Precipitation related variables

Snow cover

 
 

Figure 30 - Days of snow cover each year for Scottish regions, from 1961/62 to 2004/05, with smoothed curves showing a running average.

Table 16 - Changes in days of snow cover (as a percentage), from 1961/62 to 2004/05. 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
Spring -28.0 -27.5 -44.6 -31.0
Autumn -70.9 -66.8 -82.6 -71.7
Winter -25.9 -31.8 -36.9 -30.2
Annual -28.8 -31.6 -40.7 -32.1

 

Please note, days of snow cover are calculated according to seasons rather than a full calendar year; they are calculated from September to the following May.

 

Regional trends

 

  • The number of days of snow cover has reduced in each region and in all seasons.
  • In winter, the decreases are greater than 25%, and are the largest changes (in terms of total number of days), a decrease of 7 days.
  • The largest percentage changes have taken place in spring and autumn, which shows that the snow season is getting shorter.
  • In autumn we can clearly see a downward trend with large reductions in each region greater than 70% in North and West Scotland.
  • The average number of days of snow cover in autumn is low, so even a large percentage change results in a relatively small reduction in the number of days.
  • In spring there are also large percentage decrease. However, the average number of days of snow cover in spring is greater than in autumn.

Spatial trends

 

  • The west of the country and particularly the western Highlands show the greatest reduction in snow cover in terms of the number of days. However, you should note that these areas are also those that normally have the largest number days of snow cover.
  • In some areas there has been an increase in the number of days of snow cover, particularly in northern mainland Scotland.

Future trends

 

  • The UKCIP02 report assesses snowfall in the future scenarios. We cannot directly compare this with the information we have on snow cover, but the general reduction is what the UKCIP02 scenarios suggest for the future.
  • Winter snowfall may reduce by 50% or more across Scotland by the 2080s (UKCIP02, medium high scenario).
  • The most obvious changes are over eastern Scotland, with a possible reduction of over 90%. However, the trends we have seen currently show a greater reduction in snow cover in West Scotland.

Figure 31 - Pattern of change in snow cover (in days) each year, from 1961 to 2004.