bluuebunny/crossref_metadata_2025_split huggingface dataset:
Atmospheric opacity: A study of visibility observations in the British Isles
Authors: Wright H. L. 
Published: July 2010

AbstractA station may be classified as to visibility by using visibility frequencies to evaluate the atmospheric opacity, which is directly proportional to the extinction coefficient. Mean values of the atmospheric opacity in clear conditions and in foggy conditions at various stations in the British Isles are utilised to infer the contribution of the various types of nuclei and particles to the opacity, and in particular to infer the relative efficiency of each type as a fog‐producer.It is concluded that sea‐salt nuclei are much larger than combustion nuclei and play a leading part in the determination of visibility. The effect of combustion nuclei is negligible unless they are extremely numerous, but the concomitant smoke particles contribute largely to impairment of visibility and when plentiful may even produce thick fog.Water fogs are due to sea‐salt nuclei and if supersaturation is attained the fogs may thicken considerably owing to the deposition of water on the sea‐salt nuclei which consequently become very much larger. Such deposition does not occur on the combustion nuclei if sea‐salt nuclei are present.The variation in opacity with relative humidity is calculated theoretically and the calculations are applied to observations of nuclei, particles, and relative humidity at Kew Observatory in the afternoon. Fair agreement is found between the calculated values of opacity and those which correspond to the visibility observed.In one appendix to the paper factors are evaluated by which the visibility of reflecting objects viewed against sky or terrestrial backgrounds may be compared with the visibility of a black object silhouetted against the sky. In a second appendix the increase in opacity during precipitation is calculated.
A theory of organized steady convection and its transport properties
Authors: Moncrieff M. W. 
Published: July 2010

AbstractA dynamical classification of organized convection is presented, and previously published and additional models are collated in a more general theory. the transport properties of each type are represented by flux laws, the motivation being to understand convective transports in the context of parametrization schemes for organized convection.Five distinct models, derived as analytic solutions to a general displacement equation obtained from conservation properties of the Boussinesq equations, are necessary to describe the dynamics. These models, designated propagating, steering‐level, jump, cellular and classical, have very distinctive dynamical structures, and can be combined to represent more complex types of organized convection.The propagating and steering‐level types export a significant amount of kinetic energy, momentum and entropy, while the jump and cellular types store a considerable amount of energy as work done on the environment by the pressure field. the classical type does not transport momentum, and is a representation of the classical thunderstorm in weakly sheared flow.Apart from the cellular model, although the entropy transports are broadly similar, the momentum and kinetic energy transports are very distinctive, with counter‐gradient momentum transport the rule rather than the exception. Thus by effecting organized updraught/downdraught circulations, a completely different transport problem from small‐scale cumulus and mixed‐layer convection is posed, with fundamental inferences regarding parametrization. the dynamical necessity of a mesoscale response in the cellular and propagating types suggests that this scale may, in certain cases, need to be represented explicitly in convective parametrization schemes for large‐scale models.These prototypes have been deliberately simplified for the sake of elucidating fundamental principles, and to give a dynamical basis for experimentation and generalization, through exploiting both cloud‐scale and larger‐scale numerical simulation models, as well as providing guidance in observational analyses, budget studies in particular.
Measurement of boundary layer structure parameter profiles by acoustic sounding and comparison with direct measurements
Authors: Moulsley T. J. , Asimakopoulos D. N. , Cole R. S. , Crease B. A. , Caughey S. J. 
Published: July 2010

AbstractAcoustic sounder derived profiles of the atmospheric velocity and temperature structure parameters, Cv2 and CT2, are presented. the former is obtained using a novel bistatic acoustic sounder comprising a fan beam transmitter and a vertically directed receiver. Simultaneous profiles of the temperature structure parameter are obtained using a conventional monostatic sounder.Time histories of these quantities at two heights in the boundary layer are given and are compared with in‐situ measurements. the results indicate significant anisotropy in the temperature field at scales greater than a few metres and emphasize the care required when comparing directly measured and acoustically estimated turbulence quantities. the significance of anisotropy in the assessment of excess attenuation is also discussed.
The early evening boundary layer transition
Authors: Mahrt L. 
Published: July 2010

AbstractVarious mechanisms which lead to nocturnal accelerations and formation of the low‐level jet are examined by analysing Wangara data. the stress field is inferred from the wind field and equations of motion. the evolution of the stress divergence, during the evening transition from daytime mixed layer flow to nocturnal boundary layer flow, is found to increase the ageostrophic flow and subsequent nocturnal accelerations by roughly a factor of two. During this transition the stress divergence in the lowest few hundred metres increases due to the fact that the influence of decreasing boundary layer depth exceeds the effect of decreasing surface stress. This leads to temporary deceleration and rotation of the low‐level wind vector towards low pressure and thus increases the ageostrophic flow.Diurnal variation of the geostrophic wind is also found to significantly strengthen the nocturnal flow. This diurnal variation is apparently due to heating and cooling over terrain which slopes gently upward, east of the location of the Wangara experiment.
A computer simulation of the effects of differing crop types on the water balance of small catchments over long time periods
Authors: Sellers P. J. , Lockwood J. G. 
Published: July 2010

AbstractA multilayer crop model is used to simulate the interception and evaporation of rainfall as well as transpiration loss for a pine canopy. A considerable improvement, in terms of physical realism, over the Rutter (Rutter et al. 1971) model appears to have been achieved and the results generally agree with experimental work. Simulation runs on synthetic meteorological data indicate that the Rutter model substantially underestimates the interception loss from low intensity rainstorms. the multilayer pine model, MANTA, is run with a year's data and the results compared with those from an equivalent unilayer pine and also a grass model. the results show that MANTA predicts a 20% increase in interception loss over the Rutter model estimate and that over the year the interception loss from grass is one quarter of that from pine.
Parametrization of the ice‐phase in a model of mid‐latitude cumulonimbus convection and its influence on the simulation of cloud development
Authors: Bennetts D. A. , Rawlins F. 
Published: July 2010

AbstractThe three‐dimensional model of deep tropical convection described in Miller and Pearce (1974) has been extended by the incorporation of a parametrized ice phase. This parametrization is capable of describing two routes for the formation of precipitation, cloud water → cloud ice→hail and cloud water→rain→ hail, and these are investigated separately, Numerical simulations are then compared with an observational study of two cumulonimbi, one a single‐celled cloud and the other a multi‐celled storm. Special attention is paid to the growth of a daughter cell on one flank.
Spectral characteristics of surface layer turbulence over the sea
Authors: Nicholls S. , Readings C. J. 
Published: July 2010

AbstractAirborne measurements of atmospheric turbulence spectra and cospectra made at low levels in convective boundary layers over the sea around the UK are presented. Both along‐wind and across‐wind sampled data are considered. In general, the former agree well with the results of other workers obtained over the sea using surface based instrumentation, though their temperature spectra differ significantly. the present along‐wind data are also compared with corresponding results obtained over land. Again the velocity spectra agree closely but the temperature spectra differ appreciably. the along‐wind humidity spectra obtained over the sea closely resemble the over land temperature spectra. No corresponding measurements are available to compare with the across‐wind sampled spectra.Both along‐ and across‐wind spectra vary with stability, increases in convective activity being associated with increased energy at low wave‐numbers. No corresponding change was observed in the cospectra.A comparison of along‐ and across‐wind sampled spectra and cospectra reveals considerable differences. These are consistent with a redistribution of energy from high to low wave‐numbers on changing from across‐ to along‐wind sampling. Thus the across‐wind spectra and cospectra appear more narrow (by about one decade). Spectral and cospectral peaks are also shifted. These observations are consistent with the stretching effects of the mean velocity shear acting on convective elements.The dissipation parameters derived from the high frequency parts of the spectra appear quite reasonable though there is a systematic difference between those derived from vertical and horizontal velocity spectra.
Microphysical development of a pulsating cumulus tower: A case study
Authors: Keller Vernon W. , Sax Robert I. 
Published: July 2010

AbstractIn‐cloud microphysical data collected within a 22 minute period during seven consecutive passes at the −13°C sampling level of a deep (base +22°C) convective cloud provide observational evidence for a secondary ice production mechanism at work in the Florida environment. the observed microphysical characteristics of the convective tower, particularly the spatial distribution and habit of the ice phase relative to the updraught, are consistent with a rime‐splintering hypothesis for secondary ice production. It is shown that the cloud's updraught structure is critically important in governing the timing of the ice production by controlling the flux of graupel particles through the critical temperature zone (−3°C to −8°C). the importance of the cloud's pulsation growth dynamics on the microphysics is emphasized, particularly as it relates to rapidly glaciating cumuli.
Laboratory observations of the effects of topography on baroclinic instability
Authors: Jonas P. R. 
Published: July 2010

AbstractObservations are presented of the effects of topography on thermally driven baroclinic flows in a rotating annulus. It is observed that the transition from baroclinically stable to unstable flows is stabilized in the presence of small amplitude topography. However, when baroclinic waves are present they are of shorter wavelength and larger amplitude than those in flows driven by similar temperature differences in the absence of topographic forcing. Non‐linear interactions between stationary forced and drifting baroclinic waves may result in the appearance of significant amounts of energy in drifting waves which are not harmonics of the dominant baroclinic wave.A local linear analysis is used to explain the observations of the effects of topography on the onset of baroclinic instability. Despite the limitations of this analysis which arise due to the similarity of the wavelengths of the baroclinic and forced waves the quantitative predictions of the analysis are in reasonable agreement with the observations.
The interaction between an internal gravity wave and the planetary boundary layer. Part II: Effect of the wave on the turbulence structure
Authors: Finnigan J. J. , Einaudi F. 
Published: July 2010

AbstractAn atmospheric internal gravity wave was measured over a two‐hour period by a microbarograph array and a series of fast response wind and temperature sensors deployed along a 300m tower. the particularly monochromatic nature of the pressure signal at the ground enabled an explicit separation of the velocity field into mean, wave, and turbulent components. Large wave‐frequency fluctuations were observed in the turbulent Reynolds stresses. Their significance is discussed at length with special regard to their role in the budget of wave kinetic energy. It is shown that the quadrature relationship which they maintain with the components of wave‐shear, limits their effectiveness in reducing the wave amplitude. Analysis of the important time scales in the budget of turbulent kinetic energy reveals that the energy containing eddies have time scales longer than the wave period, and consequently the turbulence cannot remain in equilibrium with large, wave‐frequency fluctuations in shear production. the result is a boundary layer which never attains a true equilibrium state.
A laboratory study of the inductive theory of thunderstorm electrification
Authors: Gaskell W. 
Published: July 2010

AbstractThe individual charges transferred when supercooled water droplets or ice spheres collided with an artificial hailstone in the presence of an electric field have been measured in order to check the theoretical predictions of the inductive theory of thunderstorm electrification. the inductive theory equation was found to be obeyed for 100 μm supercooled water droplets, but droplet transit time measurements suggested that separation only occurred following equatorial collisions with the smooth hailstone. This greatly limits the maximum charge that the hailstone can carry, and so, if rougher natural hailstones behave in a similar manner, this process is not thought to be significant in thunderstorm electrification.The charge transfer measured when 100 μm diameter ice spheres collided at 8ms−1 with a hailstone was affected by the presence of radial fields, but the change was less than that predicted by the inductive theory. the charge transfer was independent of temperature between −5°C and −25°C although the conductivity of ice varies greatly over this range. the effect of the field was to broaden the histograms of charge transfer rather than shift them as a whole to greater or lesser values and the charge transfer was not symmetrical under the influence of positive and negative fields of the order of 100 kV m−1. These facts make the field dependent charging results difficult to explain purely in terms of the inductive effect.
Cyclone development in the south pacific convergence zone during fgge, 10‐17 January 1979
Authors: Vincent Dayton G. 
Published: July 2010

AbstractA diagnosis of the life cycles of three South Pacific cyclones, each tropical in origin, is presented. the study focuses on two of the cyclones which propagate south‐eastward along the western edge of the South Pacific convergence zone (SPCZ) and reach middle latitudes before decaying. Based on enhanced IR satellite imagery from GOES‐West, both cyclones appear to go through stages of development similar to those described by Troup and Streten, even though their classification system generally applies to higher latitude systems. the primary data set used for surface and upper air analyses is based on ECMWF FGGE level III‐b analyses. Variables presented include mean sea level pressure (m.s.l.p.), horizontal divergence, relative vorticity, and winds. A comparison between m.s.l.p. patterns obtained manually from station observations and those produced objectively by ECMWF shows good agreement except when the cyclonic disturbances are subgrid‐scale. Maximum low level convergence occurs in the SPCZ, north and east of the cyclone tracks; however, maxima of low level cyclonic vorticity correspond to the individual cyclones. Cyclone tracks appear to be influenced by the upper level subtropical jet. the two cyclones which propagate into middle latitudes are accompanied by lower tropospheric warm (cold) air advection ahead of (behind) the system. Both cyclones also exhibit upper tropospheric anticyclonic (cyclonic) vorticity ahead of (behind) the system.
Observation of the airflow over the alps during a foehn event
Authors: Hoinka Klaus P. 
Published: July 2010

AbstractA detailed analysis is presented of the large‐scale, mesoscale and local features of a south‐foehn event in the Alps on 8 November 1982. On this day, with a substantial cross‐mountain flow, instrumented aircraft made programmed flights back and forth across the Alps between southern Germany and northern Italy. Rawinsonde observations were used to complete the data set. A mesoscale double mountain wave with an amplitude of 1 km was found in the upper troposphere. In the mid troposphere above the Inn valley a rather pronounced wave with an amplitude of 2 km and a wavelength of 50 km was analysed. This wave was close to overturning. the foehn turned out to be accompanied by low wave drag at high levels and with strong wave drag at lower levels. Downward southerly (westerly) momentum flux was evaluated to be 0·3 (0·1) Pa. Mountain drag was estimated to be between 1·6 and 6·7 Pa. Light to moderate turbulence was observed immediately to the lee in a low‐level turbulence zone over the region of strong gusty surface winds. Finally, special attention has been devoted to the similarities and possible differences between foehn in the Alps and chinook in the Rocky Mountains.
A primitive equation barotropic instability study of the monsoon onset vortex, 1979
Authors: Mishra S. K. , Patwardhan M. D. , George L. 
Published: July 2010

AbstractA primitive equation barotropic stability analysis of the 700 mb zonal wind profile over the Arabian Sea was performed for each day between 10 and 14 June 1979, during the onset phase of the monsoon. the flow was found to become progressively more unstable with the passage of time. the most unstable inviscid primitive equation mode has an e‐folding time of 3.1 days, a wavelength of 3500 km and a westward phase speed of 1.9ms‐1.The non‐geostrophic effect reduces the growth rate and changes the structure of the unstable mode significantly. It is noticed that when the normalized unstable mode is superposed on the basic state, the total field is closer to the observations. Momentum transports by the primitive equation mode and by the quasi‐geostrophic approximation are in opposite directions in equatorial regions. the energetics of the primitive equation unstable mode are computed and the physical processes responsible for the westward propagation of the wave are identified.
Some physical interpretations of statistically derived coefficients for split‐window corrections to satellite‐derived sea surface temperatures
Authors: McMillin L. M. , Crosby D. S. 
Published: July 2010

AbstractRegression coefficients derived by Llewellyn‐Jones for the split‐ and triple‐window methods of correcting satellite‐derived sea surface temperatures for atmospheric attenuation are examined for consistency with values expected from physical rather than statistical constraints. In this instance, the agreement between physical and statistical approaches is remarkably good. the insight that results from physical considerations illustrates the similarity of coefficients that, from a statistical point of view, appear to be quite different.
A note on the properties of the primitive hydrostatic equations of motion
Authors: Norbury J. , Cullen M. J. P. 
Published: July 2010

AbstractDiscussion of the proper boundary conditions to use in limited area forecasting models requires knowledge of the properties of the governing equations. the theory of Oliger and Sundstrom states that the primitive hydrostatic equations commonly used are not hyperbolic and no local boundary conditions can be chosen. This paper shows their result to be incorrect, the equations are hyperbolic but not all the characteristics involve the time variable. Implications for the boundary conditions are discussed.
Aircraft and dual polarization radar observations of hydrometeors in light stratiform precipitation
Authors: Bader M. J. , Clough S. A. , Cox G. P. 
Published: July 2010

AbstractA case study investigating the relationship of ice phase microphysical structure to differential reflectivity is presented. the distribution of ice crystal types in light precipitation is discussed and shown to agree with a theoretical model of an individual precipitation fallstreak. the particle characteristics were found to reflect sorting by size and type associated with fall through weak wind shear as well as growth in regimes of varying temperature and humidity within the fallstreak.The observed differential reflectivities were compared with the in situ particle measurements and the association of high values with planar crystal structures demonstrated. the particle size distribution was found to have a marked influence on radar returns, particularly through the obscuring effects of large particles of indefinite shape. This effect gave rise to relative variations of differential reflectivity which were found to differ from the predictions of monodisperse models. In particular large dendritic crystals of low density were found in this case to be associated with stronger signatures than denser plate‐like crystals which from theoretical studies might be expected to produce the greatest differential reflectivity. Because of these complicating factors under stratiform conditions it was concluded that differential reflectivity data must be interpreted with considerable caution in the absence of in situ measurements or other supporting data.
The Influence of Diffusional Growth Rates On the Charge Transfer Accompanying Rebounding Collisions Between Ice Crystals and Soft Hailstones
Authors: Baker B. , Baker M. B. , Jayaratne E. R. , Latham J. , Saunders C. P. R. 
Published: July 2010

AbstractLaboratory experiments designed to investigate the charge transfer accompanying rebounding collisions between ice crystals and soft hailstones were performed inside a cold room. They constitute an extension of those conducted with the same apparatus, reported in 1983 by Jayaratne et al. In particular, the range of temperature was extended (to cover −1.5°C to −35°C) and specific tests were performed in an effort to establish relationships between the sign and magnitude of the charging and the growth characteristics of both types of hydrometeor.Significant charging was obtained only when the interacting surfaces were growing by vapour diffusion. the sign of the current, I, flowing to the simulated soft hailstone target in these circumstances was a sensitive function of time, liquid water content, and temperature. the complete set of results is qualitatively consistent with the hypothesis that I is positive if the target surface is growing more rapidly from the vapour than the ice crystals and is negative for the opposite case. In formulating a qualitative model of this hypothesis, account is taken of the contribution made to the diffusional growth of the target by the flux of vapour from droplets freezing onto its surface.Crude calculations designed to assess the implications of these studies with respect to thunderstorm electrification, yield the conclusion that negative soft hailstone charging is likely to predominate over positive in most circumstances.