Predictability of northern Adriatic winter conditions

Presented results indicate that a long-term (several months ahead) forecast of the winter northern Adriatic conditions is possible and that it can be based on the analysis of meteorological conditions and geostrophic circulation fields of the previous autumn. Using 1981-2007 February data we show that in winters of the type A, salinity in the northern Adriatic is lower and production of phytoplankton higher than in the B type winters. This indicates that the impact of the Po River waters on the northern Adriatic is more pronounced during the A type winters. The two types, A and B, have already been identified on the basis of the bottom density differences between eastern and western part of the northern Adriatic but more precise definition is given here. Based on the data collected during hydrographic cruises in 2000 (type B conditions) and 2001 (type A conditions), we found that the two winters differed in geostrophic circulation patterns as well. Eastward of the Po River delta there was a large cyclonic gyre in 2000 and a large anticyclonic gyre in 2001. Circulation patterns were highly dependent on autumn conditions, with bottom density changes as the most likely triggering cause. Strong surface heat losses and many bora episodes preceded the winter of 2000, while moderate cooling and sirocco events preceded the winter of 2001.

► There are A and B types of northern Adriatic winter conditions. ► In winters of type A waters of Po River are drawn offshore, into northern Adriatic. ► In winters of type B waters of Po River stay close to the coast. ► Forecast of A and B conditions seems to be possible several months in advance.