Characterisation of Emilia-Romagna region in relation with late frost risk

Abstract

This paper describes a topoclimatic analysis that was carried out during the first year of the DIsGELO project. A climatological study and an orographical analysis were carried out, in order to identify frost-prone areas in Emilia-Romagna region (Italy). The former was used to identify and characterise the frost events in the period March–April 1987–2000 for 161 meteorological stations. A synthetic frost risk index, taking into account both temperatures and phenological conditions (expressed by decade number) was devised. For every station we computed both the synthetic frost risk index and the mean minimum temperature. The analysis of the digital elevation model provided some orographical variables: slope, aspect, absolute and relative altitude above valley bottom, valley width, closeness to the sea, and new variables specifically devised to evaluate surface roughness in the plain areas. Maps were then created for every variable and values were obtained for every station by means of a geographic information system. The study area was divided into two domains, the hill zone and the plain, and for each the correlation between the climatological and orographical variables was computed and geostatistical techniques were applied to create some temperature and frost risk climatological maps. For the hills of Emilia-Romagna, a significant correlation was found between the mean minimum temperature during frost events and two orographical factors: the relative altitude above the valley bottom and the closeness to the sea. For the plain no significant correlation was found up to now, probably due to the insufficient detail in the data, so some arbitrary coefficients, based on former practical experience, were added in order to take into account two other orographical factors describing the presence of hollows and knolls. An exponential relationship between the mean minimum temperature and the synthetic frost index was then used to obtain a preliminary frost risk map.