The Thermal State of the North Atlantic Ocean and Hydrological Droughts in the Warta River Catchment in Poland during 1951–2020

This study presents the direct relationships between changes in annual surface temperature of North Atlantic (SST) and number days per year experiencing low flows Warta River catchment (WRC) Central Europe, Poland, multi-annual period 1951–2020. The (TLF) was used to describe conditions hydrological drought WRC. Moderately strong (r~0.5) but statistically highly significant (p < 0.001) were found TLF SST subtropical (30–40° N, 60–40° W) subpolar (70° 10° W–10° E). With increase these parts Atlantic, a WRC also increased. It determined that besides synchronous (i.e., same year) SST, asynchronous relations occurred: one ahead changes. sunshine duration air increased, while relative humidity decreased. precipitation negative (from −0.04 −0.14), insignificant > 0.2). indicates impact on is mainly caused by shaping amount evaporation, which strongly increases years high climatic water balance becomes negative, resulting an extremely flows. analysis causes shows control, through height geopotential (h500), atmospheric circulation over Europe. In periods h500 growth pressure (SLP) increases. That area more frequently than average under influence Azores High; this leads frequency anticyclonic weather. A TLFs prolonged after 2000 are associated with tropical Atlantic.