A Long Relative Humidity Series for Armagh Observatory
Its relevance to the occurrence of 19th century potato famines in Ireland and atmospheric warming in the 20th century

C.J. Butler & A.M. García-Suárez

Figure 1. Time profiles of the mean seasonal and annual relative humidity at Armagh at 09.00 GMT

Introduction: John Tyndall first showed that water vapour played a major role in the radiative balance of the atmosphere, dwarfing the contributions of other greenhouse gases including carbon dioxide. It is surprising, therefore, how few studies of the long-term variability of atmospheric water content have been made. Though a relative humidity series, like all other meteorological series, is essentially local, it will contain elements of variability which derive from a wider region. It is in this context, we describe here some of the features of the Armagh RH series.

Data: Wet and dry bulb thermometer readings have been recorded daily at Armagh Observatory since 1838. Recently, these data has been corrected for instrumental error and changes in the time of reading to produce a homogeneous series covering all of the 20th and most of the 19th century. This is the longest such series in the world to be presented so far (Butler & García-Suárez, 2011).

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Last Revised: 2011 October 31st