Description of the Problem

The city of Milan is situated in the central-western area of the Po Valley. The area is surrounded by Brianza hills on the northern side and plains on the other three sides. The topography is quite simple, with an average altitude of 100 m. The altitude sharply increases as it extends north beyond Brianza hills until reaching the Alps, over 3,000 m high and only 200 km from Milan.

Milan has a typical continental climate. Generally winters are quite cold and foggy and summers warm and humid; autumn and spring are characterised by highly changeable weather conditions with more frequent precipitation in September and October.

The Alps and Apennines that surround the Po Valley form the physical barriers that protect the area from the major circulations coming from Europe and the Mediterranean.

The presence of a large, densely urbanised centre has, as is well known, a considerable influence on microclimatic conditions, both in terms of temperature and wind fields. The examination of measured data in Milan points out a typical effect of metropolitan areas, the so-called "heat island" phenomenon, due to different anthropogenic causes such as multiple reflection between vertical walls of buildings, the turbulence caused by buildings, the production of energy generated by industry, heating plants, etc.

Moreover, the presence of the large, densely populated centre determines marked deviations in prevailing winds entering the city. The analysis of wind direction measured at different monitoring stations in the city shows that the degree of deviation from the original direction depends on the location of the station and on the developing direction, with a tendency to rotate in a counter-clockwise direction in relation to the city centre.

The Italian laws in the environmental field don’t include specific rules to protect climate on the local scale; in fact, its protection is indirectly committed to air quality legislation, which is generally focused on emissions and emissions control.