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Accepted for publication in the International Journal of Climatology Relative Humidity at Armagh Observatory, 1838-2008

Summary: Accepted for publication in the International Journal of Climatology
Relative Humidity at Armagh Observatory, 1838-2008
C.J. Butler and A. M. García-Suárez
Armagh Observatory, College Hill, Armagh BT61 9DG, N. Ireland
Short title: Relative Humidity at Armagh Observatory
Abstract: We present a calibrated atmospheric humidity series for Armagh
Observatory, Northern Ireland. Beginning in 1838 and continuing to the present
day, this series is believed to be the longest presented so far. Daily wet-bulb and
dry-bulb temperature readings are corrected for the time of reading and for
known instrumental errors to determine mean monthly, seasonal and annual
relative humidity (RH) at 09:00 GMT from 1838 to 2008 and at 21:00 GMT from
1844 to 1964.
The mean seasonal and annual time series of RH at this site show only marginal
evidence for a trend in RH since the 1880s, however there is significant decadal
and multi-decadal variability, some of which appears to be cyclic. Wavelet
analysis indicates the presence of two quasi-periodic components in RH, one
ranging from 23.4 to 25.5 years and the other from 36 to 51 years. We discuss
potential physical origins of these cycles such as changes in the atmospheric and
thermohaline circulation and the solar magnetic cycle. There is a small but


Source: Armagh Observatory


Collections: Physics