摘要:

AbstractRecently published measurements of shadow‐band patterns produced by star‐light at ground level are analysed using the theory of wave‐propagation in a turbulent medium. The measured spatial and time spectra of the patterns can be described quantitatively by assuming that the optical inhomogeneities are produced by turbulent mixing in the earth's boundary‐layer and in shallow layers at heights around 8 km. Characteristics of the assumed turbulence in the upper air are estimated to be: mean height 8 km, layer depth 90–200 m, r.m.s. velocity fluctuation in wind direction 1·5‐2·0 m sec−1, r.m.s. temperature fl

ISSN:0035-9009    

DOI:10.1002/qj.49709138702

出版商:John Wiley&Sons, Ltd    

年代:1965

数据来源: WILEY

摘要:

AbstractThe Eulerian and Lagrangian autocorrelations and energy spectra of the large‐scale turbulent motion in the atmosphere are computed and analysed. It is found that the distributions of the Eulerian and Lagrangian autocorrelations of the zonal velocities show the characteristic of an exponentially decreasing function, whereas those of the meridional velocities exhibit the behaviour of a sinusoidal function with a damping amplitude. The energy spectra appear to be proportional to the minus second power of the frequency in the high frequencies.Analyses are also made of the energy spectra, autocorrelations, and the Eulerian‐Lagrangian time scale transformation in a planetary wave model. The ratio of the Eulerian and Lagrangian frequencies for the large‐scale atmospheric turbulence is found to be a function of the mean zonal velocity, latitude, and the angular wave number of the planetary wave. Comparisons are made of the energy spectra and autocorrelations derived from the planetary wave model and those found from observa

ISSN:0035-9009    

DOI:10.1002/qj.49709138703

出版商:John Wiley&Sons, Ltd    

年代:1965

数据来源: WILEY

摘要:

AbstractThe vertical transfer of moisture is examined under conditions where the Richardson number varies from − 2.5 to + 2.9. The use of a non‐dimensional evaporative flux, similar to Priestley's (1959) non‐dimensional sensible heat flux, and extensive data from the Davis lysimeter field show a smooth transition from forced to free convection. An equation for this transitional regime of mixed convection is derived by dimensional analysis and fitted to the data for different Richardson number ranges. A free convection interpretation of the data for −2.5

ISSN:0035-9009    

DOI:10.1002/qj.49709138704

出版商:John Wiley&Sons, Ltd    

年代:1965

数据来源: WILEY

摘要:

AbstractUsing a ‘variance function’ to specify the variance retained by a time series smoothed via running means, it is shown that the rate of turbulence dissipation can be computed from an Eulerian wind record supplied by a single, 3‐cup anemometer through the relation ϵ =(A)[( ‐)/(Tk2/3‐ Tj2/3)]3/2Here A ≈︁ 3.3 derives from the Kolmogoroff law, Ū is the mean flow, and the numerator of the bracketed term represents the additional reduction in variance effected by increasing the averaging interval fromTjtoTk. Preliminary verifications of the relation are presented, and an experimental programme designed to use the met

ISSN:0035-9009    

DOI:10.1002/qj.49709138705

出版商:John Wiley&Sons, Ltd    

年代:1965

数据来源: WILEY

摘要:

AbstractA technique is described for evaluating directly from a single streak photograph the impact parameter for a collision between two falling water drops of similar size. Collision results from one member of a pair of drops being accelerated in the wake of the other. An analysis of many such photographs allows the collection efficiency to be determined. No coalescences were observed between droplets of radiusR<35 μ. Droplets of 40 μ

ISSN:0035-9009    

DOI:10.1002/qj.49709138706

出版商:John Wiley&Sons, Ltd    

年代:1965

数据来源: WILEY

摘要:

AbstractSystematic observations were made of hydrometeor charges associated with thunderstorms at Flagstaff, Arizona. The measurements were made from a light aircraft by the standard induced‐charge method, in and below clouds which were entirely supercooled. The aircraft would spiral within the central upcurrent up into the cloud and later spiral down through the precipitation shafts. From these limited cases, a rather consistent picture emerged: (a) generally, charges on graupel and hail within the supercooled clouds were positive (measurements made as high as the −17.5°C level), (b) below the cloud at the + 2° to + 8°C level, just where the melting of the hydrometeors was apparently complete, the hydrometeors became abruptly negative, (c) at still lower, warmer levels the charge magnitudes were consistently smaller, with both signs represented but predominantly negative. The data suggest that a strong hydrometeor charging mechanism is associated with the melting of ice hydrometeors outside the cloud. The maximum charge magnitudes appeared comparable to the amounts which would be limited by breakdown gradients at the hydrometeor s

ISSN:0035-9009    

DOI:10.1002/qj.49709138707

出版商:John Wiley&Sons, Ltd    

年代:1965

数据来源: WILEY

摘要:

AbstractA brief laboratory investigation was initiated to try to duplicate a phenomenon which had been repeatedly observed in certain flight measurements during the Flagstaff cumulus studies: the apparent strong negative charging of ice hydrometeors in the final stage of melting during their fall outside of the cloud. Sample ice structures of 1 cm3from distilled water were melted in an 8 m sec−1air stream at ambient temperatures. Regardless of the technique of measurement used (current into the sample, charge into the sample, or charge into an open Faraday cage around the sample), certain features were observed consistently: (a) a positive charge was acquired by the sample, (b) the magnitude of the charge was of the order of 30 picocoulombs (0.1 esu), and (c) the acquisition of charge occurred primarily during the later portion of the melting process. Generally similar but more erratic results were obtained with actual hail samples.The sign of the charging was opposite to that observed in the flight measurements, and the magnitude of the charging was far less, but the correlation of the charging with the final stage of melting agreed with the results of the flight tests. Careful laboratory tests previously reported by Dinger and Gunn also showed positive charging during melting, and the charging correlated with the amount of dissolved gas and hence bubbles. It is felt that the charging effect is real and is probably primarily associated with effects from bubbles during melting, and that the disagreement in sign and magnitude between the laboratory and flight measurements may be attributable to the large differences in ambient conditions and differences in the physical and chemical properties of the hydrometeor

ISSN:0035-9009    

DOI:10.1002/qj.49709138708

出版商:John Wiley&Sons, Ltd    

年代:1965

数据来源: WILEY

摘要:

AbstractBased on the evaluation of atmospheric electricity data recorded synoptically over a period of several years in a high‐mountain area between 600 and 3,000 metres above sea‐level, observations of the behaviour of several atmospheric electricity parameters are briefly presented. Besides providing information on charge separation occurring during drifting snow and on cloud charges, the results show the fundamental importance, with respect to atmospheric electricity phenomena, of the melting zone of falling precipitation and of the intensity of atmospheric turbulence and its dependence on altitude. A generally applicable mathematical formulation is given for the relation between the potential gradient and the precipitation current density. This is valid for both low and high altitudes above sea‐level and takes the differences between different types of precipitation into ac

ISSN:0035-9009    

DOI:10.1002/qj.49709138709

出版商:John Wiley&Sons, Ltd    

年代:1965

数据来源: WILEY

摘要:

AbstractMeasurements have been made of the activity collected by a stream of distilled‐water droplets falling through an atmosphere saturated with tritiated water vapour. The results, combined with those of Friedmanet al.(1962), confirm theoretical predictions of the rate of exchange between droplets of radius 40‐1500 microns and the surrounding vap

ISSN:0035-9009    

DOI:10.1002/qj.49709138710

出版商:John Wiley&Sons, Ltd    

年代:1965

数据来源: WILEY

摘要:

AbstractWhen 633 supercooled drops of mean diameter 1.3 mm were nucleated with ice crystals at −1°C and then frozen in air at −15°C the 91 measurable charges on the residues of the 118 drops which broke ranged from −17 × 10−3to + 25 × 10−3e.s.u. Spicules were always formed before the drops broke, and in 48 cases the break was across the spicule stem. The breaking spicules containing liquid water resulted mainly in negatively charged residues. Solid spicules usually left positively charged residues. When these results are combined with those of Evans and Hutchinson (1963) the average charge for liquid spicule residues is − 1.4 ± 0.9 × 10−3e.s.u. (49 drops) and for solid spicules + 3.4 ± 2.2 × 10−3e.s.u. (25 drops). Other reported observations are also discussed. The magnitudes of the charges are rather high to be explained entirely in terms of the temperature‐gradient theory of Latham and Mason. There appears to be considerable evidence for a charge separation across the boundary between the freezing water and the ice, water being

ISSN:0035-9009    

DOI:10.1002/qj.49709138711

出版商:John Wiley&Sons, Ltd    

年代:1965

数据来源: WILEY