ISSN:0035-9009    

DOI:10.1002/qj.49709540328

出版商:John Wiley&Sons, Ltd    

年代:1969

数据来源: WILEY

ISSN:0035-9009    

DOI:10.1002/qj.49709540329

出版商:John Wiley&Sons, Ltd    

年代:1969

数据来源: WILEY

ISSN:0035-9009    

DOI:10.1002/qj.49709540330

出版商:John Wiley&Sons, Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractA general formulation of the problem of objective analysis by computer consists of a simple equation in which the value of a meteorological variable at a given grid point is expressed in terms of three components which together include all potential ingredients. Several specialized analysis equations associated with existing schemes are obtained from the general equation, and the relevant methods of specifying weights are outlined. These methods were evaluated by performing a 500 mb height analysis using ‘perfect’ data and the same trial field with each. The best relative results were obtained when weights were determined by solving a system of linear equations involving weight parameters based on the autocovariances of observed minus trial values (residuals). A consideration of conditioning problems suggests that the choice of weight parameter should be appropriate to the manner in which the trial value at the grid point is synthesized. The implications of the investigation are that an optimum method of analysis should take into account data type, quality, distribution, predictability, prediction reliability and a statistical or empirical evaluation of the structure of the meteorological field about every grid po

ISSN:0035-9009    

DOI:10.1002/qj.49709540303

出版商:John Wiley&Sons, Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractZonal and meridional diffusivitiesKxxandKyyhave been found at mid‐latitudes from the spreads of sets of geostrophic trajectories at levels between 700 mb and 30 mb during each season of 1965. Values have been calculated using the relationshipR = e−PTcosqrfor the form of the corresponding Lagrangian autocorrelograms. In addition a similar set of Eulerian data has been analysed to obtain autocorrelograms and by comparison with the trajectory data Eulerian‐Lagrangian scale relationships have been obtained.The results show values ofKxxranging from 0·2.106to about 20.106andKyyfrom 0·2. 106to about 6.106m2sec−1. In both cases the lowest values are found in the summer stratosphere and the highest in the spring stratosphere and in the upper troposphere in winter. Their distributions principally follow that of the wind variances. Integral time scales are mainly between 5 and 30 hours meridionally and 10 and 50 hours zonally and are greatest in the stratosphere and lowest in the mid‐troposphere. The contributions of damping and harmonic effects to these time scales are discussed. Comparison of the Lagrangian and Eulerian time scales indicates a mean value β of about 0·6 for their ratio with the meridional values smaller than the

ISSN:0035-9009    

DOI:10.1002/qj.49709540304

出版商:John Wiley&Sons, Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractThe spheroidal assumption employed by Taylor (1964) has been applied to a theoretical treatment of the deformation and disintegration of charged water drops falling through an electric field of strengthF. Aerodynamic and hydrostatic pressure‐difference terms were incorporated into equilibrium equations from which the fields required to produce instability were determined. Values ofF (Ro/T)1/2required for disintegration were computed as a function of the applied chargeQ, undistorted drop radiusRoand surface tensionT. The predicted values ofF (Ro/T)1/2have been tested experimentally for positively or negatively charged water drops ofRoranging from 0·10 to 0·17 cm falling through horizontal or vertical fields at temperatures varying from + 20 to −18°C. The agreement between theory and experiment was found to be good; the maximum discrepancy of about 3 per cent was obtained with the largest drops utilized and is probably a consequence of the oscillation factor discussed by Ausman and Brook (1967). As predicted, the field required to disintegrate a falling drop was found to be markedly dependent upon the magnitude of the charge that it carried. It is shown that the field,F, required to effect the disintegration of the great majority of charged raindrops falling through the intense electric fields of a thunderstorm can be expressed in electrostatic units to within an accuracy of 2 per cent by the equationF (Ro)1/2= 13·6 – 8Q.The mass loss accompanying the disintegration of falling drops was found to bear a similar relationship to the field strength as was previously observed by Latham (1965) and Matthews (1967). Measurements on suspended drops of water showed that the valués of charge and mass loss,qand δMrespectively, accompanying the disintegration are close to the theoretical maxima. The close parallelism between the experimental curves ofqagainstQand δMagainstQsuggests that instability occurs over a large fraction of the surface area of the lower

ISSN:0035-9009    

DOI:10.1002/qj.49709540305

出版商:John Wiley&Sons, Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractThe problem of determining the distribution of velocity and shear stress in the flow above a surface with an abrupt change in roughness is considered by using the ‘mixing‐length’ theory to relate the shear stress to the velocity profile and solving the resulting system of partial differential equations numerically. The results are compared with those obtained by Panofsky and Townsend (1964) and Taylor (1967), by assuming special forms for the velocity or shear stress pro

ISSN:0035-9009    

DOI:10.1002/qj.49709540306

出版商:John Wiley&Sons, Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractUsing basic data extracted from daily hemispherical cross‐sections constructed at 30°N for March, June, September and December 1958, extensive numerical calculations of mean meridional flow, angular momentum flux and energy flux (i.e. sensible heat, latent heat, potential and kinetic energy) were carried out, and the principal results are reported. Most of the computations are broadly in agreement with earlier estimates; the main differences are uncertainties concerning the energy transpor

ISSN:0035-9009    

DOI:10.1002/qj.49709540307

出版商:John Wiley&Sons, Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractSteady, inviscid, incompressible, two‐dimensional flows of stably stratified fluids over a barrier or barriers are examined theoretically. The density gradient anduρ1/2are assumed to be constant upstream, where ρ is the density anduis the horizontal velocity. Exact solutions of large amplitude waves valid for arbitrary Richardson numbers are obtained for barriers of finite height in a semi‐infinite domain or in a confined channel. These barriers are constructed from vortex pairs and dou

ISSN:0035-9009    

DOI:10.1002/qj.49709540308

出版商:John Wiley&Sons, Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractA definitive statistical relationship is established between tropical cloudiness and rainfall and the semidiurnal solar (S2) atmospheric tide, as manifested in the semi‐diurnal surface pressure variation. Pressure and weather data are used from Batavia (seventy years) and Wake Island (twelve years). TheS2tidal effect is shown to enhance cloudiness and rain near sunrise and sunset, and to suppress them shortly after midday and midnight. The analysis is based on (a) the fact that theS2amplitude varies by 15–20 per cent between months and by more than 100 per cent from day to day and (b) the amplitude of theS2wave as computed from the pressure data at a station is closely related to the 5–6 hourly pressure changes during the periods around 4–5 a.m. to 10 a.m., from 10 a.m. to 4 p.m., etc. The crux of the analysis is the demonstration that days with large 5–6 hourly pressure changes during these periods have large cloudiness changes (in the sense described above) during these same periods relative to days with small 5–6 hourly pressure changes.Possible mechanistic connections betweenS2pressure tendencies and cloud properties are examined. The varying convergence‐divergence field is suggested as the main link. It is shown how the concentration of active cloud updraughts in the Tropics can permit cloudiness to be extremely sensitive to small divergence fields.Finally, large‐scale simultaneous pressure changes over the Pacific Ocean area are shown and related to cloudiness changes. A need for re‐examination of the nature and origins of tropical disturbances is shown to exist, using the concept that possible small (terrestrial or extra‐terrestrial) triggers may set off significant changes in weather both locally and on the synopti

ISSN:0035-9009    

DOI:10.1002/qj.49709540309

出版商:John Wiley&Sons, Ltd    

年代:1969

数据来源: WILEY