Abstract : 1C.10
Climatic and synoptic analysis of the coldest air pools in Italy: First results

Massimiliano Fazzini, Bruno Renon, Paolo Pecoraro
Università di Ferrara - Dipartimento di Scienze della Terra

During the last decades, several new gauges have been installed at high altitude sites and valley bottoms, sheltered from direct sun radiation, within the Italian Alps and Apennines. The time series cover a few years but are characterised by extremely low temperature values. They were recorded in karst plateaus, punctuated by sinkholes and other morphologic depressions. Such morphologic features favour a strong nightly irradiance, especially when the ground is covered by snow. Among the coldest Italian sites we have the Asiago, Cansiglio and Lavarone plateaus in the Tridentine pre-Alps, the Fusine polje, next to the Slovenia and Austria borders and the headwaters of a few inner valleys (e.g.Visdende Valley in northern Veneto and higher Aosta Valley). In the central Apennines are worth to be mentioned Piani di Castelluccio, in the Sibillini mountains, and Piani delle Rocche in the Sirente Mountain massif. In such sites, annualy, less than – 30°C temperatures are recorded. Most of these sites are located at relatively low altitudes ranging from 1200 to 1500 m a.s.l. In this presentation, data for the range 2000-2006 of two coldest sites in Italy, Marcesina (1350 m a.s.l.) and Valmenera (905 m a.s.l.) plains are analysed. Absolute minimum values of –38°C and – 35°C, respectively, were recorded in March 2005. The extreme and mean values of these two stations were compared with those of neighbouring sites located at the same elevation but on mountain top or slope. In spite of a difference of as much as 10 °C in the lower values the average ones are, instead, very similar. Moreover, through the analysis of sea level and at 500 hPa geopotential meteorological maps and soundings, the synoptic conditions favourable to extreme low temperatures were pointed out. Recently, two other cold air pools were found, in the Ampezzo Dolomites and just north-west of Marcesina plain, where non certified recordings have shown temperatures markedly lower with absolute values around –45 °C.