Effects of atmospheric circulation on ice conditions in the southern Baltic coastal lagoons

Abstract

AbstractRelationships between atmospheric circulation patterns and ice conditions in the southern Baltic coastal lagoons were explored. Ice data consisted of number of ice days (L) and duration of ice season (S) in the Szczecin Lagoon (off Karnin), the Puck Bay (off Puck) and the Vistula Lagoon (off Krasnoflotskoye) from 1950/1951 to 1989/1990.Atmospheric circulation patterns for the period studied were extracted from Lityński's ‘Calendar of atmospheric circulation types’ developed at the Institute of Meteorology and Water Management (IMWM). A circulation pattern was identified by three numerical parameters: the zonal circulation index, the meridional circulation index, both pertaining to a zone delimited by coordinates 40–60°N, 0–35°E, and the surface pressure index for Warsaw.The number of days with individual atmospheric circulation patterns occurring from October to March was calculated. Subsequently, the selected patterns were combined by wind direction sectors and several month‐long periods that most closely correlated with ice conditions. The highest linear correlation coefficients (r>0.8) were obtained for the relationship between the number of days with winds from the east from December to February and December to March and the winter number of ice days (L). Somewhat higher were multiple correlation coefficients with winds from the east and west as circulation type predictors. Slightly lower correlation coefficients for the sectors and circulation periods mentioned were obtained for the duration of the ice season (S), although some of the coefficients were significant even at the probability level of α=0.01.Higher correlation coefficients were obtained for correlations involving ‘cold’ circulation patterns (sector NE+E+SE winds) and ice conditions than for those involving ‘warm’ patterns (sector SW+W+NW). Copyright © 2001 Royal Meteorological Society