Vízügyi Közlemények, 1997 (79. évfolyam)

4. füzet - Ambrózy Pál: A Felső-Rába vízgyűjtőjének éghajlati jellegzetességei

A Felső-Rába vízgyűjtőjének éghajlati jellegzetességei 515 Péczely Gy.: Magyarország makroszinoptikus helyzeteinek katalógusa (1881-1983). OMSZ Kisebb Kiadva. No. 53. Budapest. Steinhauser, F.: Verteilung der Häufigkeiten der Windrichtungen und der Windstärken in Österreich zu verschiedenen Tages- und Jahreszeiten. Arbeiten aus der Zentralanstalt für Meteorologie und Geodynamik. Heft 53. 1982. Wakonigg, H.: Witterung und Klima in der Steiermark. Verlag Technische Universität, Graz 1987. * * * Climatic characteristics of the Upper Rába river catchment by Dr. Pál AMBRÓZY meteorologist From the point of view of regional atmospheric processes (e.g general circulation, weather fronts) the relatively small catchment can be considered a uniform one. Nevertheless, the highly varying topography and altitudes (between 150 m and 1500 m) results in substantial temporal and spatial differences in the values of climatic elements. There are no significant differences in the number of sunny hours (1850-1900), but the annual amplitude is less in the summits than in the lowland plains (Table I.). The direction of the basic flow, as defined by the general global circulation pattern of the atmosphere, is western north-western, but it becomes non-recognizable at some location due to the effects of the topography (mainly to that of the valleys of north-south direction). The frequency of wind direction is shown in Figure 1. The characteristic local wind of the Alps, the foehn, occurs only in the north-western part of the Rába catchment. Monthly and annual values of cloudiness are shown in Table 11. Fog generates (Table III.) mostly in the high mountains and in their closed basins and valleys. Average wind velocities of the Rába river basin are shown in Table III Monthly and annual average air temperature values are given in Table IV., while their dependency on the altitude is illustrated by Figure 2. The multiannual average highest annual temperature decreases from 33 °C of the low land parts to 25 °C of the 1500 m elevation. At the same time, however, the average of absolute minimum temperatures (-17 °C) hardly changes with the elevation, a phenomenon that might be explained by the high frequency of winter temperature inversions. On the other hand it shows (Figure 3.) decreasing trend from west to east, due to the increasing continental effects. The areal istribution of annual average precipitation is shown in Figure 1. June and July are the months of highest precipitation in all places, while the minimum occurs in January or February (Table V). Mediterranean effects (secondary maximum in the fall) can be identified in the lower, that is in the Hungarian, parts of the basin only. 60-69 per cent of the annual precipitation falls in the summer half-year. Monthly precipitation sum shows high variability (Figure 5.). It can be zero millimeter in any of the months of the winter half year. Nevertheless it also can be as high as 100 mm in any month and at any place, while it can exceed 200 mm between May and September. Table V provides information on the ever highest daily precipitation. Characteristics of snow coverage (snowy days, days of snow cover, average maximum snow depth, dates of the first and last day with snow cover) are given in Table VI. * * *