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Potential changes to snowfall in Snowdonia

Objectives: The Countryside Council for Wales developed this mock case study (using dummy data) to obtain location-specific information to explore the potential altitudinal changes in snowfall in the Snowdonia area under climate change.

How they used UKCP09 dummy data

1. In order to cut down on resource requirements it was decided to use one Weather Generator grid square. Although the Weather Generator incorporates altitudinal information, an approach was taken to calibrate one Weather Generator grid square output for altitude based on observed.

2. Meteorological observations were only available at 500 m and sea level (0 m) for the areas in question. From those stations, the lapse rate of 0.6°C/100 m was determined in order to scale to different altitudes (Snowdonia is 1085 m high). Additionally, a correction for the fact that it often rains at altitude in the mountains when it does not at the coast was incorporated.

3. The Weather Generator was run for one grid square 100 times for the baseline and the future to produce hourly data for both 30-year time periods.

4. This data was then scaled to altitudes of 500 to 1000 m at 100 m intervals using the lapse rate and correction factor for rainfall determined through analysis of observed data.

5. The occurrence of precipitation and temperature less than 0°C was used to estimate snow cover during the day at different altitudes for both the baseline and the future. The hourly approach was taken to avoid overestimating the amount of snowfall in one day by using daily minima.

Next steps

This approach could be used to assess the annual altitudinal extent of snow cover and more emissions scenarios and time periods could be assessed. Outputs from the analysis could be shared as a Welsh climate change indicator through reports. Additionally, summary messages to communicate the climate change message to the wider public could be disseminated through the website, press releases and associated media communications.

Lessons learned

  • Investigating environmental (and especially biological) thresholds for Snowdonia illustrated their complexity, and the limitations in using scenario data to examine impacts on the thresholds. Even the simpler, physical snowfall threshold required hourly temperature data.
  • The use of the Weather Generator requires significant caveats to be conveyed so that they are very clearly seen as broad climatological projections rather than hourly or daily forecasts for the future. 

Find out more

  • Contact details: Clive Walmsley, Countryside Council for Wales