Thunderstorm Clouds Research Articles

Further experimental evidence for the importance, with respect to thunderstorm electrification, of NO3′ ions contained in precipitation

Results of continued experiments that have in the meantime been carried out both in the free atmosphere and in the laboratory, have further confirmed the assumption of an atmospheric electric feed-back process. It originates from nitrous gases being formed by electric discharges which take place in zones of turbulence in the cloud space. The gases are dissolved in precipitation particles which thus receive a certain NO3′ ion concentration depending on the intensity of turbulence and on the atmospheric activity. The ion concentration gradient in the solid ice particles determines the amount of electric charges carried away by the individual pieces which are formed by fragmentation of the ice particles. The fragment having the higher NO3′ ion concentration is charged negatively with respect to the other. If the concentration ratio of the ice fragments separated from each other is e.g. 1:10, the amount of electric charge separated is 7 × 10−8 C/g of ice splinters. In the case of homogeneous distribution of NO3′ ions throughout the crystals there is no charge separation. On the basis of these results it is possible to explain both the avalanche-like increase and the collapse of the atmospheric electric activity in individual thunderstorm cells as well as the formation of the principal space-charge zones of the thunderstorm cloud.

Line type angel echoes observed at Dum Dum Airport, Calcutta

Two instances of line type angel echoes as observed on the scope of a high powered 3-cm radar at Dum Dum Airport, Calcutta, have been presented in this paper. These appeared in the vicinity of thunderstorm cloud cells and were detected prior to the occurrence of surface squalls. The possible sources of the angel echoes have been discussed. It has been suggested that the line type angel echoes were due to undercutting of the weather front.

Dependence of Freezing Temperature of Supercooled Water Drops on Rate of Cooling

The dependence of the median freezing temperature of supercooled water drops on rate of cooling is studied over a wide range of cooling rates. A polished metal surface, coated with a water repelling film of liquid paraffin is used to support the water drops being frozen. Deeper supercooling is observed with higher cooling rates in the range 0.3 to 5.0 deg C min−1. However, for cooling rates greater than 5.0 C min−1 a reverse trend is indicated and the drops freeze at warmer temperatures. The importance of tins experimental result is discussed in the case of thunderstorm clouds with strong updrafts. A similar effect for sublimation nuclei tested in cold chambers has been noted by Schulz (1947) and by Smith and Heffernan (1954).

Meso-scale study of Rainfall over Poona and neighbourhood

A meso-meteorological network of autographic raingauges and microbarographs was established in every mile square of 36 square miles centred round the Poona Observatory. Spells of thunderstorms occurred only in association with large scale disturbances observable on synoptic charts-Rainfall from a single thunderstorm cloud was found to be about 7 x106 metric tons- Monsoon rainfall showed significant variations both in time and space and was not made up of steady and continuous rain as is often believed. A strengthening of the monsoon rainfall is associated with a large number and higher intensity of rainspells and not with any increase in the duration of rainspells.

A theoretical study of the conductivity of air in thunderstorms

By considering the boundary conditions at the surface of a thunderstorm cloud, it can be shown that most descriptions of the charge configuration found in these storms are compatible with relatively high electrical conductivity within the cell. The problem is formulated by having a vertical column of current carry positive charge upward and deposit this charge in a spherical region of space. The only electrodynamic quantity not included in the analysis is the time variation of the magnetic field. The solutions are then studied in terms of spatial variations in the electrical conductivity. It is concluded that observations made on active thunderstorms agree best with a situation in which a relatively high electrical conductivity is developed within the cloud.

The effect of an external electric field on the supercooling of water drops

The effect of electric fields on the supercooling of water drops was studied by a special experimental technique which permitted the observation of the action on water drops of a dc electric field of 1 to 30 kv/cm. These experiments, documented by a motion picture film, showed that freezing could be initiated in the water drops at a temperature which was only a few degrees below 0°C by applying external electric fields which had field strengths of several kilovolts per centimeter. It was found that the electrofreezing effect was not due to an orientation of water molecules in the water sample, nor was it due to participate matter produced by sparks or corona discharges since no such discharges took place during the experiments. It was found that the effect was a consequence of the movement of the drop in the electric field along a solid surface. It was concluded from the experiments (1) that an external electric field is able to activate the ice-micleability of a solid surface and (2) that the characteristics of the effect make it very unlikely that freezing can be initiated by electric fields in atmospheric clouds since the solid surfaces with which the drops have to be in contact during their deformation are not present in mature thunderstorm clouds.

PRESENT STATE OF RESEARCH ON ATMOSPHERIC ELECTRICITY

Introduction 292 1. Basic Information 294 2. Two Theories 297 3. Vertical Structure of Field, Conductivity, and Current in 299 4. Distribution of Space Charge in the Atmosphere 302 5. Time Variation of Field and Potential at High Altitudes 303 6. Description of Electric Processes in Regions of Good Weather 305 7. Electricity of Stratified Clouds 307 8. Electricity of Cumulus and Cumulus Congestus Clouds 311 9. Structure of Shower and Thunderstorm Clouds 313 10. Accumulation of Charges in Thunderstorm Clouds 316 References 320

On the question of cold air production beneath thunderstorm clouds

При помощи простой модели решается вопрос, какнм законом управляется растекание холодного воздуха из области осадков под грозовыми облаками. Из теории вытекает, что псевдохолодный фронт перемещается равномерно ускоренным движением. Равным образом была определена длительность существования псевдохолодного фронта и выведено соотношение для внезапиого повышения давления, сопряженного с переходом фронта. Оценки порядка покаяывают, что результаты в основном можно сравнивать с действительностью.

Radar echoes from lighting

AbstractPhotographic observations of radar echoes received from lightning are given and are used to suggest a possible distribution of the electric charge within a thunderstorm cloud.

A LIGHTNING STROKE FAR FROM THE THUNDER STORM CLOUD

School Science and MathematicsVolume 27, Issue 1 p. 96-97 A LIGHTNING STROKE FAR FROM THE THUNDER STORM CLOUD First published: January 1927 https://doi.org/10.1111/j.1949-8594.1927.tb05158.xAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume27, Issue1January 1927Pages 96-97 RelatedInformation

THE PIC DU MIDI OBSERVATORY

IN a recent number of La Nature, M. L. Rudaux gave an interesting account of the present condition and operations of this important mountain station. France is well provided with high level stations, and the observations from seven of them are published daily in the Bulletin International of the French Meteorological Office. An account of the very favourable position of the Pic du Midi station, and of the almost insuperable difficulties experienced by its original founder, General de Nansouty, was given, in considerable detail, by M. R. Radau, in his useful little work on “Mountain Observatories” (Paris, 1876), and has been summarised by Mr. A. L. Rotch in the American Meteorological Journal. The summit, which has. an elevation of 2877 metres (the observatory being 17 metres lower), is situated on the outskirts of the Pyrenees, in lat. 42° 56′ N., and long. 2° 12′ W. of Paris, and affords one of the finest views in Europe. Towards the north an immense plain stretches as far as the eye can see, and to the north-west, on very clear days, the blue waters of the Atlantic are visible, at a distance of 160 km. It lies directly in the path of the great atmospheric disturbances which traverse the Bay of Biscay, while the summit mostly enjoys a clear and luminous atmosphere, being some 200 metres above the level at which thunderstorm clouds usually gather. These advantages early attracted the attention of astronomers and scientific men; M. F. de Plantade died in 1741 while observing at the ridge which has since taken his name.