Recent abatement of easterly winds in the northern Adriatic

Abstract

Easterly winds from the northern Adriatic contribute, together with atmospheric depressions, and the often decisive southerly winds from the southern and middle Adriatic, to produce damaging sea surges in the Gulf of Venice. A new statistical analysis of 3-hourly wind records from Trieste for the period 1951–1996, has shown a clear decline in the frequency and strength of Bora and other easterlies. This abatement is not accompanied by a strengthening of winds from other directions, but by more frequent calm situations (from 26% of total observations in the 1950s, to 44% during the last 10 years, and even to over 60% during the early 1980s). Similar (although weaker) declining trends for the easterlies have been recorded at other stations in the northern Adriatic (Ronchi, Venice). An inspection of previously published data from Trieste suggests that such trends may have been going on, possibly with minor fluctuations, since at least the beginning of regular instrumental records, in the late 1860s. Such changes in wind pattern, which have favourable effects on the frequency of coastal flooding, may be due, at least in part, to interdecadal climate variability. However, the persistence of certain trends suggests a climatic shift, with, in particular, less-frequent situations, with strong atmospheric pressure gradients between highs in central/eastern Europe and lows in southern Italy or in the Adriatic area. Such situations may be a consequence of recent global warming and of less-frequent drifts of polar cold air towards middle latitudes. Copyright © 1999 Royal Meteorological Society