Abstract : 1C.2
On the continuity and climatic variability of the meteorological stations in Turin, Asti, Vercelli and Oropa (Piedmont, Italy)

Fiorella Acquaotta, Claudio Cassardo, Roberto Cremonini, Simona Fratianni
Department of Earth Science, University of Turin

This work analyses the series of the maximal/minimal temperatures and the precipitations in the period from 1951 to 2003. Measurements extract from the meteorological stations of National Hydrographic Service of the cities of Turin, Asti, Vercelli and Oropa. The daily series between 1990 and 2003 have been compared one to one (Biancotti et Mercalli, 1990) with the series from ARPA*-Piedmontís stations located in the same cities in order to assess how similar they are. Due to the good accordance between the sources, some missing values in a series can be replaced with the data from the other one, or, it can be accurately predicted the expected discontinuity gap. To optimize the comparison of the data, for each year and both the series, the values missing in at least one series have been neglected, then the monthly, seasonally and annually values have been computed by holding the 80% of the data, according to European Climate Assessment (Tank et al., 2002). Statistical tests have been applied to the new series for evaluating the distribution and the average of the measurements. For the series of the temperatures the differences between the maximal and minimal temperatures logged by the instruments have been calculated and, for each year, the gaps out of a certain range have been observed. Regarding the precipitations, annual ratios have been highlighted between amounts of rain and the difference of the numbers of raining days and the high intensity days. No common characteristics came out from the comparison but this highlighted some discontinuities inside the series. For each 53 year series a historical investigation has been performed and the homogeneity degree evaluated according to the Standard Normal Homogeneity Test (SNHT) (Alexandersson et Moberg, 1997), which in some cases showed as discontinuity points the same years highlighted by the direct comparison. After homogenizing the series, the trends and climatic analysis have been calculated.