Á. DRÜSZLER, P. VIG, K. CSIRMAZ
ABSTRACT. Effects of Historical Land Cover Changes on the Precipitation Distribution in Hungary. The land cover changes were significant in Hungary in the 20th century according to examinations of historical maps and statistical databases. We used the MM5 non-hydrostatic dynamic model to further evaluate the effects of these land cover changes on precipitation. The dynamic model was run with the same data of detailed meteorological conditions for 26 cases, of 48 hours each, from 2006 and 2007, but with modified lower boundary conditions. The set of the 2x13 selected initial conditions represents the whole set of the macro synoptic situations (Péczely, 1983) for Hungary. The lower boundary conditions were generated for two selected time periods, about 1900 and 2000. In this way, 52 (2x2x13) forecasts were done with 48 hours of integration. The effects of land cover changes under different weather situations were further weighted by the long-term (1961-1990) the mean frequency of the corresponding macro synoptic types, to assume the climatic effects from these stratified averages. The results show that although the Hungarian land cover changes did not have a significant effect on the average precipitation nation-wide. The impact on the regional distribution of precipitation is considerable, especially under unstable weather conditions.
Key words: land cover change, precipitation, trigger effect, mesoscale modeling, MM5.