Soil temperatures at Armagh Observatory, Northern Ireland, from 1904 to 2002

Soil temperatures at 30 and 100-cm depth from Armagh Observatory covering the period 1904–2002 are presented. The series has been corrected for changes in depth and location of the thermometers and has been compared with data from two other sites in Ireland: Birr and Valentia. Linear regressions of the soil temperatures over the past century for the three sites have positive slopes in all seasons which vary from 0.04 to 0.25 °C/decade, depending on the season, depth and location. There appear to be some geographical differences, with relatively shallow trends in winter in Armagh and Birr and steeper trends in Valentia. Soil temperature variations at the Armagh Observatory are intimately related to changes in the mean air temperature but are also influenced by changes in precipitation. We show that winter soil temperatures at Armagh can be successfully reconstructed from air temperature records.