Vízügyi Közlemények, 1998 (80. évfolyam)
4. füzet - Rövidebb tanulmányok, közlemények, beszámolók
646 Rákóczi Ferenc Relationship between the cloudiness and precipitation on the two hemispheres By Prof. Dr. Ferenc RÁKÓCZI Meteorologist The global cloudiness of the Earth is discussed at the hemispheric scale. The major objective was to identify relationships between the multiannual monthly cloud coverage and the precipitation. Multiannual average monthly precipitation and the degree of cloudiness (N), calculated in various ways as percentage, are shown in Table I. Different indices of cloudiness are marked in different manner: the cloudiness as introduced by Rákóczi (1989) is marked by NR; Cloudiness values of Brooks (1927) are referred to as NB, while the cloudiness referenced to the seas, as defined by Rákóczi using the zone averages of Warren et al. (1988) is marked by NT. It can be seen that both precipitation and cloudiness are characterized by a seasonal pattern. Maximum values are detected in the summer, while the minimum cloudiness is measured in the winter months. Relationship between cloudiness and precipitation are shown in Figure 1. On the Northern Hemisphere the data pairs of multiannual average monthly global cloudiness and precipitation are hardly scattered. Scattering of the respective points is so low as if it was measured in laboratory. Low cloudiness values are associated with relatively high precipitation values, while medium values correspond to low precipitation. High cloudiness values repeatedly correspond to high precipitation. Based on these physical facts the relationship can be described, on the Northern Hemisphere, with second order polynomial. On the Southern Hemisphere the relationship between global cloudiness and precipitation is quite different. Scattering of the points is high. The higher scattering is due, most likely, to the less dense monitoring network of the Southern Hemisphere and to the higher uncertainty of the determination of the hemispheric precipitation values. On the Southern Hemisphere low cloudiness is associated with low precipitation and high cloudiness with high precipitation. This can be explained by the fact that 81% of the Southern Hemisphere is covered by oceans, having a high regulatory effect on each of the climate elements, thus also on precipitation and cloudiness. A marked linear relationship was identified for this hemisphere. Beziehung zwischen Bewölkungsverhältnissen und Niederschlag der beiden Hemisphären von Prof. Dr. Ferenc Rákóczi, Meteorologist Die globalen Bewölkungsverhältnisse der Erde werden im hemisphärischen Maßtab behandelt. Die grundlegende Zielsetzung ist, eine Beziehung zwischen der langjährigen durchschnittlichen monatlichen Wolkendecke und dem Niederschlag zu ermitteln. Die langjährigen durchschnittlichen monatlichen Werte der Niederschlagssumme und der mit verschiedenen Methoden errechneten - und als Prozentwerte angegebenen — Kennzahlen der Bewölkung (N) sind in Tabelle 1 ausgewiesen. Dabei wurden die nach der Methode von Rákóczi (1989) ermittelten Werte mit N R, die nach Brooks (1927) errechneten Werte mit N B, und schließlich die auf das Meer bezogenen — ebenfalls durch Rákóczi, unter Anwendung der zonalen Mittelwerte von Warren et al. (1988) errechneten — Werte mit Nj bezeichnet. Es ist zu erkennen, daß sowohl der Niederschlag, als auch die Bewölkung einen eindeutigen jährlichen Gang aufweist. Die Maxima melden sich im Sommer und die Minima der Bewölkung im Winter. Die Beziehungen zwischen Bewölkung und Niederschlag werden in Bild. 1 gezeigt.
