Synoptic conditions of the occurrence of snow cover in central European lowlands

Abstract

AbstractIn the central European lowlands, snowiness increases meridionally from the south to the north and latitudinally from the west to the east. Taking into account the spatial variability in the occurrence of snow cover, four regions of snow cover were distinguished using the principal component analysis (PCA). Furthermore, circulation patterns responsible for intense snowfalls and persistence of snow in each region were analysed. Composite maps of the sea level pressure (SLP) and 500‐hPa geopotential height means and anomalies were constructed for the days on which snow depth increased by ≥ 5 cm and for days on which the snow cover lasted for at least 3 days. Contour maps show negative anomalies of SLP and 500‐hPa heights over central Europe, associated with organized low‐pressure systems. The lows may differ in the intensity and localization, depending on the region. In the south‐western part of central Europe, heavy snowfalls usually appear as a result of cold‐air fronts in the colder parts of Mediterranean cyclones, the centres of which are often situated over the Italian Peninsula. Another typical location of cyclones or troughs of low pressure causing heavy snowfalls is the Baltic Sea region, where meteorological fronts appear quite frequently. Such a location of cyclonic systems causes snowfalls particularly frequently in the most snowy north‐western part of central Europe. The cyclonic activity over the continent that brings snowfalls is simultaneous to the weakening of Icelandic Low and significant positive SLP anomalies over the north Atlantic. The persistence of snow cover in the central European lowlands is possible under the positive anomalies of SLP over most of the continent, except for its south‐western part where weak negative anomalies are observed. At the same time, positive anomalies of 500‐hPa geopotential heights appear over the northern Atlantic and Scandinavia. Copyright © 2010 Royal Meteorological Society