ISSN:0035-9009    

DOI:10.1002/qj.49709339702

出版商:John Wiley&Sons, Ltd    

年代:1967

数据来源: WILEY

摘要:

AbstractDuring the summer of 1963, sonic anemometers were mounted at 46, 137, 229 and 320 metres on a 430 metre tower to measure turbulent fluctuations in the vertical velocity component. Mean horizontal wind speeds and temperatures were measured at 12 levels on the tower.Characteristic behaviour of power spectra for four typical stability conditions are described. Evidence of an inertial subrange is found at all levels regardless of stability. Analysis of the rate of dissipation, ϵ, indicates that there is no simple relationship which can describe its behaviour with height for all conditions. Its behaviour is shown to change with thermal stratification; ϵ remains relatively constant with height during well‐established convection but decreases rapidly above 46 m when the temperature gradient is stable. It is also shown that ϵ is roughly proportional to the product of the third power of the standard deviation of the vertical velocity component and the wave number of its logarithmic spectral peak.The data from the sonic anemometers provide some additional information on the structure of convection during very unstable lapse conditions. Analyses of coherence between successive levels indicate the presence of a second generation of convective elements above the plume convection generally observed near the ground. The transition layer is estimated to be in the vicinity of 100 m. The scale of turbulence for the top three levels shows an initial increase with increasing instability followed by a decrease. It is conjectured that this decrease is a consequence of the fact that the second‐generation convective elements move faster than the wind speeds indicated at the level of instrumen

ISSN:0035-9009    

DOI:10.1002/qj.49709339703

出版商:John Wiley&Sons, Ltd    

年代:1967

数据来源: WILEY

摘要:

AbstractPhotographic and radiometric records of the summit areas of severe storms in Oklahoma obtained from a U‐2 aircraft flying at an altitude of 65,000 ft (20 Km) are combined with relevant synoptic data to make some tentative deductions on the nature of the flow and temperature fields in the outflow regions of the small fraction of giant storm cells which appear to have attained some form of quasi‐steady state.The summit area of a giant cell sometimes appears to consist of a rather smooth ‘gasometer‐shaped’ dome 5–8 nautical miles (10–15 Km) in diameter and reaching up to 20,000 ft (6 Km) above its environmental tropopause. It is suggested this dome consists mainly of air which has risen nearly adiabatically from the surface layers (after Ludlam 1963) contained within a rather thin shell of very stable air in which there is mixing between updraught air and environmental (stratospheric) air.A general description of the distribution and heights of storm tops along a developed squall‐lin

ISSN:0035-9009    

DOI:10.1002/qj.49709339704

出版商:John Wiley&Sons, Ltd    

年代:1967

数据来源: WILEY

摘要:

AbstractLong‐term global integrations of the primitive equations for the free‐surface model are performed using spherical polar co‐ordinates. Two methods are used to overcome the computational drawback of excessive resolution near the poles. In the first, time‐steps vary latitudinally on a grid with constant angular increments. Stable integrations result, in which the evolutions closely match (save for phase‐truncation due to divergence) those of the analytic solution of the non‐divergent vorticity equation for initial data in which non‐linear interactions vanish. In the second set of integrations zonal resolution varies latitudinally, and the resulting differential phase‐truncation causes spurious interactions which lead to rapid departure from the analytic solution. In both cases finite difference approximations are used which preserve domain sums of mass and of total energy (kinetic plus potential), in analogy with properties of the continuous equations. The space‐differencing method, together with the time‐smoothing inherent in the variable time‐step scheme, may have helped to suppress non‐linear instability in the fi

ISSN:0035-9009    

DOI:10.1002/qj.49709339705

出版商:John Wiley&Sons, Ltd    

年代:1967

数据来源: WILEY

摘要:

AbstractAn experimental study of the structure of thermal convection in the lower atmosphere is presented. The measurements were undertaken with the primary purpose of comparing the statistics of convective motion occurring in the lower atmosphere under conditions of light winds and strong surface heating with the laboratory heated plate results of Townsend and also with the predictions of the similarity theory of free convection. Temperature and vertical velocity fluctuations were measured above a desert dry lake bed in Southern California using a light aircraft as an instrument platform. Modern data acquisition methods were used which allowed high speed data sampling and rapid computer processing of several million data points. Negative Richardson numbers at 1·5 m of the order of 2 or more were typical of the midday hours. The temperature traces obtained during horizontal aircraft traverses had the typical intermittent structure previously noted both in the atmosphere and in the laboratory by other investigators. Individual warm pulses often had an asymmetric appearance in that the upwind edge tended to be the warmest. This was noted to hold even for the lightest wind conditions included in these data (1 ms−1at 4 m). Although the observed intermittency of the temperature field agreed qualitatively with Townsend's description of the laboratory case, the variation with height of the r.m.s. temperature and vertical velocity fluctuations agreed with the predictions of the similarity theory of free convection. It is concluded that the light wind case in the atmosphere differs considerably from the laboratory case with no mean motion. Since winds appreciably lighter than those occurring during this study are quite rare for lapse conditions in the atmosphere, it is suggested that there may always be a fundamental difference between atmospheric measurements and those made for the classical heated plate experiments. These data are also used to construct a preliminary kinetic energy budget for various heights above the lake bed. The results indicate that the flux divergence of turbulent kinetic energy is a large term in the budget under the conditions of these measuremen

ISSN:0035-9009    

DOI:10.1002/qj.49709339706

出版商:John Wiley&Sons, Ltd    

年代:1967

数据来源: WILEY

摘要:

AbstractIn this note three‐day mean temperature values observed at Colaba (Bombay) during the years 1871 to 1960 have been examined by means of contingency tables for evidence of any pattern of persistence during the South‐West Monsoon. It appears that the tendency for the existing temperature character to persist from one triad to the next at least is strong during the entire monsoon, being strongest in the month of August, when it may persist over a period of 4 triads or

ISSN:0035-9009    

DOI:10.1002/qj.49709339707

出版商:John Wiley&Sons, Ltd    

年代:1967

数据来源: WILEY

摘要:

AbstractThe relationship between vertical wind shear and the vertical extent of convective clouds is examined. In order to take into consideration the movement of the cloud, a ‘Relative Top Shear’ (RTS) is defined. Radar data and upper winds at some Indian stations in different seasons have been studied and a comparison made between RTS at different levels and the maximum tops of convective clouds. The results show that deep convective cloud was confined to layers in which RTS did not exceed 10 kt

ISSN:0035-9009    

DOI:10.1002/qj.49709339708

出版商:John Wiley&Sons, Ltd    

年代:1967

数据来源: WILEY

摘要:

AbstractIt is shown that solutions of Laplace's tidal equations in the presence of a non‐zero zonal flow may be obtained from the usual solutions for perturbations about a state of rest relative to the Earth, provided one uses an appropriate modification of the equivalent depth. Typically the modification leads one to the solutions which for zero zonal flow would be applicable to negative depth

ISSN:0035-9009    

DOI:10.1002/qj.49709339709

出版商:John Wiley&Sons, Ltd    

年代:1967

数据来源: WILEY

摘要:

AbstractThe equation for radiative flux divergence in a stratified atmosphere is derived from first principles. Cooling to space, and internal transfer, are seen as distinct physical processes which merit independent treatment.

ISSN:0035-9009    

DOI:10.1002/qj.49709339710

出版商:John Wiley&Sons, Ltd    

年代:1967

数据来源: WILEY

摘要:

AbstractThe numerous stations which operated in Antarctica during the International Geophysical Year allow a more detailed study of the local distribution and of the displacements of pressure variations. From six‐hourly pressure data the times of occurrence of identifiable extremes have been determined. They are mostly later at the more westerly stations. For 15 months and seven stations, cross‐correlations of six‐hourly pressure values have been calculated for lags of multiples of six hours between 60 and — 60 hours. The correlations are in most cases highest for pressures at the eastern before the western station. The same result is found if six‐hourly and twenty‐four hourly pressure changes at different stations are correlated instead of the pressures themselves. No correlations of the same size occur if between Little America and Wilkes pressures and pressure changes at a station are correlated with later ones at a more easterly location. The existence and importance of Simpson's ‘antarctic pressure waves’ is

ISSN:0035-9009    

DOI:10.1002/qj.49709339711

出版商:John Wiley&Sons, Ltd    

年代:1967

数据来源: WILEY