Zusammenfassung. Nach einer einleitenden I)iskussion der im Vergleich zum strahlungsundurchl~ssigen Erdboden bei einer Schneedecke hervortretenden besonderen ~r wird im Abschnitt Iim Ansehlu2 an eine frfihere Arbeit yon mir das Problem der n~ichtlichen Abkiihlung der Schneeoberflache behandelt, [Inter der Annahme einer konstanten effektiven Ausstrahhmg w(irde sich dabei mit Verwendung der in der Literatm" angegebenen Betrage der Wgrmeleitfiihigkeit im Schnee eine enorm groi3e, welt aLd~erhalb der Erfahrung liegende Abktihlung im Laufe einer Strahlungsnacht ergeben. I)araus wird der SchluI~ gezogen, da2 die tats~chlich wirksame W&rmeleitung im Schnee in den obersten Schichten etwa das 7-bis 8fache der in der Literatur (u. Die unmittelbare Folgerung daraus ist, daI~ die in der Literatur u. a. yon ABELS aus dem t~glichen Temperaturgang in einer Sehneedecke nach der Poissonschen Formel berechneten Betr~ige der W~rmeleitfiihigkeit unrichtig sind und einer Korrektur bediirfen.aDabei zeigt es sieh, da~ die Verringerung der Amplitude mit der Tiefe beim Schnee gr61~er ist als sich aus der Poissonschen Formel ergibt, w'~hrend die VerzSgerung der Phasenzeiten sich nicht in demselben Mal3e unterscheidet. Dadurch finder eine yon KE~X~]~N besonders erw~hnte Tatsache, da2 n~mlich die aus den Amplituden berechneten Koeffizienten der W~irme-leitung durchwegs kleiner sind als die aus der Verz6gerung der Phasenzeiten sich ergebenden, bier ihre Erkl~irung.Summary. After an introductary discussion of the particular features of surface layers of snow compared with the conditions existing in soil that is impervious to radiation, in chapter I --in addition to a former paper of mine --the problem of nocturnal cooling of the snow surface is dealt with. Presupposing a constant net loss of heat by radiation from the snow to the atmosphere (effective outgoing radiation) and employing the data put down in literature of the conductivity of heat in snow an enormously big amount of cooling of the snow surface far beyond experience would result in the course of one night. Hence the conclusion has been drawn that the transfer of heat in the highest layers of snow must make up about 7--8 times the figures put down in literature by ABELS and others which are based on observations of the diurnal waves of temperature in snow layers. For this effect we assume an eddy conductivity, respectively a convection in highest layers of snow of less density.In chapter II the distribution of temperature in snow is calculated presupposing a constant effective outgoing radiation and at the same time a constant solar radiation. For that. short-wave solar radiation snow is pervious in contrast to ground. A special feature in that case is that the maximum of temperature does not appear on the surface as it is in the case of soil being impervious to solar radiation, but some centimeters below it. A formula is derived for the depth and the amount of this maximum.The theoretical results compared with the observations in snow layers give a good agreement between theory an...
Because of the fact that too many factors influence the nocturnal cooling of the ground surface, simplifications are necessary in order to derive a convenient formula giving the amount of cooling from sunset to sunrise. These simplifications must be justified both theoretically and practically. The solution is finally found by semiempirical methods. For the practical application of this cooling formula a diagram is constructed. A test of the results using observations for Vienna shows a good agreement between the predicted and observed temperature minima.
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