Drought Analysis In Slovakia: Regionalization, Frequency Analysis And Precipitation Thresholds

The paper presents a drought characterization for Slovakia based on the standardized precipitation index at the time scale of three months (SPI3) applied to the precipitation records at 491 Slovakian rain gauges over a considerable span (33 years). After a drought spatial regionalization, using Principal Component Analysis (PCA), the kernel occurrence rate estimation method coupled with bootstrap confidence band was applied to characterize the yearly drought occurrence rates in each one of the regions given by the PCA, aiming at identifying trends in the frequency of the droughts. The study also includes examples of surfaces of precipitation thresholds that can be easily and reliably utilized to recognize and monitor the drought occurrences at the early stages of their development. Those surfaces were obtained by reverting to the original precipitation field the values of the SPI that represent drought limits.