Autumn and Extended Winter Daily Precipitation Variability over Central and Southern Scotland.

This paper analyses the main geographic patterns of rainfall variability over Central and Southern Scotland at the daily timescale during the autumn and extended winter (SONDJFM) period. Principal component analysis (PCA) is used to identify the most important rainfall patterns, with the first eight principal components (PC) accounting for 85.2% of the variance. The most important pattern (PC 1) is associated with a cyclonic W/SW flow and produces the wettest conditions in Renfrewshire and Dumbartonshire (PC 1); rainfall under the PC 1 pattern is widespread, with even the drier sites in eastern Scotland recording comparatively high totals. PC 2 produces wetter than average conditions in eastern Scotland (especially the Scottish Borders region) and so reduces the average rainfall gradient between the west (wetter) and the east (drier). All eight significant PCs are explained in terms of the atmospheric circulation and the geography of Scotland. Cluster analysis is then used to identify coherent rainfall regions. The regions on easterly days show the most difference from the other directions and the regions derived across all days. [ABSTRACT FROM AUTHOR]