Driving role of snow cover on soil moisture and drought development during the growing season in the Czech Republic

This study presents a detailed analysis on the role of snow cover during the cold season (October-March) on soil moisture deficit and drought development during the growing season (April-September) in the lowland and highland sites in the Czech Republic. Besides daily, weekly and seasonal series of basic snow-cover characteristics [the first day and the last day of snow cover, the number of days with snow cover (DSC), snow depth and snow water equivalent (SWE)] and soil water content measurements, six drought indices have been used in this study to quantify drought. Accumulations of years with significantly below average DSC/SWE were recorded in the early 1960s, mid-1980s, late 1990s and most of the 2000s. The trend towards an earlier end date of snow cover is found in both lowland and highland sites. However, the most significant shift in the dates of early end of snow cover has been identified to occur mostly in the hilly areas while in the lowland areas, these changes are not that evident. Liquid precipitation more than solid precipitation (snowfall) during the cold season lead to weakening correlation between SWE/DSC and the subsequent early summer (April-May-June, AMJ) soil moisture. Snow-cover characteristics can significantly influence soil water saturation during the first part of the growing season, while seasonal amount of SWE can explain up to 45% of soil moisture variability during AMJ season. More than 52% of dry AMJ followed after cold seasons with poor snow, and 42% of wet AMJ season followed after cold seasons with abundant snow. The strength of correlation between drought indices and soil moisture anomalies is higher in later summer. The negative anomalous snow characteristics in conjunction with winter and AMJ drought amplify lingering impact on the depletion of soil moisture in the later summer.