Meteorological features behind spring runoff formation in the Nemunas River

This paper is concerned with atmospheric circulation as the central factor influencing snow melting conditions and consequently the spring runoff characteristics of the Nemunas River. The analysis includes snow water equivalent (SWE) accumulated before the start of snowmelt runoff and its relationship with maximal water discharge and flood volume. The results show that the relationship has a dipolar character. The cohesion between SWE and the maximal runoff was divided into two different groups: A and B. The increasing maximal values of SWE correspond to the rapidly increasing maximal water discharge during the runoff seasons in group A and slowly increasing discharge in group B. Intensive snow melting following significant warm advection in the lower troposphere or, conversely, dominant radiative snow melting despite the high values of snow water equivalent, cause the high magnitude spring floods of the Nemunas River. The importance of atmospheric circulation increases during the beginning of the spring runoff in particular.