When the weather readings began at Armagh Observatory over 200 years ago, only present temperature and pressure were recorded. Today, the weather observations continue to be made every day in Armagh at 9am GMT. The climate record is now the longest in the UK and Ireland.
Shane Kelly is the principal meteorological observer. He has been so for over 20 years now, the longest period any one person has held this responsibility since the Observatory was built. When Shane is not available, Armagh PhD students step in to make the observations. This now forms a part of the training they receive in the skills of scientific measurement.
The full suite of data collected has grown over the years. It includes recording the present temperature and pressure, the daily maximum and minimum temperatures, and the grass surface and soil temperatures. This has application, for instance, to agriculture, guiding when to plant crops. Most instruments are enclosed inside the Stevenson Screen, with others located around the Met Enclosure.
The amount of sunshine each day is measured using a Campbell-Stokes sunshine recorder; a glass ball which concentrates the sunlight to burn a strip along a special card. Present cloud cover, wind speed and direction, general weather, and the state of ground are also recorded.
A new Automatic Weather Station has been added recently, able to sample conditions minute-by-minute and so increase the richness of the dataset.
The Armagh dataset contributes to quantifying our understanding of how the climate has changed over the past. It shows a clear warming trend over the past three decades. As the oldest Centennial station in the UK and Ireland, maintaining and continuing this record of daily weather measurements in Armagh is particularly important.
The Armagh Observatory meteorological enclosure, or ‘Met Enclosure’ for short, contains the majority of our meteorological instruments; only the barometers are situated indoors, in the Library building. The elements of the enclosure are labelled in the above photograph as follows (blue numbers denote parts belonging to the current AWS, grey are old rain gauges):
- Stevenson Screen (see below for contents)
- 30 cm soil thermometer
- Grass minimum thermometer
- 100 cm soil thermometer
- Standard 5-inch brass rain gauge
- Old automatic rain gauge (see e.g. old videos)
- Old automatic rain gauge (from AWS 2001-2006)
- New automatic rain gauge (for current AWS)
- Concrete minimum thermometer (for current AWS)
- Sunshine tower with Campbell-Stokes sunshine recorder and old AWS equipment
- Representative patch of ground
- Current AWS main tower
- Soil minimum thermometers (for current AWS)
The Stevenson screen is the heart of meteorological readings. It primarily contains a number of thermometers there to maintain a reliable record of readings. Its elements are labelled in the above photograph as follows (red numbers denote parts that don’t need attention on a daily basis):
- Precision thermometer
- Vaisala graphing temperature sensor
- Main alcohol minimum thermometer
- Backup alcohol minimum thermometer
- Wet bulb thermometer (with wick)
- Wet bulb thermometer water vessel
- Graduated measuring cylinder (hidden from sight here)
- Rainwater collection bottle
- Spool of string for wind direction determination (hidden from sight here)
Campbell-Stokes Sunshine Recorder
A top the sunshine tower sits perhaps the most striking instrument in our collection: the Campbell-Stokes sunshine recorder. It has changed very little since its first full design in 1880: a large glass ball concentrates sunlight to burn a strip along a special card. From the burnt line, the amount of sunshine can be determined.
It is positioned atop the tower to improve the Sun’s reach in the mornings and evenings, when trees might otherwise obscure it. A lower tower used to be used (positioned in place of the current AWS), but the trees keep growing!