Abstract
The main aim of the study is to investigate the atmospheric circulation impact on snow cover duration (SCD) and maximum seasonal depth of snow cover (MDS) in Poland in the twentieth century. The most important is to answer four questions: (1) which of the two, macro‐ or mesoscale atmospheric circulation, dominates in influencing the snow cover variability and changes in Poland area? (2) which of the two, meridional (S–N/N–S) or zonal (W–E/E–W) advection, dominates in influencing the snow cover variability and changes? (3) are the atmospheric circulation–snow cover relationships stable with time or did they change in circulation epochs? (4) does any strong relation exist between the snow cover in Poland and the atmospheric circulation enabling the possibility to forecast the nival conditions for the next winter season?
The principal results of the study are as follows: (1) the macroscale circulation connected to atmospheric patterns over the Atlantic Ocean impacts stronger on the SCD variability in Poland than the circulation patterns located directly over the Poland area; (2) during the period 1966/67–1995/96 the zonal circulation dominated over the meridional one in influencing the SCD variability and change (the exceptions were areas with the most intensive foehn effect); (3) the decreasing trend of the dependence strength of the SCD on the meridional circulation with respect to the increasing tendency for zonal circulation‐SCD impact was observed in the twentieth century; (4) the meridional circulation dominated over the zonal one in influencing the SCD till the 1930s of the twentieth century only (5) the snow cover in Poland is positively correlated with the North Atlantic Oscillation (NAO) in October prior to the winter season.
The instability of the snow cover dependence on the atmospheric circulation in the twentieth century corresponds roughly to the circulation epochs and periods of intensity changes of the zonal/meridional advection over Europe. Copyright © 2007 Royal Meteorological Society