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
Az Alföld éghajlatának időbeli változékonysága és változási tendenciái... 283 Zilinyi V.: Kvalitatív és kvantitatív éghajlati idősorok statisztikai jellemzése. In: MMT XXVII. Vándorgyűlés, Debrecen, 1993. augusztus 23-25, 1993. WMO: Methods of correction for systematic error point precipitation measurement for operational use. WMO. No. 589. OHR No.21„ 1982. * * * Time variability of the climate of the Hungarian plains Alföld by Dr. ./. MIKA, Dr. P. AMBRÓZY. Dr. J. BARTHOLY, Dr. Cs. NEMES and Dr. T. PÁLVÖLGYI meteorologists The basic principles of meteorological and hydrological measurements have hardly changed during the last century and many of the instruments have also remained basically the same. This provided relatively good basis for recording (assessing) long term changes. Reference stations for detecting climate changes have been established also in Hungary. The stations were selected in such a way as to be representative for expectable changes in various climate elements of the time series and to represent changes over larger regions. At the same time the time series must be free from inhomogeneities stemming from both the local environmental effects and the changes of measuring/monitoring techniques. Three such reference stations have been selected in the Hungarian plains Alföld. In the middle of the sixties, however, there have been some changes made in the measurement of temperature, air moisture, wind direction and wind velocity (daily four measurements instead of the earlier three ones). This error (Figure 1.) could be corrected when calculating averages, but recent homogeneity analyses (Figure 2) have indicated that the correction made for the climate data series was inappropriate, at least in the case of temperature. The authors have analyzed the annual variability of some of the climate elements which are essential for calculating water budgets. Results of analyzing nation wide long term tendencies have also been summarized, focussing on the last 10-15 years that proved to be critical from the hydrological point of view. Special attention was paid to high precipitations of short time base (Figure J). Analyzing climate changes of the Alföld it can be stated that there had been substantial changes also in the past, as revealed by paleoclimatic analyses, and that they were coinciding with the cycles of hemispherical scale of the glacial-interglacial sequences. However, data series for mathematical trend analysis are available for the past one-or-two centuries only. In this context international experiences indicate that great care should be taken in analyzing the homogeneity of data series produced by instruments. Nevertheless, inhomogeneity stemming from the changes of observation times does not concern temperature, as this parameter is being measured by other instruments (preserving the minimum measured value). Annual national minimum temperature values exhibit arising trend (Figure 4.) Inter-annual variability of the annual, seasonal and monthly sums of precipitation indicated multiannual drier and wetter periods. Half-yearly sums of winter-time precipitation can be approximated, beyond 1901, by a mildly arching parabola, having its maximum in the thirties, and a decreasing limb afterwards. Ninety year trends of the summer half-year exhibit significant linear decrease (Figure 5.) Increasing frequencies of occurrence of warm-dry years and seasons can be detected in the past decade (Figure 6.) in the light of the combination of the two major meteorological elements. On the basis of the results of trend analyses the authors made statements on three frequently discussed issues: Can revealed tendencies prove the assumption of warming-up, due to the "green-house effect"? An even more disputed question is whether the variability of the climate is increasing or not, and whether extremities are increasing or not?
