Corrections of Systematic Errors, Data Homogenisation and Climatic Analysis of the Padova Pressure Series (1725-1999)

Abstract

A short history of the series with daily observations of barometric pressure in Padova (since 1725) is made, with special reference to the types of barometers used, their locations, the types of corrections (which were only partial in the early period), the calibrations and the comparison with primary instruments. The paper also describes the homogenisation of the series and the procedures used to fill the small gaps. The Padova series was compared with previously well investigated series from the ADVICE and IMPROVE projects and especially with the nearby Milan series in order to check its reliability. Trend analysis shows an increase in pressure (some 1 hPa) during the last a hundred year. This trend is a common feature for Northern Italy. An effect of the increased air pressure is a local lowering of the Northern Mediterranean Sea level by 1 cm. The part of the year mostly affected by this increase is from late spring to August and corresponds to an extension of the hot season, characterised by an earlier start, and longer duration of the Azores Anticyclone. This reduces the penetration of the Atlantic disturbances in the Northern Mediterranean and the precipitation associated with the passage of fronts. This change is associated with an increase in thermoconvective activity with thunderstorms and heavy precipitation. This explains why, in the last decades, the annual total amount of precipitation is slightly decreased and at the same time the frequency of intense rainfall is increased. Moreover, a comparison of the day-to-day pressure variability with the Western Mediterranean Oscillation (WeMO) indicates a significant positive correlation during the late autumn-early winter period. An increase of the WeMO index means a strengthening of the baric dipole from Azores to Northern Italy, that could be explained by a deepening of the cyclonic circulation over northern Italy from November to January.

Iberia winter rainfall trends based upon changes in teleconnection and circulation patterns

“…The WeMO was defined by MartinVide and Lopez-Bustins (2004, 2006 to account for those rainfall areas on the Iberian Peninsula which were not correlated with the NAOi. In addition, Camuffo et al (2006) recently used the WeMOi to compare it with variability in day-to-day pressure in Padova. In the study by Martin-Vide and Lopez-Bustins (2006), the WeMOi was shown to evolve in the opposite way to the AOi.…”

An automated sea breeze selection technique based on regional sea‐level pressure difference: WeMOi

“…The WeMO represents an alternative definition for the Mediterranean Oscillation (MO) (Conte et al, 1989), but is focussed upon the western Mediterranean basin. Some studies have already used daily data in different teleconnection pattern indices (Baldwin and Dunkerton, 2001;Beniston and Jungo, 2002;Camuffo et al, 2006;Martin-Vide and Lopez-Bustins, 2006). The application of the WeMOi for finding weak surface pressure gradients for the occurrence of sea breezes must be defined on a daily scale.…”

A collection of sub-daily pressure and temperature observations for the early instrumental period with a focus on the "year without a summer" 1816

“…However, observations made with mercury barometers need several corrections based on the characteristics of the barometer, on the variations in temperature and on the latitude (e.g. Moberg et al, 2002;Camuffo et al, 2006). Unfortunately, in most cases the historical observations were registered without any correction, and it is usually very difficult, if not impossible, to find any information about the barometer.…”