摘要:

AbstractThe problem of evaporation from large expanses of water is of fundamental importance. The evaporation from oceans is of importance in studying the amount of water vapour which an air mass receives while flowing over the ocean. Among recent investigations on the problem of evaporation may be mentioned in particular those of Sverdrup (1936), Millar (1937), and Montgomery (1940). But the final conclusive results of these authors differ very much from each other. For instance, Sverdrup (1937–8) concludes that the evaporation from a hydrodynamically rough surface must be twice as great as that from a smooth surface, while Montgomery infers it to be about the same in both cases. The question is reconsidered below, the work of these authors being followed to a certain extent, but not entirely. The differences are emphasised wherever necessary. The present investigation leads to the result that the evaporation from a hydrodynamically rough surface must be about four times as great as that to be expected from a smooth surface of wate

ISSN:0035-9009    

DOI:10.1002/qj.49707431902

出版商:John Wiley&Sons, Ltd    

年代:1948

数据来源: WILEY

摘要:

AbstractThe details of the processes by which heat is transported through the lower atmosphere are, for the most part, still obscure although our knowledge of typical temperature distributions near the ground is now well founded, thanks chiefly to the researches of Johnson (1929), Best (1935), Flower (1936) and Johnson and Heywood (1938). These investigations establish in considerable detail the principal features of the mean temperature field from 2·5 cm. to 87 m., so that the data for the elucidation of the problems of heat transfer are undeniably available, but the complexity of the situation, depending as it must upon the joint effects of radiation, conduction and convection, is such that there is little hope that a comprehensive mathematical theory will be evolved for some time yet.The present paper is an attempt to clarify certain aspects of the problem, and in particular to analyse the general nature of the flux of heat through the lower atmosphere on a clear day in summer. The conclusion is reached that to explain the type of heat flow which prevails in these conditions necessitates the consideration of the nature of the vertical currents due to buoyancy and their effect on the virtual coefficient of conduction, and for this purpose a theoretical treatment is proposed which differs in many ways from those previously advanced

ISSN:0035-9009    

DOI:10.1002/qj.49707431903

出版商:John Wiley&Sons, Ltd    

年代:1948

数据来源: WILEY

摘要:

AbstractThe thundery conditions which often develop in Egypt, Palestine and Syria, during the autumn, have been further investigated. They have been found to occur when the Sudan monsoon low intensifies towards the north and supplies the eastern Mediterranean with a warm south‐easterly current.In a great many cases, shallow depressions form over the southeastern Mediterranean, or the adjacent land areas, as a result of the meeting of the above current with the relatively cold northeasterly air of anti‐cyclonic distribution in Asia Minor. In a few cases they form over the western Desert in a manner resembling the formation of khamsin depressions. After being fully developed, these depressions move eastwards or north‐eastwards, while the inflow of the cold air in the rear gives thundery showers. Such thunderstorms are specially marked over the sea, Palestine and Syria.Over Egypt, however, high‐level instability frequently exists between the warm current and the cool air advancing above. Owing to the stability of the surface layers, this high‐level instability cannot pass into the thunderstorm stage without sufficient convergence of damp air. With a high degree of latent instability severe thunderstorms are then

ISSN:0035-9009    

DOI:10.1002/qj.49707431904

出版商:John Wiley&Sons, Ltd    

年代:1948

数据来源: WILEY

摘要:

AbstractThe observation of the forms of high clouds suggests that ice clouds usually arise at humidities representing saturation with respect to water and therefore at a considerable supersaturation with respect to ice, which in combination with a sparsity of effective nuclei leads to the rapid growth and high falling‐speed of the few ice particles. Recent theoretical and experimental investigations, principally by German meteorologists, fully support this view, and a brief account of their work is given in Part I of the present paper. In Part II it is shown how the new views provide an explanation of the distinctive fibrous structures of ice‐clouds, and give additional insight into the nature of cirrus uncinus and zig‐zags, of mixed clouds and of virga or fallstreifen, and also into the processes which bring about the decay of cumulonimbus and the formation of mammato‐clouds. Possible practical applications include that of dispersing natural clouds and the production of rain by the use of artificial ice

ISSN:0035-9009    

DOI:10.1002/qj.49707431905

出版商:John Wiley&Sons, Ltd    

年代:1948

数据来源: WILEY

摘要:

AbstractThe depressions of middle and high latitudes cause the raising of large masses of air from low to high levels in the troposphere.As the air is lifted it soon becomes cooled below its saturation temperature and its surplus water vapour condenses into cloud particles and later into rain or other forms of precipitation.Thus the rate of rainfall is a rough measure of the rate of lifting, or the upward velocity, of the air above.It is shown here how this measure may be made more precise when it is certain that the lifting process is on a large scale and comparatively uniform and not influenced by local instability effects.Examples of the application of the method are given, and it appears that upward velocities of from 10 to 20 cm. per second (i.e.9 to 17 km, per day), are usual in the active depressions often experienced over the North Atlantic.

ISSN:0035-9009    

DOI:10.1002/qj.49707431906

出版商:John Wiley&Sons, Ltd    

年代:1948

数据来源: WILEY

ISSN:0035-9009    

DOI:10.1002/qj.49707431907

出版商:John Wiley&Sons, Ltd    

年代:1948

数据来源: WILEY

摘要:

AbstractA result from a previous paper (Priestley 1947) indicates the existence of a broad upper limit to the size of pressure systems, and a lower limit to the distance separating the centres of two significant closed pressure systems. The pressure field has thus an inherent scale of pattern which varies with latitude, imposed by the essential geometry and dynamics of atmospheric flow. Orders of magnitude deduced theoretically agree well with experience. The implications contribute to an understanding of the mechanism of the mean global circulation.

ISSN:0035-9009    

DOI:10.1002/qj.49707431908

出版商:John Wiley&Sons, Ltd    

年代:1948

数据来源: WILEY

ISSN:0035-9009    

DOI:10.1002/qj.49707431909

出版商:John Wiley&Sons, Ltd    

年代:1948

数据来源: WILEY

ISSN:0035-9009    

DOI:10.1002/qj.49707431910

出版商:John Wiley&Sons, Ltd    

年代:1948

数据来源: WILEY

摘要:

AbstractThe diurnal and semi‐diurnal waves of barometric pressure are obtained for individual days. The diurnal wave, with a mean amplitude of from 0·6 to 0·8 mb., shows a standard departure from the mean of 0·25 mb., and, in consequence is sometimes absent. The semi‐diurnal wave, with a mean amplitude of 1·0 mb., shows a standard departure of only 0·1 mb., and the phase is very steady. The reality of these variations is supported by correlation between stations and with diurnal variations of tem

ISSN:0035-9009    

DOI:10.1002/qj.49707431911

出版商:John Wiley&Sons, Ltd    

年代:1948

数据来源: WILEY