Assessment of the Drought and Wetness Characteristics over Bulgaria by Means of the Standardized Precipitation Index
摘要
Drought is a weather- and climate-related phenomenon of complex nature which is a usual part of the climate in Southeastern Europe and in particular Bulgaria. Regardless of the type of the drought, the reduction in precipitation with respect to the normal amount is the primary driver, resulting in a successive shortage of water for different natural and human needs. Among the used drought indices the Standardized Precipitation Index (SPI) could be outlined due to its various strengths and, subsequently, it is worldwide increasingly used in both research and operational modes. The study presents an assessment of the drought and wetness characteristics of Bulgaria for the period 2014–2022 by means of this index calculated from precipitation data from more than 150 measurement stations. The relatively high number of stations ensures high land coverage and spatial representativeness. The rather big amount of data as well as the sophisticated calculation procedure of the SPI (the computation of some special functions is needed) makes the considered problem computationally challenging. The study reveals, first of all, high spatial and temporal variability of the SPI over Bulgaria. Several short-term drought episodes are detected but the wetness conditions generally prevail.