Reconstruction of long-term precipitation records for Edinburgh: an examination of the mechanisms responsible for temporal variability in precipitation

Recent dry years (combined dry winter and summer months) within the UK (2005 and 2006) have enhanced concerns relating to long term water resources and future water provision in large conurbations. This paper examines the mechanisms responsible for precipitation variability for five different areas in Edinburgh (precipitation regions) using composite historic precipitation records for the period 1861-2005. Trend analysis and principal component analysis (PCA) were undertaken to examine precipitation variability over time and space. Annual correlation co-efficients were derived for relationships between precipitation areas, atmospheric-oceanographic variations and geographic parameters. Stepwise regression models were constructed to specify annual precipitation, through atmospheric variations, for each of the precipitation areas. Significant downward trends in precipitation (p <0.05) were noted in two out of the five precipitation areas, with one principal component representing precipitation variability over Edinburgh and the Pentland Hills. Precipitation variability is best explained by fluctuations in pressure, altitude and proximity to coast. Precipitation trends cannot be explained by changes in atmospheric circulation patterns.