How much does it rain in Italy? The answer in a study by UniMilano and CNR
The availability of an adequate level of water resources is a matter of great relevance and importance, involving a wide range of sectors, including agriculture and energy. It is therefore essential to understand in detail the precipitation distribution on the Italian territory.
To respond to this need, the University of Milan and the National Research Council – CNR have developed a well-structured research programme to determine how much it rains on average on each point of the Italian territory (the term “point” refers to a grid cell corresponding to less than 30 arc-seconds of longitude and latitude, or an area of significantly less than one square kilometre). The results of the study have been published in the International Journal of Climatology.
The study, whose first author is Alice Crespi, a young PhD student in Environmental Science at the University of Milan, as well as presenting the annual and seasonal precipitation distribution across the country, also provides a significant methodological contribution as it analyses the potential and limits of the models needed to estimate the precipitation rate of such a high number of points (about 500,000), obtained from a much smaller number of observation stations (about 5,000).
The numeric fields produced, available for each month of the year, refer to the period 1961-1990, the last period for which the data from the national mechanical station network is available with a certain continuity. This data, however, can be easily updated by using a method known as anomaly detection method. This method is based on the fact that the temporal signal of a meteorological variable has a much simpler spatial structure than its mean value and can, therefore, be captured even by a fairly small number of stations.
It is therefore easy to overlap the spatial precipitation distribution of the period 1961-1990 with a corresponding spatial distribution that describes the relative changes compared to this thirty-year period to obtain the spatial precipitation distribution each period of interest.