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Great interest has been shown in the installation of an automatic weather station on Snowdon summit at 1085 metres in North Wales. Until recently, there had been no high elevation automatic weather stations in Snowdonia. Yet the need for this information for mountain safety, weather forecasting, public information, research and teaching is considerable.

The weather station project was initiated in 1989 in response to the need for a long-term study of climate and environment in mountain regions. The Snowdon summit weather station immediately sparked a demand for live public information to help walkers and climbers judge the mountain-top conditions. The first semi-automatic weather-station was installed on Snowdon summit the winter of 1993. It is unique in Britain, being the only non-mains powered, radio-linked mountain-top weather-station. This initiative was led by Dr Jeremy Williams at the University of Wales, Bangor with considerable assistance from the Meteorological Office, sensor manufacturers and sponsors. The equipment has worked effectively over some of the harshest winters in the last 15 years and, recently, over the hottest summers on record.

During the summer of 1995, the first public displays of Snowdon summit weather conditions went live. These computer-based displays dialled the summit each hour and provided a continuous summary of summit conditions displaying air temperature, average and gust wind speeds, wind direction and hourly rainfall. These displays were used in Llanberis, Betws y Coed and at Pen y Pass to enable walkers and climbers to check summit conditions before setting out on the mountain. The summit equipment is solar-powered and the data being relayed by a cell-phone link.

Summit weather conditions are recorded continuously, and summarised for every hour, 24-hours each day, every day of each year. Summit winds gusting to 140mph have been recorded, summit temperatures drop below -10°C over the winters and rise to over 25°C in the better summers. Rainfall averages between 2500mm and 3000mm each year. The Met. Office have now included Snowdon in their network of SIESAWS sites (Severe Icing Environment Semi-Automatic Weather-Station).

Snowdon is a difficult site in many ways. Being close to the coast, it receives the full force of prevailing south-westerly gales. The area is also well-known for its high level of rainfall. Rime ice forms quickly and copiously under certain winter conditions; on many winter days, everything on the summit can be coated with over 300mm of rime. This can cause some instruments to stop working. Solutions to this problem and trials of novel ice-resisting wind sensors manufactured by Vector Instruments in North Wales are still under way.

The weather-station has a cellphone and radio link to the Met. Office and the University of Wales, Bangor to collect summit weather data each hour. From 1995, this information has been fed into the Met. Office data network for use in weather forecasting and climate monitoring. The Met. Office has comprehensive facilities for disseminating summit weather conditions: television and radio, weather centres and telephone and fax services.

The Snowdonia Weather-Stations Project has several objectives:

One of the characteristics of weather in Snowdonia is its variability. There are now three weather stations: the lakeside in Llanberis at 105m, Clogwyn Station at 770m and Snowdon summit at 1085m providing free information to the public.

The spate of accidents involving walkers and mountaineers in the Welsh and Scottish mountains each winter has re-affirmed the need for more information about mountain summit conditions. Since 1995, weather information from Snowdon has been available through existing well-established sources such as the Met. Office services and Snowdonia National Park Wardens. Through collaboration with First Hydro in 1999 the display and dissemination of Snowdon weather information at First Hydro's Visitor Centre, Electric Mountain in Llanberis enables thousands of visitors to understand and take an interest in environmental monitoring work and its importance in Snowdonia. At Electric Mountain you can see the weather and climate sensors close-up and relate them to the live display inside the building.

The mountains of Snowdonia form a protected environment. Little, however, was known about some elements of the weather on the mountains; almost nothing was known, for example, about winter conditions in the mountains. The monitoring and understanding of mountain environments is a high profile activity in response to their global, regional and local importance identified at Rio in Agenda 21. The general public and the environmental and research communities now see mountains as essential and fragile areas providing water, diverse ecological habitats, refuges for rare flora and fauna, and important

for their amenity and recreation values. A notable feature of mountain areas, and one which was used to stress their importance in Agenda 21, is the steep climatic, environmental and ecological gradient, and hence diversity of habitats. A range of weather and climate stations are needed in order to understand these gradients more fully, and to be able to demonstrate just how environment is influenced by position and altitude. Two particular topics form a focus for research across the globe at present:

Global warming has implications for the rare and valuable flora and fauna in the Snowdonian mountains. Recent research has suggested that some of the earliest effects of environmental change may be found in mountain vegetation. Over the next few years, it will be possible to build up a record of the year-round ambient conditions and weather on Snowdon so that changes and trends can be identified. Work by the Countryside Council for Wales on Snowdon forms part of the UK Environmental Change Network (ECN) research programme.

Ultra-violet light can be damaging to people and vegetation. Depletion of the protective ozone layer in the upper atmosphere allows more ultra-violet light through to the earth's surface. Little is known about the levels of UV light reaching our mountain summits. A range of sensors manufactured by Skye Instruments in mid Wales have been measuring total solar energy, photosynthetically active radiation and ultra-violet radiation (UVa and UVb).

The second weather station at Clogwyn on Snowdon was installed in the summer of 1998 through collaboration with the Snowdon Mountain Railway Company. The third weather station at Electric Mountain in Llanberis was installed in 1999 through collaboration with the Countryside Council for Wales. These weather stations form a unique network of multi-site, multi-height observation sites.

In a major development with our industrial partner First Hydro, the Snowdon weather stations are now live on the World Wide Web. Steve Sinfield constructed the site on behalf of First Hydro. He also planned and installed the radio network and the system for displaying the information on the WWW. His work has also included developing the web pages and installing web-cameras to provide live views of Snowdon from Elidir Fach.

Our profile of weather stations providing live weather and images on the WWW is a first in the UK. The archive of climate data is now being used in research with UK and European collaborators.


All the weather elements measured are scanned every 5 seconds and the readings are stored in the memory of a 'DataLogger' at the individual site. The information stored in the datalogger is then be summarised over time.

Air temperature:
This is measured using a Stevenson screen to measure the ambient temperature. Two whip sensors, about a metre long, flex in the wind to stop any ice build up. These figures show the minimum, average and maximum temperatures measured for each period (degrees celsius).

The Snowdon summit weather station

A tipping bucket rain gauge measures the total volume of rain falling during that period (millimetres). A straight-sided bucket would fill up to this level (mm) with that amount of rain.

Relative Humidity:
This is the ratio between the amount of water air holds and the amount it could possibly hold, this is given as a percentage. It is worth bearing in mind that as the Snowdon summit station is often in the clouds, it will show a high relative humidity (RH).

A sensor at each weather station measures the total power of the sunshine in kilo Watts per square metre. Strong summer sunshine reaches about 900 w/m2.

Wind speed is measured using an anemometer in miles per hour (M.P.H.). The anemometer on the summit of Snowdon is 20m below the summit and will not always give a perfect reading. It is quite common to see exceptionally high wind speeds at Clogwyn Station which is on a very exposed ridge on Snowdon. When temperatures fall below zero in winter, rime ice may stop the anemometer from turning. Wind direction is measured in degrees, so 270° would convert to due west and 0° would convert to due north.

Wind direction rose

The weather station dataloggers sample the current weather conditions using over 20 different sensors, every 5 seconds. This data is stored in the datalogger to allow interrogation.

Weather station

Every 15 minutes the radio receiver requests the latest data array from the datalogger which is transmitted over 10 km using radio signals. This is then put into a central database to allow easy archival and interrogation.

When someone looks at a web page, the web server requests the latest data 'array' from the database and puts the information into a web page for the public to read.

More information on how Campbell Scientific weather stations work:


Dr Jeremy Williams University of Wales, Bangor. Project founder, co - ordinator and main driving force.
Dave Thomas Cerrig Commercial, Anglesey Technical consultant.
Steve Sinfield First Hydro Company, Llanberis Communications and Internet development.


Responsible For Link

University of Wales, Bangor
The original driving force behind the project.
First Hydro Company
First Hydro provided the technical assistance and infrastructure necessary to get the weather information live on the Internet.
Campbell Scientific
Datalogger, sensors, programming and advice.
Countryside Council for Wales
Funded the weather station and display panel in Electric Mountain.
Meteorological Office
Original collaborator on summit weather station, advice and specialist sensors.
Radio communications at all weather station locations.
Skye Instruments
Sunshine and solar radiation sensors.
Snowdon Mountain Railway
Provided buildings, transport and part funded Clogwyn Station AWS.
Snowdon National Park Authority
Summit building, public display at Pen-y-Pass.
Vector Instruments
The summit weather station has been a 'trial' site for testing new anemometer designs.