摘要:

AbstractPhotographs of thin sections through five giant hailstones are presented to portray their bubble and crystal structures. These are interpreted to show that the hailstones grew as three‐dimensional arrays of more or less completely frozen lobes, sometimes but not always separated by regions of spongy ice characterized by radial lines of bubbles.Some lobes contained regularly spaced hyperfine growth layers consisting of series of concentric bubble fronts a few hundred microns apart. These layers are interpreted as being due to fluctuations in growth rate associated with the tumbling of the hailstones.The growing surfaces of the lobes were strongly convex outward. This caused successive growth layers to become convoluted or scalloped. When the surface of a whole hailstone was viewed it sometimes created the false impression that the stone was an aggregate of much smaller hailstones.The presence of surface knobs associated with the lobes significantly enhances the efficiency of heat loss from the hailstone surface. Such an effect is important in that it reduces the proportion of unfrozen water incorporated within a rapidly growing hailstone. There is even some evidence that a giant 8 cm diameter hailstone can grow in this way without becoming appreciably spong

ISSN:0035-9009    

DOI:10.1002/qj.49709239102

出版商:John Wiley&Sons, Ltd    

年代:1966

数据来源: WILEY

摘要:

AbstractObservations of frontal precipitation using a vertically‐looking 3.2 cm pulsed Doppler radar have been analysed to indicate the raindrop‐size distributions present below the melting band. The variations of size distribution with rainfall rate and with height are discussed. The distributions at 750 m above ground show both fewer small drops and fewer large drops than the corresponding Marshall and Palmer (1948) exponential distributions. At greater heights there are more small drops but even fewer large drops. The changes of rain‐flux and drop‐size distribution with height provide evidence in support of raindrop coalescence but, in general, indicate the absence of pronounced accretion or evaporation. Experimental relations between equivalent reflectivity factorZeand rainfall rateRhave been derived for two heights; extrapolated to ground level the relation isZe= 285R1.30for continuous frontal rains of 0.1 to 5.0 mm hr−1at Pershore. Instances of vertical air motion due to waves induced by hills have been

ISSN:0035-9009    

DOI:10.1002/qj.49709239103

出版商:John Wiley&Sons, Ltd    

年代:1966

数据来源: WILEY

摘要:

AbstractA method of measuring convergence in precipitation using a Doppler radar is described. A case study illustrates the results obtainable. The presence of a ‘wind front’ (sloping shear zone), which could not be related to any feature on the synoptic scale, was revealed (Fig. 6). Layers of convergence and divergence, particularly in association with a frontal inversion, were identified (Fig. 7). Convergence below the front was largely compensated by a pronounced divergence (D ∼ 50 × 10−5sec−1) immediately above the front. The computed vertical velocities (Fig. 9) showed ascent of the order of 10−2mb sec−1during the rain.Although measurements were made over an area of less than 300 km2, the evidence suggests that the variations of convergence were not purely local, but were a consequence of an organized dynamical system on a scale comparable with other feat

ISSN:0035-9009    

DOI:10.1002/qj.49709239104

出版商:John Wiley&Sons, Ltd    

年代:1966

数据来源: WILEY

摘要:

AbstractA series of high resolution robin falling‐sphere soundings covering the altitude range from 70 to 27 km have been examined in detail. Small‐scale wind variations with height are evident throughout. From profiles of the zonal wind components the apparent amplitudes and half‐wavelengths have been tabulated and summarized for 19 cases, divided into two seasons. A data‐reduction technique which imposes variable smoothing upon the initial balloon‐position data complicates the analysis, but the existence of wind fluctuations with vertical half‐wavelengths between 300 in and a few kilometres is definitely established.A linear theory which takes into account the effects of rotation and temperature lapse rate upon such motions is briefly discussed. It is shown that the vertical flux of energy associated with the motions may be an important energy source for the atmosphere above about 80 km. A firm estimate of the magnitude of the vertical energy flux requires further information about the periods and/or the horizontal scales of the obser

ISSN:0035-9009    

DOI:10.1002/qj.49709239105

出版商:John Wiley&Sons, Ltd    

年代:1966

数据来源: WILEY

摘要:

AbstractThe contributions of various transport terms in the thermodynamic energy equation are calculated over the Northern Hemisphere for the four seasons. Local heating is found to be an order of magnitude less than the other terms. The computed fields due to mean horizontal motion cover a more extensive area than those of earlier investigations and extend over the Northern Hemisphere from surface to 100 mb for the four midseason months. An attempt to represent the effect of horizontal transient disturbances by relating it empirically to the mean temperature field is found to be unsatisfactory; direct computations are made of the eddy contribution over a large part of the hemisphere, for three successive winters and one summer. An estimate of the contribution due to vertical motions, both mean and transient, is obtained indirectly as the difference between results of the present study and those of earlier independent investigations of atmospheric heating.

ISSN:0035-9009    

DOI:10.1002/qj.49709239106

出版商:John Wiley&Sons, Ltd    

年代:1966

数据来源: WILEY

摘要:

AbstractA scheme is described for the calculation of the atmospheric infra‐red radiative cooling rate which is suitable for use at all levels. It uses the Curtis matrix method together with the Curtis‐Godson approximation in a form which includes the influence of temperature on line intensity. Doppler effect is included. Because of its simplicity the Goody random model is used for all the absorption bands considered (H2O rotation and 6.3μ, CO215μ, O39.6μ); the use of more accurate models as they become available presents no fundamental difficulty and in any case many of the topics investigated are not particularly sensitive to the spectral model used. A method of reducing the number of spectral intervals is described and its accuracy demonstrated. An accurate method of dealing with diffuse radiation is used to test the diffuse approximation, with the result that the constant factor 1.66 originally proposed by Elsasser is found to be quite adequate for most purposes. Cooling rate errors caused by the following factors are estimated: (1) random and systematic errors in the initial temperature and humidity profiles; (2) the size of the vertical step used in computation; (3) neglecting the temperature dependence of the Curtis matrix; (4) non‐linear effects in forming climatological means. It is shown that the easily computed ‘cooling to space’ is often a good approximation. All the error investigations are based on direct calculations of the cooling profile. Some comparisons with other techniques are presented and a number of examples of meteorological interest are used to illustrate the versatility of the comp

ISSN:0035-9009    

DOI:10.1002/qj.49709239107

出版商:John Wiley&Sons, Ltd    

年代:1966

数据来源: WILEY

摘要:

AbstractA simple model of a cloud in which drops of different sizes are assumed to be falling at their terminal velocities is used to study the development of drops with radii up to 40 μ by the coalescence mechanism.It is not clear what initial distributions of drop sizes should be used in this study and therefore the development of larger drops from several different distributions which are thought to be characteristic of the early stages of various types of cumuli are compared. In this part of the paper Hocking's (1959) values of the collection efficiencies are assumed to apply. It is found that large drops develop rapidly in maritime clouds, and for clouds characteristic of continental climates it is shown that the maximum drop radius needs to be greater than about 22μ for the coalescence mechanism to be effective. There must also be an adequate supply of drops with radii between 14 and 20 μ.The effects of small increases in the collection efficiencies which may be caused by various factors, such as turbulence or electric fields, are studied with the model using two different initial drop size distributions. It is found that the most important single parameter in determining the onset of the coalescence mechanism is the minimum drop size capable of capturing still smaller drops. Generally, a significant effect is found if the change in the collection efficiency is equivalent to increasing the radii of the interacting drops by more than about 2μ. It is suggested that any future computations or experiments to determine changes in the collection efficiencies should look for effects of this magnit

ISSN:0035-9009    

DOI:10.1002/qj.49709239108

出版商:John Wiley&Sons, Ltd    

年代:1966

数据来源: WILEY

摘要:

AbstractFlights have been made within frontal clouds over southern England to investigate the distribution of precipitation in the horizontal and the vertical through the systems. Several examples are presented. It was found that there is a large variability both in time and place on all scales which makes it difficult to produce a general description. In all cases the contribution to the total rain amount from the cloud layers well above the freezing level was small and the majority came from the lowest levels. In one case all the frontal precipitation was produced in the liquid phase. Some surprisingly high values of precipitation rate were found near cloud base and have not yet been explained.

ISSN:0035-9009    

DOI:10.1002/qj.49709239109

出版商:John Wiley&Sons, Ltd    

年代:1966

数据来源: WILEY

ISSN:0035-9009    

DOI:10.1002/qj.49709239110

出版商:John Wiley&Sons, Ltd    

年代:1966

数据来源: WILEY

摘要:

AbstractA statistical analysis of wind, air, dew‐point and sea‐temperature records from all nine weather ships in the North Atlantic shows local variations between years which are highly significant when compared with variations within months. The fluctuations show a consistent pattern with a scale of more than 500 miles in the atmosphere and a persistence over several months. The horizontal extent of sea‐surface temperature anomalies appears to be somewhat smaller, but they tend to last longer than air‐temperature anomalies.Short‐period variations in the flux of latent and sensible heat are due predominantly to atmospheric variations, particularly in winter. The effect of sea‐surface temperature anomalies is somewhat greater in summer, though it becomes significant only on the annual

ISSN:0035-9009    

DOI:10.1002/qj.49709239111

出版商:John Wiley&Sons, Ltd    

年代:1966

数据来源: WILEY