Precipitation related variables

Average rainfall intensity


Figure 36 - Average rainfall intensity on days with 1mm or more of rain (in millimetres a day) for
Scottish regions, from 1961 to 2004, with smoothed curves showing a running average.

Table 19 - Changes in average rainfall intensity on days with 1mm or more of rain (as a percentage), from 1961 to 2004. Values in bold show that we are 95% confident (statistically) that the change is part of a measurable trend.


North Scotland East Scotland West Scotland Scotland
Rainfall intensity (%) 7.4 7.6 7.8 7.6


Regional trends


  • There is a trend of increasing rainfall intensity in both East and West Scotland.
  • There is a similar size of increase in North Scotland but this does not appear to be part of a trend, probably because natural variability in rainfall is higher in this region.
  • There does not appear to be a strong link between year-to-year rainfall intensity over the three regions, although the long-term trend (smoothed curve) is very similar.

Spatial trends


  • There is an increase for most of Scotland although there is a reduction for some northern and coastal areas, including the Outer Hebrides, Orkney and Shetland Islands.

Future trends


  • It is very likely that the intensity of rainfall will increase in winter months.
  • An east-west contrast in change is estimated in the UKCIP02 scenarios, with the most extreme changes taking place in eastern Scotland. This geographical contrast is clear in each of the UKCIP02 scenarios.
  • However, we have not seen this pattern when analysing the intensity of heavy rainfall we have seen since 1961, although we cannot directly compare the measures we have used with those used in the UKCIP02 report.

Figure 37 - Pattern of change (as a percentage) in rainfall intensity each year on days with 1mm or more of rain, from 1961 to 2004.