readme.txt - Snowdonia Weather Stations Project ----------------------------------------------- You can download the data files from each of the weather stations. They are in comma separated variable (.csv) format which can be read by most spreadsheets including Microsoft Excel, Lotus 123 or any plain text viewer. Excel has a wizard for opening .csv files which will automatically run when you open a file of .csv format. The files are of delimeted format using only commas and for end of line. The first line of each file contains column headings. Files are available at different resolutions: Folder Description ------ ------------------------------------------------------ /15min - Data not summarised and created every 15 minutes /60min - Data summarised hourly and created every hour /1day - Data summarised daily and created once a day /met - Data not sumamrised and raw out of the database Each file is named after the station it is generated from. Click the filename to download, then follow the prompts. Depending on your system software, you may need to right hand click on the icon and choose 'save target/link as'. All the weather elements measured are scanned every 5 seconds and the readings are then stored in the memory of a 'DataLogger' at the individual site. The information stored in the datalogger has then be summarised over time. Air temperature: ---------------- This is measured using a Stevenson screen to measure the ambient temperature, also there are two whip sensors which are about a metre long and 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) Rain: ----- 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). Sunshine: --------- 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 Airflow: -------- Wind speed is measured using an anemometer in miles per hour (M.P.H.) It is worth bearing in mind that 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 temperaturs fall below zero in winter, rime ice may stop the anemometer from turning, and give a reading of 0 (this can be checked by looking at the corresponding temperature for that period). Wind direction is measured in degrees, so 270° would convert to due west and 0° would convert to due north. Technical Overview ------------------ At each weather station site there is a datalogger which samples the current weather conditions using over 20 different sensors, every 5 seconds. This data is stored in the datalogger to allow interrogation. Every 15 minutes the radio receiver requests the latest data array from the datalogger it is transmitted using 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: http://www.campbellsci.co.uk/products/weather/weather.htm -------------------------- Steve Sinfield 22-Jul-1999 --------------------------