Hydroclimate variability in the Czech Republic studied through subjective and objective classifications of atmospheric circulation

Investigation of the relationship between climatological variables and circulation patterns expressed by various classifications of circulation types is a key procedure in synoptic climatology. This study provides new insights into circulation drivers of hydroclimate based on an analysis of precipitation and soil drought in multiple parts of the Czech Republic with respect to the subjective classification of the Czech Hydrometeorological Institute and objective classification based on the flow strength, flow direction, and vorticity during the 1961–2020 period. Circulation types are investigated in regard to their contributions to the total precipitation, mean daily precipitation totals, and precipitation probability. Types with a westerly airflow and a trough over Central Europe exhibit the highest proportions in precipitation totals. Types with a cyclone over Central Europe, especially combined with a northwestern or northeastern airflow, result in the highest daily mean totals and precipitation probability. Types with a southwestern airflow transport more precipitation to western parts of the Czech Republic, while those with a northeastern airflow transport more precipitation to the eastern parts, with a slight seasonal shift in the gradient axis between winter and summer. Circulation drivers of drought episodes are investigated based on soil-drought values calculated from the SoilClim model. Increased frequencies of north-eastern anticyclonic types, and decreased frequencies of directional and cyclonic are important for the origin and course of soil-drought episodes. In addition, the suitability of both classifications for long-term trends analysis is investigated.