Background Many environmental and energy studies need meteorological data in order to run models for analysis and forecasting. For example, meteorological data is required for dynamic simulation analyses and for models predicting the dispersion of pollutants in the atmosphere. Analysis of the dispersion of pollutants in the atmosphere over a long period is generally carried out using statistical tables, derived from a multi-year data set. However, the results of recent studies have not been reliable. In Italy, the national meteorological data-set dates back to the 1970s and needs to be updated. However, one of the main problems is the lack of an approved standard of data collection, which often reduces data significance. Objectives The ET IDEA project aimed to develop and test the typical reference years (TRYs) concept as an innovative tool for the reconstruction, standardisation and analysis of meteorological data for the whole Italian territory. The project’s main expected output was a software package containing TRYs for 1 500-2 000 locations across Italy. The software would facilitate the standardisation of meteorological data and analysis for the whole territory. It would be relevant for the following environmental and energy applications: - Environmental monitoring TRY, for evaluating pollutant dispersion in the atmosphere; - Wind TRY, for analysing the dynamic performance of wind-power plants; - Photovoltaic TRY, for registering the dynamic performance of photovoltaic plants; and - TRY for predicting the dynamic performance of solar-thermal plants and calculating the winter and summer energy load of buildings. Project's objectives included the development of new methods for identifying and completing missing meteorological data, calculating solar radiation from other variables and the development of a method for expanding the meteorological data across wider geographical areas. Results First, the project identified all the meteorological stations in Italy and the companies that own and administrate them. In Italy, meteorological stations are owned and managed by different public and private companies, and as a result, they often lack a common standard for data recording and validation. At the end of the project, 2 697 meteorological stations, located in the different Italian regions, had been mapped and meteorological data from 1 471 of these stations had been acquired and imported into a specific database. In order to process this information, the project devised an algorithm to automate the selection of the suitable meteorological stations. Quality control of the raw data was carried out to avoid inconsistencies and mistakes in the measurements. Whenever possible, missing meteorological values were filled in using a ‘reconstruction’ process. Three statistical methods were studied and developed: an interpolation for the reconstruction of missing values up to five consecutive hours; a linear interpolation inn 6-24 hour gaps, and a ‘long’ linear interpolation for 25-72 hour gaps. The project also applied algorithm for automating the selection of the suitable meteorological stations: this allowed data to be imported into a specific database automatically. Finally, four more algorithms were designed and validated for the generation of four types of TRYs: the ‘Thermal TRY’, the ‘Photovoltaic TRY’, the ‘Eolian TRY’, and the ‘Environmental TRY’. More than a thousand TRYs were then generated from the meteorological data of about 600 meteorological stations. The TRY database is available online at http://www.itmeteodata.com/. Additional complete databases in other EU countries can by created by using the project’s methodology for the development of new typologies of TRYs. A single European database supporting environmental European policies could one day be a reality. Further information on the project can be found in the project's layman report and After-LIFE Communication Plan (see "Read more" section).