ABSTRACT
In this chapter, the authors use larger-scale data sets that incorporate Bulgaria, the Balkans, and Europe. They draw upon the techniques to help understand the recent drought occurrences in Bulgaria. At the hemispheric level, climate in Bulgaria and the Balkans is strongly influenced by the Icelandic low and the Azores high over the Atlantic Ocean, as well as by seasonal pressure features, including the winter Mediterranean low and European and Siberian highs. Several research organizations have developed grid-based climate data sets that are useful for seeing Bulgarian climate in larger contexts. The occurrence of winter drought is particularly important, since winter snow accumulation is a critical source of spring-summer runoff in Bulgarian lowland streams. The spatial-dryness (SD) index for Bulgaria is defined as the proportion of the country that has precipitation in the lowest quintile of record. The period from 1982-1994 had five of the twenty driest years as indicated by the SD index.
