In recent decades the interest for climate variability and extreme climate events has increased. The assessment of meteo-climatic impacts on environment, human health, socio-economic and urban systems is of great importance. Higher information needs on the issue has favored the development of statistical frameworks by international institutions to provide standardized and harmonized methodologies for producing data and indicators.
Climatic variability and extreme events of temperature and precipitation have visible consequences also in urban context, characterized by concentration of population and infrastructures. In the last two decades many Italian cities recorded relevant impacts due to climatic variability and extreme events occurrence. An increasing variability is forecast by climatic model (IPPC). Climatic extreme events as heavy rains, floods, long periods without rains, temperature that remains high for days and nights, heat waves, decrease in the number of cold days pose a threat to human health and safety of Italian cities. In fact, such events may damage infrastructures as well as artistic and cultural heritage, may also hamper economic activities and provision of public utilities (water, energy, transport).
The Istat Meteo-climatic and hydrological data survey (edition 2017) has the aim to update the existing database on meteorological and hydrological data (time series 1971-2016). The survey is included in the National Statistical Program (cod. IST-02190) and is regularly conducted. Statistical information provided by this survey can be put in relation with other official statistics regularly produced by Istat on thematic areas such as environment, human health, urban systems, public utilities, to multidimensional analyses.
Meteo-climatic variables collected include daily observations of precipitation (mm), minimum temperature (Celsius degree), maximum temperature, mean temperature, and humidity. As far as 21 Italian Regional Capital Municipalities are concerned – where 38.9% of Italian population lives – measurements come from 122 meteorological gauging stations (units of analysis) located within the territory of such cities. Survey units are represented by 65 institutions (public and private) and agencies officially managing national networks of georeferenced meteorological stations. Quality controls, considering the long time series of daily data, lead to a reduced sample of 43 stations, located in all Regional Capital Municipalities. Based on this data collection, meteo-climatic conditions in the main cities are analyzed.
Istat Statistical Report describes aspects of Regional Capital Municipalities climatic variability, in particular observing anomalies of temperature and precipitation comparing the 2002-2016 mean values with the Climatic Normal (CLINO) value, defined by the 1971-2000 period. Some Indices of climatic extremes, defined by the ETCCDI (Expert Team on Climate Change Detection and Indices of WMO-UN) core set, have been calculated for Italian Regional Municipalities.
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