Hidrológiai Közlöny 1988 (68. évfolyam)
3. szám - Papp Zoltán: Vulkánkitörésekre visszavezethető anomáliák Magyarország csapadékmennyiségének időbeli eloszlásában
152 HIDROLÓGIAI KÖZLÖNY 1988. 68. ÉVFOLYAM, 3. SZANt Abstract: Volcanically generated anomalies in the temporal variation of precipitation of Hungary Papp, Z. Explosive volcanic eruption have been regarded as a possible cause of climatic change. After eruptions, the solar radiation and the sunshine duration, consequently the temperature of the troposphere are temporarily decreasing. Variations of these climatic factors from 1912 to 1914 are presented — as an example — in Fig. 1, using data from Hungary. Rate of the sunshine duration is expressed in hours/month (diagram A). B : Variation of the average monthly temperature compared to the 50-year mean value. C : Temperature variation of Budapest with respect to the 50-year mean, using data of temperature-pentades. D: Variation of the average monthly precipitation compared to the 50-year mean. The 50-year means are calculated for the years from 1901 to 1950 and are indicated by dashed line in all the Figs. 3—8. The superposed epoch analysis method is applied to examine the evident temperature falling and the decrease of annual and monthly precipitation amounts in Hungary, which are respectively due to large volcanic dust veils. Alternative groupings of the so-called „key dates" (the eruption years) are used as data bases and the strenght of the „volcanic signal" is determined in the two different cases. Table 1 shows the data of large eruptions, selected by their DVI (7)ust Feil Zndex) — and VEI (Folcanic Explosivity /ndex) — values. Table 2 lists the smaller eruption at the turn of the century. These are denoted by shaded isoscales triangle in all the Figs, i, 4, 5, 7,8. Results of the superposed epoch analysis are given in Fig. 2. Diagrams A and C show the variation in the four year periods preceeding and following the eruption year, while curves B and D, illustrate the variation of the annual mean precipitation in mm/year. The considered eruption years (the key vears) are indicated in the individual diagrams. The „volcanic signal" is about 0,5—0,8 C°, and it is greatest generally in the eruption year. Recovery time is about three years. A weak, but statistically significant „volcanic dip" have been revealed in the long-term precipitation record, as the most important result of the investigations in question. Amplitude of it is about 40—70 mm. The recovery time is less than four years. In order to assess the statistical significance of the decreasing precipitation, the i-test (based on the Student-distribution) has been applied, similarly to other authors. Results corroborate the existence of the supposed volcano-climatic interactions (Table 3). In the second part of the paper a number of remarkable anomalies in the temporal distribution of precipitation are investigated in more detail, using the annual and the monthly mean precipitation data, respectively (Figs. 3 — 8). Based on the monthly data, the recovery time of the greater anomalies is several months, while the amplitude is about 40—70 mm, as well. Remarkable is the undulating character of the variation of monthlv precipitation in the two year period, after the eruptions (Fig. 7) — the precipitation changes are superimposed on a sinusoidal half-wave. The superposed epoch analvsis method of compositing annual ring widths is applied to show an indirect evidence of supposed changes of volcanic origin, in the temporal variation of temperature and precipitation using data of five tree-ring records, from Hungary. A significant decrease in ring-width is visible in the eruption year and/or in the following years (Fig. 9). These remarkable minima can contribute the more reliable correlation of the overlapping of tree-ring records, which is very important in dendrocronology. Cause of the minima, indicated bv a question-mark in Fig. 9, is yet unknown. In the diagrams, ordinate of which is denoted by P c, the corrected values of the (annual) ring-width are considered in order to eliminate the natural decreasing in average thickness of the rings with the increasing age of the tree. It is concluded, that several period(s) of decreasing in the precipitation, registrated about the turn of the centurv, may be associated first of all with climatic effects of Krakatau (1883), Tarawera (1886), Bandai San (1888), Santa Maria (1902), and Katmai (1912) eruptions. volcanic eruption, anomalies of the weather, dendroclimatology, Student-distribution, superposed epoch analysis method A miskolci Nehézipari Műszaki Egyetemen 1976-ban szerzett geológus-mérnöki diplomát. 1982-ig a vízügyi ágazatban hidrogeológusként dolgozott, ezt követően a győri Széchenyi István Közlekedési ós Távközlési Műszaki Főiskola Geotechnika Tanszékére került, ahol a földtan, vízföldtan, mérnökgeológia és talajmechanika tárgyak előadója. Mint a talajmechanikai laboratórium szakvezetője, műszer-, mérés- és feltárástechnikai feladatokkal foglalkozik. 1985-ben „summa cum laude" minősítéssel doktorált vulkanológiából és geofizikából. A szeizmológia, fizikai földrajz, vulkanológia és klimatológia határterületeihez sorolható önálló kutatási eredményeit ezideig 15 tanulmányban foglalta össze — ezek egy része külföldi szaklapokban (Hollandia, Indonézia, Olaszország) jelent meg. PAFP ZOLTÁN
