Vízügyi Közlemények, 1995 (77. évfolyam)
3. füzet - Mika J.-Ambrózy P.-Bartholy J.-Nemes Cs.-Pálvölgyi T.: Az Alföld éghajlatának időbeli változékonysága és változási tendenciái a hazai szakirodalom tükrében
284 Mika J.-Ambrózy Р.-В art holy J.-Nemes Cs.-Pálvölgyi T. Can trends, observed in the past, or the lack of trends be extrapolated for the future or not? In addition to trend analyses several attempts were made for detecting the periodicity of drought. These attempts have either failed or yielded results of low information content (in the light of the overall variability). The past 10-15 years belong to the driest periods. The past decade was the driest period since 1881, especially in the Alföld. This resulted in decreasing trends of the relative moisture content of the upper 1 m deep soil layer. The authors state that the assessment of future changes, expectable upon global changes in this part of Hungary, is hampered by the fact that no changes like those we are going to face, had been sufficiently documented by measurement data, that is no such changes had been experienced in the past. Assessment of the regional specific character of the climate is a more difficult task than those of the global averages, since the horizontal resolution of the presently applied climatic models is much smaller than what would be required for the appropriate description of atmospheric processes which determine local weather, with special regard to those affecting the development of clouds and the occurrence of precipitation. According to the climate scenario on the doubling of the carbon dioxide levels of the Meteorological Department of ELTE (Eötvös Loránd University of Arts and Sciences) both the probability of precipitation and the depth of precipitation water would be substantially lower than those of the past 50 years. A conditional forecast of the precipitation conditions of the catchment area of Lake Balaton (Figure 8.) indicated that the depth of precipitation water of rainy days would be lower that the present value in all points of the drainage basin (if the C0 2 level was doubled). In the winter months, however, a similar comparison indicated positive changes in the south-eastern third of the drainage basin. Forecasts made at the National Meteorological Service of Hungary indicate that in the summer half-year the air temperature of the country follows, with a positive multiplier factor of 1.0-1.6, the smaller changes of the average temperature of the hemisphere. In the winter, as contrasted to this, relationships to the annual mean air temperature of the continental ocean can only be demonstrated. Simultaneously with the smaller rise of the temperature of the hemisphere there is a steep fall of precipitation in Hungary, in the summer, characterized with a factor of 50-110 mm/K. In the winter half year there is no unambiguous change in the precipitation condition up to a half-degree rise of the hemisphere's average temperature. The combined effect of decreasing precipitation and increasing sunlight duration in the summer half-year makes the marked decrease of the soil's moisture content probable. In the case of an 0.5 °C rise of the average temperature of the hemisphere the frequency of months with less than 30% relative soil moisture content increases with almost 60% (0.8 month/year). * * * Zeitliche Variabilität des Klimas der Ungarischen Tiefebene von Dr. -Meteor. János MIKA. CSc., Dr.-Meteor. Pál AMBRÓZY. Dr.-Meteor. Judit BARTH OLY, CSC., Dr.-Meteor. Csaba NEMES und Dr.-Meteor. Tamás PÁLVÖLGY1 Die Grundprinzipien und die meisten Instrumente der meteorologischen und hydrologischen Messungen haben sich während der Jahrhunderte kaum verändert. Gerade diese Tatsache hat die Registriereung der sich langfristig abspielenden Veränderungen ermöglicht. Auch in Ungarn wurden die sog. Klimareferenz-Stationen festgelegt. Ihre Zeitreihen sollen einerseits die für größere Räume kennzeichnenden Veränderungen der einzelnen Klimaelemente enthalten, und sollen gleichzeitig
