Statistics of the seasonal cycle of the 1951 - 2000 temperature records in Italy and in the Mediterranean area ( ∗ )

— We present an analysis of the seasonal cycle of the last 50 years of records of surface temperature in Italy, as described by observations of maximum and minimum daily temperature, and of the surface and upper air temperature of the whole Mediterranean area, as described by the 1951-2000 NCEP reanalysis. We compute the best estimate of the seasonal cycle of the variables considered by adopting the cyclograms’ technique. In the case of the Italian surface temperature, we observe that in general the minimum temperature cycle lags behind the maximum temperature cycle, and that the cycles of the Southern Italy temperatures records lag behind the corresponding cycles referring to Northern Italy. In the case of the NCEP reanalysis data for the whole Mediterranean area, we observe that at surface the phase and amplitude of the seasonal cycle are strongly characterized by the signature of the underlying surface, while in the upper air large-scale features related to ocean-continent contrast come into play. All seasonal cycles lag considerably behind the solar cycle. In all cases considered, the amplitude and phase of the seasonal cycles do not show any statistically significant trend in the time interval considered. This works supports the idea that climate change studies are much more reliable when upper air data are taken into account.