Recent abatement of easterly winds in the northern Adriatic

Easterly winds from the northern Adriatic contribute, together with atmosph eric 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 pe riod 1951-1996, has shown a clear decline in the frequency and strength of Bora and other easterlies. This abatement is not accompanied by a strengthe ning of winds from other directions, but by more frequent calm situations ( from 26% of total observations in the 19509, to 44% during the last 10 year s, 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 publis hed data from Trieste suggests that such trends may have been going on, pos sibly with minor fluctuations, since at least the beginning of regular inst rumental records, in the late 18608. Such changes in wind pattern, which ha ve favourable effects on the frequency of coastal flooding, may be due, at least in part, to interdecadal climate variability. However, the persistenc e of certain trends suggests a climatic shift, with, in particular, less-fr equent situations, with strong atmospheric pressure gradients between highs in central/eastern Europe and lows in southern Italy or in the Adriatic ar ea. Such situations may be a consequence of recent global warming and of le ss-frequent drifts of polar cold air towards middle latitudes. Copyright (C ) 1999 Royal Meteorological Society.