The climate of Rome and its action on monument decay

The 3-hourly standard meteorological data measured at Rome for the period 1951-1996 were analysed in order to gather information about the impact of climate on monument decay. The freezing-thawing and condensation-evaporation cycles in micropores were computed for each month. The occurrence of the freezing-thawing cycles was determined by means of a cross comparison between the temperature observations and the model calculations for the lowering of the freezing point due to the curvature effect of the ice surface into pores. The occurrence of the condensation-evaporation cycles was determined by means of a cross comparison between relative humidity observations and the lowering of the critical relative humidity for condensation into micropores due to the curvature of the water meniscus. The effect of sea spray on the lowering of the freezing point was calculated to evaluate the number of the freezing-thawing cycles on the surface or in the macropores contaminated by NaCl. Wind roses as well as the drizzle, rain, shower, hail, snow and fog roses were drawn in order to determine which vertical-surface orientations undergo wetting or washing out by meteoric water. Finally, the relevance of each of these meteorological variables was evaluated, evidencing the peculiarities of the region, which is influenced by both the Mediterranean climate and the cyclonic systems coming from the Atlantic Ocean.