The Italian air force sea level pressure data set (1951-2000).

A set of 39 homogenised sea level pressure records, extracted from the Italian Air Force dataset (1951-2000), is introduced and analysed for trends. The data consist of 3-hourly observations. Daily mean pressures are obtained using a method that allows biases to be avoided due to the presence of a high fraction of days that do not have all 8 observations. Trend analysis is performed on seasonal and yearly basis and concerns both the individual station records and the series of their averages. The results show a highly significant positive trend in winter and yearly air pressure all over Italy. It is mainly due to a change-point around 1980. The Italian air pressure records are also compared with the NCAR/NCEP and UKMO gridded data sets. The results give evidence that gridded data capture most of the trend and variability of air pressure over Italy, even if NCAR/NCEP data display some significant inhomogeneities with respect to the station records.