The Archives of Armagh Observatory

Three independent mean temperature series for Armagh Observatory, covering the period 1796-2002 have been calibrated and corrected for the time of reading and exposure. Agreement between the three series is good in regions of overlap. With a short gap in the Armagh data from 1825 to 1833 filled by data from two stations in Dublin, the resulting series is the longest for the island of Ireland and one of the longest for any single site in the British Isles.Over the past 207 years, we note that temperatures in Armagh, in all seasons, show a gradual overall trend upwards. However, there are seasonal differences: summer and spring temperatures have increased by only half as much as those in autumn and winter. This is partly due to the exceptionally cold winters and autumns experienced prior to 1820. Relative to the overall trend, warm periods occurred in Ireland, as in other parts of Europe, in the mid-19th century, in the mid-20th century and at the end of the 20th century. Relatively cool temperatures prevailed in the early 19th century, in the 1880s and in the 1970s. Thus, if the baseline against which current temperatures are compared were moved from the late 19th century to include the earlier warm period, the apparent warming at the end of the late 20th century would be correspondingly reduced.A gradual decline in the daily temperature range at Armagh since 1844 may have resulted from higher minimum temperatures associated with increased cloudiness.A 7.8 year periodicity is identified in winter and spring mean temperatures at Armagh, which is probably a consequence of the North Atlantic oscillation.

Section: Instrumental Correctionmentioning

confidence: 75%

Section: Cyclic Analysis Of Armagh Temperaturesmentioning

confidence: 95%

Section: Correction For Time Of Readingmentioning

confidence: 99%

Section: Correction For Exposurementioning

confidence: 99%

See 2 more Smart Citations

Air temperatures at Armagh Observatory, Northern Ireland, from 1796 to 2002

Butler

Suarez

Coughlin

et al. 2005

“…The Armagh Observatory data were taken from the Observatory Archives (Butler and Hoskin, 1987) and the data for the three stations in the Republic of Ireland were kindly provided by the Meteorological Office, Dublin.…”

Section: Introductionmentioning

confidence: 99%

Sunshine records from Ireland: cloud factors and possible links to solar activity and cosmic rays

Πάλλη¹,

Butler²

2001

The records of sunshine hours obtained since the late 19th century from four stations distributed throughout Ireland were analysed. A gradual decrease in sunshine hours has occurred at all four sites since records began. Increasing cloud factors, resulting from enhanced evaporation rates over the Atlantic as sea surface temperatures have risen, is one possible explanation for the decline in sunshine.A strong negative correlation was confirmed between sunshine factors from ground-based observations and satellite-based cloud factors over Ireland. In addition, it was found that cloud factors over Ireland correlated well with cloud factors over large oceanic areas such as the North Atlantic and mid-high latitudes generally. Thus cloud factors (and similarly sunshine factors) from regions on the boundaries of large oceans which lie in the direction of the prevailing wind could be useful in determining the long-term changes in cloud factors over more extended areas. Knowledge of such long term variability in the Earth's cloud cover is important input information for modelling past climate change.The importance of cosmic rays as a link between solar activity and climate was assessed from a study of the ISCCP-D2 satellite cloud factors and Irish sunshine data. Whilst these results confirmed the strong correlation between total cloud factor and cosmic rays over non-tropical oceans between 1984 and 1991 previously reported, it was found that this correlation did not hold in the subsequent period 1991 -1994. Other work has established a link through specifically low cloud.Indirect evidence of cloud formation by cosmic rays from a variation in the sunshine factor following Forbush decreases, and over the sunspot cycle, was mostly negative. Although a dip at seven years past sunspot minimum is evident in the sunshine factor for all four sites and in most seasons, it is of marginal statistical significance. Copyright

Relative humidity at Armagh Observatory, 1838–2008

Butler¹,

García-Suárez²

2011

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 significant anti-correlation between RH and northerly winds.Two conspicuous peaks in RH during the 19th century coincide with major infestations of potato blight in Ireland.