ISSN:0035-9009    

DOI:10.1002/qj.49707833502

出版商:John Wiley&Sons, Ltd    

年代:1952

数据来源: WILEY

摘要:

AbstractIt is shown theoretically that the rate of nucleation of the ice phase in supercooled water changes very rapidly with temperature in the neighbourhood of −40°C. Thus, in chilling a supercooled water cloud below this temperature one would expect to observe a rapid increase in the number of ice crystals which appear as the temperature falls. This is verified by observations made in a cold chamber. The different critical temperatures for the spontaneous appearance of ice crystals quoted by Schaefer (−39°) and the Oxford workers (−41°C) probably arise as the result of differences in the experimental conditions. It is tentatively suggested that the parts of mother‐of‐pearl clouds showing iridescence at temperatures around −80°C consist of spheres of ‘glassy’ ice, which may eventually crystallize spontaneously to form ice crystals towards the leeward

ISSN:0035-9009    

DOI:10.1002/qj.49707833503

出版商:John Wiley&Sons, Ltd    

年代:1952

数据来源: WILEY

摘要:

AbstractEquations are developed to represent the rate of change of the number of drops of a given size in a cloud owing to condensation and to coalescence respectively. Numerical computation from these equations shows that condensation has a much greater effect than coalescence on drop‐size distribution in clouds with small average drop size, with small liquid‐water content or with a large degree of super‐saturation.With the assumption that drop‐size distribution in a cloud is governed by rate of condensation on the drops in the cloud and rate of turbulent diffusion of the drops out of the cloud it is then shown that the fractional volume of water comprised by drops smaller than a specified size is expressible in terms of an Incomplete Gamma function. In this Incomplete Gamma function the argument is 1·5 and the upper limit to the integral varies as the square of the drop size and is also proportional to a quantity which depends upon the degree of turbulence and upon parameters connected with the rate of condensation. It is shown that this theoretical formula approximates closely to a simpler formula already established empirically and that reasonable values for the coefficient of turbulence and the condensation parameters lead to a mean drop size which agrees closely with measure

ISSN:0035-9009    

DOI:10.1002/qj.49707833504

出版商:John Wiley&Sons, Ltd    

年代:1952

数据来源: WILEY

摘要:

AbstractThe theory of the formation of rain by coalescence leads logically to the suggestion that, if water drops of suitable size are sprayed into the base of a convective cloud, the drops will ascend in the upward air current, will grow by coalescence with the cloud droplets and may ultimately fall out as rain. Calculations show that under appropriate conditions the drops could attain a diameter greater than 1 mm and emerge from the base of the cloud from 20 to 60 min after water had been sprayed into it.Eleven experiments have been carried out to test the possibility of the method. In 10 cases, distinct changes occurred following the introduction of a water spray into the selected cloud. In 4 of these, virga fell from the cloud and it dissipated soon afterward. In 4 cases, rain or hail appeared shortly after spraying. On only one occasion were no results observed.The results suggest that the method might be useful for the artificial stimulation of rainfall, but further experiments are required to fully establish the mechanism.

ISSN:0035-9009    

DOI:10.1002/qj.49707833505

出版商:John Wiley&Sons, Ltd    

年代:1952

数据来源: WILEY

摘要:

AbstractA new method of measurement of the liquid‐water content of clouds is described. It depends on the change of resistance of a paper tape on being moistened by cloud droplets which impinge directly on it. A continuous and permanent record of the liquid water can be obtained, and variations over distances of a few hundred feet can be detected. Measurements have been made using the technique on a number of cumulus and stratocumulus clouds, some characteristics of which are describe

ISSN:0035-9009    

DOI:10.1002/qj.49707833506

出版商:John Wiley&Sons, Ltd    

年代:1952

数据来源: WILEY

摘要:

AbstractThe surface wind in the Straits of Gibraltar is determined by the interplay of its inclination to blow towards the end where surface pressure is lowest when the air is stable and its tendency to follow the upper wind if convection is active. The importance of cold pools of air lying below mountain‐top level is discussed and various kinds of wind reversal are describe

ISSN:0035-9009    

DOI:10.1002/qj.49707833507

出版商:John Wiley&Sons, Ltd    

年代:1952

数据来源: WILEY

摘要:

AbstractA marked seasonal variation of the poleward angular‐momentum flux for the northern hemisphere in the vicinity of 30°N. latitude is obtained from an analysis of upper‐wind soundings for a period of one year. The angular‐momentum flux appears to be about twice as great during the winter as during the summer. Indications of a mean meridional circulation of the strength and character necessary to provide a substantial flux of angular momentum are lacking. It is suggested that the horizontal eddy flux of angular momentum across 30°N. latitude is sufficient to account for the drain of this momentum in middle la

ISSN:0035-9009    

DOI:10.1002/qj.49707833508

出版商:John Wiley&Sons, Ltd    

年代:1952

数据来源: WILEY

摘要:

AbstractDaylight received on a horizontal surface has been measured for fourteen years using a Burt vacuum sodium cell and Cambridge thread‐recorder galvanometer. Mean monthly values of daily maxima, in kilolux, are tabulated, also mean monthly values of illumination in kilolux hours. These are compared with similar measurements at Kew in 1947 and 1948, obtained using a selenium cell. The kilolux hours for each month are shown as a percentage of individual years, with mean values for fourteen years and percentage range for variation. Annual totals were 108, 124 and 122 megalux hours for 1947, 1948 and 1949 respectively with 116 as the mean of the whole series. Between these and sunshine or rainfall there is no simple relation. Cloudless days are not the brightest owing to downward reflection from clouds. Darkest days in each month commonly show 17 to 40 per cent as many kilolux hours as do brightest, though smoke pollution may reduce illumination to 5 per cen

ISSN:0035-9009    

DOI:10.1002/qj.49707833509

出版商:John Wiley&Sons, Ltd    

年代:1952

数据来源: WILEY

摘要:

AbstractThis paper describes the role of sonic disturbances in redistributing the mass of the atmosphere when heating or cooling is applied to a part of it. It is shown that the effect, for meteorological purposes, of heating is a local reduction of density and surface pressure. The pressure field thus set up causes an advective disturbance which later modifies the field by transport of mass with the wind.It is concluded that no disturbance of meteorological significance ever travels from one place to another otherwise than by advection.

ISSN:0035-9009    

DOI:10.1002/qj.49707833510

出版商:John Wiley&Sons, Ltd    

年代:1952

数据来源: WILEY

摘要:

AbstractThis study is restricted to days with even pressure distribution, and without strong winds that would interfere with the sea breeze. The greatest frequency of such a sea breeze occurs in May, June and October, which are the months of low frequency of the Etesians.The diurnal march of vapour pressure at Athens is clearly double in all months and the year as a whole. However, on days with uninterrupted sea breeze, mainly from May to October, three pairs of extremes characterize the variation, there being two secondary maxima and two secondary minima in the forenoon. The arrival of the moist sea breeze overcompensates the normal decrease of vapour pressure in the morning.

ISSN:0035-9009    

DOI:10.1002/qj.49707833511

出版商:John Wiley&Sons, Ltd    

年代:1952

数据来源: WILEY