Summary: PRECIPITATION AT ARMAGH
C.J. Butler, A.D.S. Coughlin and D.T. Fee
The meteorological series maintained at Armagh Observatory began in 1795 and are the longest
in Ireland and among the longest in the British Isles. Here we present the monthly mean daily
precipitation recorded at Armagh since 1838. Variations in the distribution of the rainfall during
the year, over this period, are apparent, with a tendency for drier summers in recent decades. We
find a significant correlation between the mean seasonal rainfall and the North Atlantic Oscillation
index during autumn and winter, and there appears to be a negative correlation between the
summer rainfall and the North Atlantic Oscillation index for the previous winter. A search for
periodicities has been made and no evidence of an eleven-year cycle similar to the Sunspot cycle
has been found. However, Fourier analysis reveals an approximate seven-year cycle in summer
rainfall. We examine the evidence that this cycle may be linked either to the Taurid meteor
stream or to the North Atlantic Oscillation.
C.J. Butler, A.D.S.
Coughlin and D.T.
College Hill, Armagh