Fundamentals of geology I. (lithosphere) 1 1. The formation of the Earth 1


Fig. 12.8. Annual mean temperature of Hungary (www.met.hu)



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Fig. 12.8. Annual mean temperature of Hungary (www.met.hu)

4. Annual mean precipitation: The annual precipitation amount in Hungary is 500–750 mm, but there are remarkable differences between different regions. The spatial distribution of the annual precipitation amount shows double effects. The effects of the altitude and the distance from the Mediterranean Sea are important, but the Atlantic ocean also influences our climate. A hundred meters increase in altitude equals to about 35 mm extra in the annual amount, while the growing distance from the seas means a decrease. The wettest are the southwestern areas of the country and the mountains, where the amount could exceed 800 mm. On average, the low altitude valley of the river Tisza receives the least precipitation, the value does not reach 500 mm. Roughly, the annual sum decreases from SW to NE.



Spatial and year-to-year variability is notable in Hungary. The most precipitation falls between May and July, while the least between January and March. Due to a stronger cyclone activity there is a secondary maximum in most parts of the country during the autumn - this is particularly true for Southern Transdanubia. Its temporal uncertainty is shown in the fact that in the wettest years three times as much can fall than in the driest years, and zero precipitation can occur in any month. The country-wide annual precipitation amount showed a decreasing tendency during the last century, the decrease in 109 years was nearly 10 percent (Figs. 12.9., 12.10.).



Fig. 12.9. Distribution of annual mean precipitation (www.met.hu)



Fig. 12.10. Annual mean precipitation of Hungary (www.met.hu)

5. Wind conditions: Two main effects are characterizing the wind conditions of Hungary, the base flow determined by the general circulation and the modifying influence of the topography. Wind is distinguished into its direction and speed. The direction of the wind means where the wind blows from. In the upper air of the temperate climatic zone the prevailing winds are the Westerlies, but at lower altitudes they are significantly modified by the topography. Due to the location of Hungary the prevailing wind is the northwestern, while the southern winds are secondary maxima (Fig.). The northwestern base flow of the general circulation is more emphasized in Eastern Transdanubia and between the rivers Danube and Tisza, while east of the Tisza the prevailing wind is northeastern. However, due to the different circulation patterns the wind direction is not permanent, the relative frequency of the most frequent wind is only around 1535% in Hungary. Thus, in 6585% of the time the wind does not blow from the prevailing direction. On average, there are 122 windy days per year in Hungary (i.e. when the strongest gust exceeds 10 m/s), from which 35 days are gale (i.e. the strongest gust exceeds 15 m/s) (Fig. 12.11.).






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