Developing a Regional Drought Climatology for the Czech Republic

This study presents a methodology for the analysis of a drought climatology within a particular region that enables a user to define drought areas at a high spatial resolution. It is suitable for quantifying the relative differences in the intensity of drought spells, and the frequency and duration between individual stations within an area of interest. The methodology is based on the Standardized Precipitation Index (SPI), the Palmer Drought Severity Index (PDSI), and the Palmer Z-index (Z-index). However, the climatological parameters needed to process and calculate the indices were not derived separately for each site as is usually done but were based on a set of all available weather stations in the studied region. This approach was utilized in the case study including all of the Czech Republic using 233 climatological stations with monthly records of mean temperature and precipitation for the period 1961–2000. The study is also focused on the development of more efficient ways of communicating results to the stakeholders. Therefore, a method allowing for an integration of several drought indices into a single indicator called the Integrated Climatological Drought Indicator (ICDI) was developed. The newly developed method allowed for an objective identification of the T R N K A E T A L . , I N T E R N A T I O N A L J O U R N A L O F C L I M A T O L O G Y 2 9 (2 0 0 9 ) 2 drought-prone regions of the country that were defined as areas with a chance (higher than 50 and 60% respectively) of moderate or extreme drought. We have found that 12.3 and 3% of the country area, respectively, belong within these categories and that these regions also happen to be prime agricultural areas. The conclusions were supported by the results of a cluster analysis. Finally, the analysis of time trends was conducted, which showed that the majority of 233 stations had grown significantly drier during the studied period. The main driving force behind this development was found to be an increase of temperature, especially in the 1990s.