It had happened with the storm Boris and it was also valid with the last flood: theAdriatic water which heats up and the Apennines which act as a shield against water vapor have a fundamental role in the frequency with which this type of event affects Emilia-Romagna. In mid-September theInstitute of Atmospheric and Climate Sciences of the Cnr talking about storm Boris and the cyclonic system that had moved fromNortheastern Europe to the Peninsula: “The amplification of the process of evaporationdue to the high temperatures of Adriatic Seafurther fueled the system, releasing large quantities of water vapor transported by the system into the atmosphere Mediterranean south towards the Adriatic”. A dynamic confirmed in an interview with The Republicyes Carlo Cacciamanithe meteorologist who heads the national agency ItalyMeteo and that he was at his house, a Bolognaduring the last storm. “We find ourselves between a warm sea, given the torrid summer, and an Apennines which hinders the flow of disturbances and triggers storms,” he told the newspaper. It should be remembered that in July the temperature of the Adriatic reached thirty degrees. Only then the Apennines hinder the flow of the disturbances. And the disaster remains entirely in Emilia-Romagna.
The Adriatic Sea like a steamer – A few weeks ago the Institute of Atmospheric and Climate Sciences of Cnr had explained the effects of the high temperatures of Mar Adriatictelling how the huge quantities of water vapor transported from the southern Mediterranean towards the Adriatic had favored instability, increasing theavailable energy. In fact, even before the arrival of the storm, i meteorology they had pointed out that the temperature of the Adriatic Sea was still around 25 degrees, a rather high value considering the characteristics of the cyclone. And predicting a thermal contrast of 45 degrees at 5 thousand meters which could have generated extreme phenomena. Without snowfallthe water from the rains would have done the rest, helping to swell the rivers. What happened in the past few days? According to the meteorologist Mattia Gussonof the Department of Earth Science of the University of Turin, “la storm perfect: on one side the sea is still quite warm, on the other the descent of unstable and cold currents from Northern Europe”. “The Adriatic Sea – he explained to Corriere della Sera – has become a steam generator, capable of evaporating tons of water” which then falls like rain in Emilia Romagna (but also in Liguriain Tuscany, on Sicily) like a real universal flood.” In the province of Bologna alone, between 150 and 200 millimeters of rain fell in 24 hours, “as much as usually falls in two months of precipitation”.
The shield of the mountains – But there is another element that contributes to making these precipitation particularly dangerous for Emilia-Romagna. It is theApennineswhich blocks the precipitationmaking them always fall into the same areas. “Is called Stau effect – explains Gussoni – and is generated every time the atmospheric currents impact perpendicularly against a relief. The air, forced to rise along the slope of the mountain will cool down and this cooling will favor the first saturation of the air, then the condensation of water vapor excess”. A bit like what also happens in other regions, such as Tuscany and Liguria.
