Vízügyi Közlemények, 1935 (17. évfolyam)
Kivonatok, mellékletek - Kivonat a 4. számhoz
25 III . FACTORS DETERMINING THE CONDITION OF PRECIPITATION. By Dr. L. AUJESZKY. (Pages 683—696.) The only practically important way in which cloud and precipitation can be formed, is the rising of a large quantity of air to a considerable height of several hundreds or thousands of metres. In this way the air undergoes adiabatic cooling, and over-saturation of vapour ensues. First the over-saturated vapour is condensed to minute floating bodies (condensation nuclei), then around these cloud-drops or ice-crystals are formed. The limit of formation of cloud-drops and ice-crystals is not zero centigrade, but at considerably lower and varying temperatures, for a great overcooling of cloud-drops may be observed in the open atmosphere. The investigation and constant registration of temperature conditions in high strata (by means of balloons and météorologie aeroplanes) renders it possible to prepare differential prognoses which indicate whether precipitations will fall in the form of rain or snow. This advance in weather forecast is of practical significance, because it is important to know whether precipitation will take the form of rain or snow. With our climate, almost all rain is formed of snow which has thawed in the lower warm portion of its fall. The old isobar-prognostics could not foretell these important conditions, but the new methods of meteorology make it possible to ascertain them. The snow-layer has downwards (towards the soil) an effect of preserving heat, while towards the air above, it has a great and dangerous cooling effect, The disappearance of snow is a complicated and manifold météorologie process, the main factors of which arc the movement, of warm ah 1, evaporation into the dry-warm atmospheric mass (sublimation), the group of phenomena called főhn (adiabatic warming caused by wind sinking on the lee side of mountains, dispersion of cloud, drying of the air, and its excessive turbulent-drying movement), and finally in late springtime also the sunshine to a considerable extent, Contrariwise, in most of the intercurrent thawing in winter the sunshine has very little or no part, especially down in lowlands. With our climate, warm rainfall is a frequent factor in thawing snow. The evaporated part of the destroyed snow-covering rapidly moves to remote regions, and exerts almost 110 effect 011 the formation of our weather, or the discharge of our rivers. The melted part is divided between percolation and runoff ; this depends 011 soil conditions. Finally, 011 the basis of an idea of M. B. Kenessey's, the writer makes a study of the process which snow-coverings of the last 14 years have undergone. VI. MEASURING THE DISCHARGE IN OPEN CANALS BY PROFILE CONTRACTION. By Dr. Ing. W. LÁSZLÓFFY. (Pages 697—714.) The application of the method of profile contraction to measuring water volume in pipe conduits, in the form of the Venturi meter, is well known. The adjust-
