Developing a regional drought climatology for the Czech Republic

Abstract

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 focussed 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 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.

Observed drought and wetness trends in Europe: an update

“…In the international literature there are several papers addressing the trend detection in drought episodes both at regional and large-scale level in Europe, using different data sources and methodologies (see for example Hisdal et al, 2001;Lloyd-Hughes and Saunders, 2002;Moreira et al, 2006;Briffa et al, 2009;Trnka et al, 2009), but no comprehensive study has been carried out with updated data. In agreement with our findings, all these efforts demonstrate the spatial variability of the detected trends and the crucial influence of the time records selected for the analysis.…”

Drought trends over part of Central Europe between 1961 and 2014

“…In the Czech Republic, however, drought trends be tween 1961 and 2000 or 2010 have been evaluated in several studies (e.g. Trnka et al 2009, Potop et al 2014. By contrast, comprehensive studies of this type have not been conducted for Slovakia or Austria, and comparisons have not been made with neighboring countries using station data.…”

Agricultural drought and spring barley yields in the Czech Republic

“…This is caused mostly by the local variability in climate, soil conditions and the overall level of agriculture practice during the evaluated period. The non-existent or very low correlations between the rZ-index and yield departures in the north-east and north-central regions are associated with comparably higher precipitation totals and a much lower probability of significant drought occurrence in these regions generally (Trnka et al 2007, Tolasz et al 2007. In order to capture the varying effects of drought in different regions, we carried out a specific analysis consisting of assigning the individual districts (Figure 5a) into six clusters.…”

“…The importance of the presented results for farmers, and decision-makers in general, becomes more obvious when we take into account the present and expected trends in the main weather variables that influence drought frequency and severity. The detailed analysis of drought trends across a large number of weather stations in the Czech Republic (Trnka et al 2007, Brázdil et al 2007 showed the tendency for more intensive droughts at the majority of the analyzed stations. According to most climate change scenarios, an increase of air temperature over Central Europe (which is accompanied by lower precipitation in summer months in some cases) should be anticipated (e.g.…”

“…The Z-index values used in the study were calculated for each of the 233 stations for the period 1961-2000 using the modification proposed by Trnka et al (2007). In order to better describe drought climatology of a particular region, the calculation procedure of the Palmer Z-index was modified and is referred to as the "relative Z-index" (rZ-index).…”