Synoptic pressure patterns associated with major wind erosion events in southern Sweden (1973-1991)

Wind erosion causes severe damage on sandy soils in agricultural areas of north-west Europe. The weather conditions during erosion events are the result of the general atmospheric circulation and are key components in the erosion process. Principal component analysis (PCA) in combination with a non-hierarchical cluster analysis was conducted on de-seasonalized daily mean-sea-level pressure (MSLP) patterns of north-western Europe between 1973 and 1991 to determine the main synoptic types associated with wind erosion on sugar beet fields in Scania, southern Sweden. Cluster analysis of the PCA scores indicated that the observations should be grouped into 14 classes for which average MSLP patterns were computed. To assess the relationship between the patterns and wind erosion, 2 indices were computed. Index of Occurrence (10) is the ratio between the occurrence of the patterns during days with wind erosion and the occurrence during the entire wind erosion season. Index of Erosion Severity (IES) is computed by weighting the 10 with the area damaged by wind erosion associated with each pressure pattern. The IES identifies 2 pressure patterns that have significantly larger values than the other patterns. The most important is a pattern showing easterly flow over Scania, associated with 74 % (912 ha of 1235 ha) of the total damage in the study area. The second most important is a pattern showing westerly flow over Scania, associated with 5 % (63 ha) of the total damage. Both pressure patterns contain strong pressure gradients (in different directions) located over Scania. Depending on the location of the maximum gradient these patterns could be associated with wind erosion in other regions of north-western Europe.