ISSN:0035-9009    

DOI:10.1002/qj.49709239402

出版商:John Wiley&Sons, Ltd    

年代:1966

数据来源: WILEY

摘要:

AbstractThe propagation in a shear flow of travelling internal gravity waves of short wavelength is investigated by the W.K.B. approximation. This implies that the Richardson number is large. It is shown that a wave group moves with the local group velocity defined in terms of the dominant wavenumber, the absolute frequency and horizontal components of wavenumber being constant. The wave energy carried by a wave packet varies, being proportional to the frequency relative to a frame moving with the local mean wind. A wave packet, on this approximation, can never pass through a critical level at which its horizontal phase velocity is equal to the mean wind, nor is it reflected there.These results imply restrictions on the propagation of internal gravity waves from the troposphere to the upper atmosphere.

ISSN:0035-9009    

DOI:10.1002/qj.49709239403

出版商:John Wiley&Sons, Ltd    

年代:1966

数据来源: WILEY

摘要:

AbstractThe zonal wind together with the eddy transports of momentum and heat at low and middle latitudes in the stratosphere of the Northern Hemisphere are found to display a two year periodicity which results from a sequence of alternating weak and strong winters, where ‘weak’ and ‘strong’ refer to the intensity of the eddy circulations at middle latitudes. At levels above 30 mb, the modulations in the eddy momentum transports appear to be strong enough to account for the year to year changes in westerly momentum in the tropics.Similarities between the stratospheric oscillation and the biennial pulse in tropospheric data suggest an interrelation between the two phenomena. The two year periodicity may not be a permanent feature of the general circ

ISSN:0035-9009    

DOI:10.1002/qj.49709239404

出版商:John Wiley&Sons, Ltd    

年代:1966

数据来源: WILEY

摘要:

AbstractCollection efficiencies of falling water drops ranging from 1/10 to 1 mm in radius for spores of Lycoperdon (mean radiusr= 2.25 μ), spores of black rust (r= 2.6 μ), and grains of Paper Mulberry pollen (r= 6.4 μ) have been determined. The experimental results are in fair agreement with calculations based on the assumption of potential flow around the larger drops. With both kinds of small spore the collection efficiencies reach maximum values for drops of about 400 μ radius and fall sharply for smaller drops. In this latter regime, where the potential flow solution is inappropriate and the viscous flow solution gives zero values, a sharp fall in collection efficiency is to be expected. Aggregates of two or three spores are collected slightly more efficiently than single spores, but the results show very similar trends in all cases.Some preliminary results have been obtained on the collection of pollen grains by circular, hexagonal and star‐shaped paper discs that simulate snow crystals. The collection efficiencies, as deduced from the numbers of particles caught on their leading faces, are usually<0.05, but the appearance of similar numbers of particles on the trailing faces suggests that particle capture in the wake of the disc is important at these Reynolds numbers of abou

ISSN:0035-9009    

DOI:10.1002/qj.49709239405

出版商:John Wiley&Sons, Ltd    

年代:1966

数据来源: WILEY

摘要:

AbstractThe times of complete melting of small ice spheres in airstreams of controlled temperature, humidity and velocity were measured and compared with the values computed from theory. The theory, which allows for heat transfer to the ice particle by conduction through the air and by condensation upon its surface, agrees quite well with the observations if allowance is made for the heat content of the water retained by the particle during the melting process. The melting times of small ice cones of various shapes did not differ from those of spheres of equivalent volume by more than 10 per cent. It was demonstrated both theoretically and experimentally that an evaporating ice sphere will acquire the same surface temperature as the ice‐coated junction of a thermocouple psychrometer placed in the same airstream provided that the radiation and conduction errors of the latter are rendered negligible by good desig

ISSN:0035-9009    

DOI:10.1002/qj.49709239406

出版商:John Wiley&Sons, Ltd    

年代:1966

数据来源: WILEY

摘要:

AbstractIt is explained that in air descending at speeds of some m sec−1raindrop evaporation must proceed at a large subsaturation. Under some simplifying steady‐state assumptions, the vertical temperature profiles in thunderstorm downdraughts of a range of speeds are estimated, and it is shown that the most favourable conditions for the production of strong draughts are a small raindrop size, and, especially, an intense rainfall rate and a general lapse‐rate close to the dry adiabatic. The two latter conditions are often associated in severe storm situations, and the downdraught then arrives near the ground with a rather low relative humidity, and a temperature little lower than found generally at the same

ISSN:0035-9009    

DOI:10.1002/qj.49709239407

出版商:John Wiley&Sons, Ltd    

年代:1966

数据来源: WILEY

摘要:

AbstractEnergy dissipation rates and the eddy fluxes of sensible heat, momentum, and total kinetic energy have been measured above a non‐homogeneous surface. Calculations were made from simultaneous observations of fluctuations in air temperature and the orthogonal components of wind velocity at heights of 16 m and 40 m. In all thermal stratifications, dissipation rates given by the Kolmogoroff structure function are in close agreement with direct measurements of the energy extracted from the mean flow. During stable stratification, energy losses due to work done against gravity and to the divergence of the vertical flux of turbulent kinetic energy are nearly an order of magnitude smaller than the dissipation. In unstable stratification, energy losses due to the flux divergence are of the same order as the dissipation and are approximately three times larger than the energy produced by buoyancy. Estimates of the vertical heat flux from the Obukhov structure function compare favourably with directly‐measured fluxes if the constant in the structure function is assigned a value of 0.7 in lapse conditions and a value of 1.6 in inversion conditions. The measurements also show that the ratio of the diffusivities of heat and momentum at a height of 16 m is significantly greater than unity in unstable stratification and significantly less than unity in stable stratification. Finally, the new measurements of dissipation rate are shown to be consistent with values obtained in previous stud

ISSN:0035-9009    

DOI:10.1002/qj.49709239408

出版商:John Wiley&Sons, Ltd    

年代:1966

数据来源: WILEY

摘要:

AbstractReynolds' equations are generally valid only when the bar operator represents an ensemble average. Such averages are rarely calculated in practice, the usual approach (especially in micrometeorology) being to calculate a time average instead. When conditions are at all unsteady, this practice necessitates consideration of additional terms in the expression for the Reynolds flux. It is shown, with the aid of a series of rapid‐response measurements of wind and temperature, that these terms are not necessarily negligible and that under unsteady conditions the complete Reynolds flux expression may differ considerably from the quantity generally computed; also, the vertical gradients of the two quantities will differ. A quantitative criterion of steadiness is proposed and is shown to be highly correlated with the difference between the complete Reynolds flux and the quantity usually calculate

ISSN:0035-9009    

DOI:10.1002/qj.49709239409

出版商:John Wiley&Sons, Ltd    

年代:1966

数据来源: WILEY

摘要:

AbstractAlbedo data are presented from ground and airborne measurements over different types of cover in Southern England. Summer values show a range of at least 10 per cent (15 per cent for heath, 16 to 18 for woodland and built‐up areas and 24 to 25 per cent for green cereals and grass). These and published albedos are used to prepare a map of summer albedo over the country based on the vegetation maps in The Atlas of Britai

ISSN:0035-9009    

DOI:10.1002/qj.49709239410

出版商:John Wiley&Sons, Ltd    

年代:1966

数据来源: WILEY

摘要:

AbstractObservations of the total ozone at Halley Bay (75°S) during the I.G.Y. showed that the annual variation there was very different from that found at a similar northern latitude. Later observations now available show similar characteristics. Further, recent measurements at the South Pole and at Byrd (80°S) give similar results to those at Halley Bay, indicating that this type of annual variation is probably characteristic of Antarctica generall

ISSN:0035-9009    

DOI:10.1002/qj.49709239411

出版商:John Wiley&Sons, Ltd    

年代:1966

数据来源: WILEY