7mmd−1 for the B‐scale array obtained by radar and 14.0mmd−1 for the A/B ship array derived from satellite observations. Furthermore, P̄−Ē in the GATE area is found to be considerably greater than the global estimate for approximately the same latitude band.
A Boolean approach to climate dynamics
Authors: Nicolis C. 
Published: February 2007

AbstractOne of the main characteristics of the climatic system is the existence of numerous feedback and jump phenomena. It is suggested that a discontinuous formulation based on Boolean logic can be fruitfully used to analyse this behaviour. The approach is first applied to simple examples, and the logical predictions are compared with the results of the more familiar continuous formalism. The qualitative insights that such an analysis can add are then illustrated on more complex situations.
The diurnal thermocline due to buoyant convection
Authors: Dalu G. A. , Purini R. 
Published: February 2007

AbstractA simple model, including solar radiation, surface colling and buoyant convective adjustment is used to study the temperature distribution in the uppermost layers of the ocean, assuming that the salinity is uniformly distributed and that wind mixing is negligible.It is found that the depth of convection cannot be identified with the thermal compensation depth: time dependent solutions show that the lags are such that equilibrium solutions may be misleading.
The diurnal variation of ozone in the upper stratosphere as a test of photochemical theory
Authors: Pallister R. C. , Tuck A. F. 
Published: February 2007

AbstractIt is argued that detailed consideration of the 24‐hour waveform of ozone in the upper stratosphere provides a means of testing current photochemical kinetic mechanisms, with measurements requiring good relative rather than good absolute accuracy. The implications of the pronounced changes with height of the waveform for remote sounding and monitoring are pointed out. Diurnal, semidiurnal and higher harmonics of ozone and temperature waveforms are obtained by Fourier analysis.
A study of meteorological patterns associated with a lake confined by mountains – the Dead Sea case
Authors: Segal M. , Mahrer Y. , Pielke R. A. 
Published: February 2007

AbstractA planned project to generate hydroelectric power by carrying Mediterranean water into the Dead Sea has stimulated a preliminary numerical model study of the regional meteorological patterns and the evaluation of some possible local climatic modifications. Predicted mesoscale meteorological patterns associated with two frequent synoptic conditions over the region are presented. Emphasis has been focussed on illustrating and studying two general aspects of the thermal circulations generated by a lake which is confined between mountains (LMC): the effect of external flows on the LMC structure and the effects of lake water temperature on the LMC intensity.
On the initial formation of deep fronts
Authors: Manton M. J. 
Published: February 2007

AbstractA perturbation analysis is used to describe the initial intensification of a baroclinic temperature field by the shearing action of an upper‐level transverse wave. The perturbation parameter ε is the ratio of the across‐front to along‐front length scales. The interaction of the horizontal shear of the large‐scale wave with the horizontal temperature gradient is found to generate a vertical velocity field, which is steady in time to O(ε2). Conditions are sought for the formation of anafronts and katafronts.
Diagnostics of hydrometeorological anomalies in the Zaire (Congo) basin
Authors: Hirst Anthony C. , Hastenrath Stefan 
Published: February 2007

AbstractInterannual variations in the large‐scale circulation over the tropical Atlantic are studied in relation to hydrometeorological anomalies in the Zairee (Congo) basin. Composite departure patterns of atmospheric and oceanic fields in the Atlantic are constructed for extremely dry and for extremely wet years in the Zaire river catchment. These maps are complemented by isocorrelate charts between river level and selected elements in 5° blocks of the Atlantic.Water levels of the Zaire river in the first and second halves of the year are positively related to sea surface temperature off Angola, and to humidity and to actual and convective instability at Luanda, approximately upwind from the Zaire catchment. However, lapse rates at the Angola coast are strongly controlled by upper air conditions: cold air aloft may enhance instability and thus rainfall. Unlike during the first semester, sea surface temperature anomalies during the second half of the year do not seem to be forced by prior behaviour of wind stress in the equatorial Atlantic, nor by local wind speed and cloudiness. Equatorial south‐westerlies flowing across the Angola—Gabon coast toward the Zaire catchment are strong/weak during second semesters of high/low water level. Rainfall over the Zaire basin appears to be modulated by a zonal circulation along the Atlantic equator.
A study of dewfall in an arid region: An analysis of wangara data
Authors: Hicks Bruce B. 
Published: February 2007

AbstractMicrometeorological flux‐gradient relations have been used to deduce average evaporation rates for most hours of the Wangara experiment, using net radiation and ground heat transfer values. At night, dewfall is found to have been a common occurrence, at rates that averaged about 0·015mmh−1 and sometimes approached (but never exceeded) the value of about 0·07mmh−1 that has been proposed as a natural limit. The average nocturnal dewfall was about 0·22 mm. During the 44 days of the experiment, about 20mm of rain fell at the central site, augmented by about 9mm of dewfall. Evaporation amounted to about 26mm of water.
Simultaneous measurements of the turbulent and microphysical structure of nocturnal stratocumulus cloud
Authors: Caughey S. J. , Kitchen M. 
Published: February 2007

AbstractObservations from tethered balloon‐borne instrumentation of small‐scale air motion, temperature fluctuations and microphysical structure occurring within nocturnal stratocumulus are presented and discussed. The cloud top was marked by a very sharp and thin inversion layer whose vertical displacement was monitored with an acoustic sounder. The velocity field indicates the presence of strong downwards convection within the cloud, in which radiatively cooled air is transported away from the region near cloud top in discrete plumes. Droplet data show the preferential location of larger cloud droplets (> 7 μm radius) within the convection cells. Some aspects of the droplet observations are explained in terms of a simple Lagrangian model. Although entrainment is excluded from the model the predictions are consistent with the observations. Entrainment effects at cloud top result primarily in droplet concentration fluctuations with little change in the shape of the droplet spectrum, which the model suggests is mainly determined by the effects of radiation on droplet growth by condensation and the effects of vertical motion. Finally, some characteristics of turbulence through the cloud layer, and boundary layer generally, are examined and related to observations from the cloud‐free convective boundary layer and data from laboratory experiments.
Preliminary results of an investigation of the spatial distribution of fog droplets by a holographic method
Authors: Kozikowska Anna , Haman Krzysztof , Supronowicz Jan 
Published: February 2007

AbstractHolograms of natural fogs have been made. A fog volume of 22·5 cm3 has been analysed from one hologram. Tests have been carried out to see whether the obtained spatial distribution of droplets could be approximated by Poisson statistics, mainly with negative results.A continuation of this type of research and a deeper theoretical study of the effects on coalescence processes of a non‐random spatial distribution of droplets is suggested.
A study of mesoscale convective bands behind cold fronts. Part II: Cloud and microphysical structure
Authors: Bennetts D. A. , Ryder P. 
Published: February 2007

AbstractThis paper reports observations made over the North Atlantic of a system of convective cloud bands found within the cold air behind an occluded front. The observations were made from an instrumented aircraft which also released a pattern of dropsondes, measuring temperature, humidity and wind as functions of pressure.The microphysical observations are interpreted by use of a three‐dimensional numerical model of deep convection with particular emphasis on the ice budget. The observations cannot be reconciled with a straightforward application of the theory of droplet freezing due to the activation of ice nuclei. Alternative freezing mechanisms involving the ingestion of the remnants of previously glaciated cloud and ice multiplication by the Hallett‐Mossop effect are considered.
Transfer coefficient eddy flux parametrizations in a simple model of the zonal average atmospheric circulation
Authors: White A. A. , Green J. S. A. 
Published: February 2007

AbstractBaroclinic eddy parametrizations of the type proposed by Green in 1970 are applied in a simple climate model which is the zonal average counterpart of the long wave model used by the authors in a recent paper. Three parametrization schemes, each with different specifications of transfer coefficients, are examined. Diabatic forcing is represented by a sinusoidal function of latitude, and the performance of each scheme is gauged by the realism of the eddy flux and zonal mean fields which it produces in the steady state. In broad agreement with numerical simulations of baroclinic eddy life cycles, the best results are obtained when a certain condition of maximum available potential energy release is relaxed. The main feature of the study is the systematic application of fundamental constraints on the eddy vorticity fluxes: these are used to determine free parameters in the functional specification of the transfer coefficients.
An update of the Arosa ozone series to the present using a statistical instrument calibration
Authors: Dütsch H. U. 
Published: February 2007

AbstractResults of the statistical method for determining and continuously adjusting the so‐called instrumental constants of two Dobson spectrophotometers operated in parallel for eight years at Arosa, Switzerland, are discussed. It is found that year‐to‐year variations of the constant are largely due to instrumental change and may have only a very slight contribution‘if any’from variations in the solar spectrum. Haze influence on the determination of the constants and on single wavelength ozone measurements is found; the latter has a strong seasonal variation. It is also found that the nickel sulphate filter used to eliminate stray light within the instrument has a small temperature dependence, which introduces a slight error in the determination of the instrumental constant with the filter and also in the measured seasonal variation of total ozone.The Arosa C wavelength total ozone series beginning in 1926 is extended to 1982. Secular variations during the last 20 years demonstrate a remarkable constancy of the C—AD difference. This establishes the validity of the statistical method for monitoring the instrumental constant. The haze‐produced seasonal variation of the C—AD difference has hardly changed during that period, showing that the haze influence on C wavelength pair measurements has hardly increased with time.
Further theoretical studies of the role of splintering in cumulus glaciation
Authors: Koenig L. Randall , Murray Francis W. 
Published: February 2007

AbstractThe hypothesis that rime splintering can account for the presence of more ice particles in certain clouds than active ice‐forming nuclei is tested in a group of numerical experiments using a cloud model incorporating dynamics and bulk microphysics. Both warm base and cold base clouds were simulated with several sets of microphysical parameters. A second part of the study examined the dependence of the rate of glaciation on the concentration of natural ice‐forming nuclei. It is found that inclusion of a splintering mechanism leads to simulations that are more in accord with field observation, especially as regards the sensitivity of ice crystal concentration and rapidity of glaciation to the early concentration of cloud droplets and the dispersion of their size distribution. The rate of glaciation is highly sensitive to the properties of the supercooled liquid phase and accordingly to cloud base temperature (rapid for warm base clouds, slow for cold base clouds) but insensitive to the concentration of natural ice‐forming nuclei.
Comments on paper ‘the effect of gaussian particle‐pair distribution functions in the statistical theory of concentration fluctuations in homogeneous turbulence’ by B. L. Sawford (Q.J. April 1983, 109, 339–353)
Authors: Egbert Gary D. , Baker Marcia B. 
Published: February 2007

AbstractIn this brief note we examine the necessity of distinguishing between the use of forward and reversed transition densities in the computation of second moments of concentration fields advocated by Sawford. In contrast to Sawford, we show that the forward densities are always correct and that for incompressible flow the forward and reversed formulations are equivalent. This equivalence implies a simple constraint on particle‐pair separation densities for incompressible flow.