Atmospheric Pressure Anomalies Recorded on Italian Volcanoes: Possible Relationships With Solar Activity

Hourly data of atmospheric pressure are normally recorded in Italian active volcanoes (Etna, Vesuvius, Stromboli), for environmental and volcanic hazard monitoring purposes, in ground station networks managed by the Italian National Institute for Geophysics and Volcanology (INGV) and Vesuvius National Park. The common characteristic of the three networks is the presence of two stations, located the lower in the altitude range 0-300, the higher in the range 1000-1300 m, that in the cases of Vesuvius and Stromboli coincide with the top of the volcanoes. Data recorded during the years 2003-2004 have been first analyzed in order to looking for anomalies due to volcanic activities. The main result of the preliminary data analysis was the identification of two main anomalies, not directly linked to volcanic activity, occurred at the same time on the three volcanoes at least in two different episodes in the periods September-October, 2003 and July-August, 2004. The main characteristics of the anomalies was a decoupling of the signal recorded at sea level respect that one recorded at higher altitudes, evidenced by a dramatic lowering of the correlation coefficients calculated, on weekly basis, between the hourly values of atmospheric pressure. These anomalies appear to be strongly correlated with the level of solar activity, as determined by the values of the electromagnetic index Kp and of the Wolf number, the latter one calculated from the sunspot data daily acquired at the Catania Astrophysical Observatory of the Italian National Institute for Astrophysics.