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Ann. Geophys., 23, 1987-1995, 2005
www.ann-geophys.net/23/1987/2005/
© European Geosciences Union 2005
Further signatures of long-term changes in atmospheric electrical parameters observed in Europe
F. Märcz1 and R. G. Harrison2
1Geodetic and Geophysical Research Institute of the Hungarian Academy of Sciences, H-9401 Sopron, POB 5, Hungary
2Department of Meteorology, The University of Reading, P.O. Box 243, Earley Gate, Reading, Berks RG6 6BB, UK
Abstract. Long-term decreases found recently in both the atmospheric electrical
potential gradient (PG) and the air-Earth current density (Jz), using
observation series from the UK and Hungary, have motivated studies of other
European data. Two surface data series somewhat longer than a decade were
available: PG data obtained at Serra do Pilar (Portugal), and PG, Jz and
positive air conductivity measurements at Athens (Greece). Selecting data to
minimise local effects, the 1960–1971 Serra do Pilar PG values decrease at
dawn and in the evening. Dawn data obtained at Athens (1967–1977) indicate a
reduction in Jz, while the simultaneous PG values there increase
(coincident air conductivity values decrease) for the periods investigated.
The Athens PG increase is attributed to local aerosol influences, typical of
urban environments. Despite the urban influence, the Athens Jz shows
similarities with soundings of the ionospheric potential. The decline in
Jz at Athens occurs simultaneously with a decrease reported previously
in Jz at Kew (UK), indicating that, at least, a regional decrease in the
global atmospheric electrical circuit occurred during part of the twentieth
century. Similar surface changes occur in European atmospheric electrical
parameters, with a decrease of about 0.5% to 0.7% per year between
1920 and 1970 (possibly extending back to 1898), an annual decrease of
between 2.7 and 3.4%, between 1959 and 1971 and a continued decrease of
about ~1% per year between 1967 and 1984, possibly still
continuing.
Keywords. Meteorology and atmospheric dynamics (Atmospheric
electricity) – Geomagnetism and paleomagnetism
(Time variations, secular and long term) – Atmospheric composition
and structure (Aerosols and particles)
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