Reconstructed Annual Precipitation Series for Scotland (1861 -- 1991): Spatial and Temporal Variations, and Links to the Atmospheric Circulation.

This paper constructs annual homogenised precipitation series for 13 locations in Scotland (1861–1991) from non-standard sources. Whilst the British Rainfall series represents the backbone of most UK rainfall records before the middle of the twentieth century, this paper returns to the original records to examine spatial and temporal variations in Scottish precipitation. The records were subjected to trend analysis and principal components analysis (PCA), and then related to atmospheric circulation parameters to understand the synoptic- scale mechanisms involved. Upward (downward) trends in precipitation were noted in western (eastern) Scotland over the period 1870–1991. Precipitation variability in western (eastern) Scotland is best explained by fluctuations in the westerly circulation (pressure), with the west- east precipitation gradient closing in those years with below average pressure, and a greater frequency of northerly and/or easterly winds. Precipitation trends cannot be explained by changes in atmospheric circulation patterns, suggesting that other factors must be involved. [ABSTRACT FROM AUTHOR]