Regional effects of synoptic situations on soil drought in the Czech Republic

Soil drought has an important influence on plant development. The SoilClim model was used to investigate episodes of soil drought with 10-year return periods at the 0–100-cm profile during the 1961–2017 period for four selected regions of the Czech Republic (North-western Bohemia, Southern Bohemia, North-eastern Moravia, and Southern Moravia). It emerged that the frequency of soil drought significantly increases in the summer half-year (SHY) and exhibits insignificant trends in the winter half-year (WHY). The dynamic climatology of soil drought is based herein upon synoptic situations as classified by the Czech Hydrometeorological Institute, in terms of which changes in the occurrence and precipitation intensity of drought episodes in the four individual regions were studied. Drought episodes are generally related to decreases in the frequency of precipitation-rich situations and in their precipitation intensity. This is particularly true of situations C (central cyclone over central Europe), B (trough over central Europe) and Bp (travelling trough). Situations B and Bp, together with south-west cyclonic situations SWc_1-3, appeared as the most relevant to regional differences in drought episodes during SHY in the four regions studied, while western cyclonic situations (Wc and Wcs) emerged as particularly important in WHY. Regional differences are clearly marked between the Bohemian and Moravian regions, especially in SHY. Discussion of the results obtained concentrates on the uncertainty of soil drought data, differences between SHY and WHY, the effects of synoptic situations, and the broader context of soil droughts.