We have meteorological records stretching back to December 1794, with continuous records starting in July 1975. There is a lack of data between June 1825 to December 1832, known as ‘the Armagh gap’: a record book appears to be missing, and several generations of Directors, Librarians, and Weather Observers have so far failed to find it.
While unlikely, it is possible the gap in the records is real (i.e., that no one actually took the readings in that time). This uncertainty is the reason the title of ‘the longest continuous meteorological record in the British Isles’ is sometimes attributed to the Radcliffe Observatory in Oxford: their continuous records start in 1815 (with intermittent observations since 1772).
The figure below illustrates the length of the Armagh climate series for various meteorological parameters. The following sections discuss the data which has been digitised, the scans of record books, and the abbreviations and codes used.
-
About the Digitised Data
The digitised database includes calibrated data from 1838-1904 to 2001-2004 (depending on the parameter; see below). The data after that cut-off has not yet been corrected for instrumental sensitivity, exposure of the instruments or the time of observation; it is copied directly from our record books.
Data from 1853 onwards is also held in the Met Office database along with other historic stations (Armagh data is here). Much of the historic data for Armagh is held at the Public Record Office Northern Ireland (PRONI) as well, with start dates in the 1860s and 1870s for most types of data.
Unless otherwise specified (e.g. ‘evening wet bulb’), all readings were taken in the morning on any given day. Since 1938, the standard has been 09:00 GMT, but this has varied between 08:27 and 10:27 GMT over the earlier years. Rainfall is measured between two consecutive morning readings, whereas sunshine is measured midnight to midnight. Evening readings were taken around 21:00 GMT, but the standard changed, like the morning one, so the reading time varied from 20:27 to 22:27 GMT. Such matters are discussed in more detail in the relevant Publications.
Calibrated data
Rainfall:
01/01/1838 to 31/12/2001
Temperature:
Morning present/dry bulb: 02/01/1838 to 31/12/2004
Morning wet bulb: 02/01/1838 to 31/12/2004
Evening present/dry bulb: 01/01/1844 to 08/03/1965
Evening wet bulb: 01/01/1844 to 08/03/1965
Daily minimum: 01/01/1844 to 31/12/2004
Daily maximum: 01/01/1844 to 31/12/2004Soil temperature:
30 cm depth: 21/04/1904 to 31/12/2002
100 cm depth: 21/04/1904 to 31/12/2002Sunshine:
21/04/1880 to 31/12/2004
Uncalibrated data
This includes measurements of the same parameters as above from the stated end date until the present day, with the exception of evening measurements, which were discontinued in 1965. Additionally, the following parameters are shown (either as part of the daily summary or as a graph):
Grass minimum temperature:
01/07/2000 to present
Pressure at 9am GMT:
01/01/1850 to present
Humidity (calculated from dry and wet bulb)
Morning humidity: 02/01/1838 to 31/12/2004
Evening humidity: 03/01/1844 to 31/12/1965Wind
Wind speed: 01/07/2000 to present
Wind direction: 01/07/2000 to presentConditions
Total cloud: 01/07/2000 to present
Visibility: 01/07/2000 to present
Present weather/weather at observation: 01/07/2000 to present
State of ground: 01/07/2000 to presentAttached Scans
If you chose to explore data for a single day, ‘Show scans’ option will appear if available. If a single date is chosen under the advanced option, the relevant scans from the corresponding month will be displayed under ‘More data’, if available. This only stretches as far back as the digitised data (i.e. January 1838); for a more comprehensive view of the scanned record books, see Scans of Record Books below.
-
Scans of Record Books
The scans from the original record books contain the raw meteorological data between December 1794 and June 2000, but excluding April 1795 to June 1795 and June 1825 to December 1832 (‘the Armagh gap’). Data from July 2000 onwards is available in a digital format rather than as a scanned image.
This data has not been calibrated and is presented as-is for your perusal. It has not been corrected for instrumental sensitivity, exposure of the instruments or the time of observation. It is contained in tables of observed variables with some general comments on the weather by the observer. The button below will direct you to a folder where the records for every year have been collated into a single PDF document. This means you will sometimes find information from several different books collated together. The scans are currently available internally only – please contact us if you wish to peruse them.
The measurements and their presentation have changed significantly over the centuries, so a single guide to reading these pages cannot be provided. Each distinct set of measurements therefore comes with its own description of formatting. You can also learn more about abbreviations and codes used in the observer’s diary further down this section.
The below figure is a scan of the first weather readings – temperature and pressure – taken at Armagh Observatory from December 1794 onwards. An unbroken record began in July 1795.
-
Abbreviations and Codes Used in the Observer's Diary
While the notation has varied over the centuries, a standard for meteorological abbreviations and codes used in the observer’s diary has been slowly established. The following link contains tables with modern versions of such codes, which can help you better understand the comments accompanying the daily measurements.
-
Beaufort's Weather Codes
Sir Francis Beaufort (1774 – 1857) was an Irish hydrographer and later rear admiral of the Royal Navy. He is most famous for the invention of an empirical measure relating observable conditions on land or at sea to wind speed which bears his name: Beaufort scale. He conducted other meteorological observations as well, and had his personal notation (weather codes) which changed slowly with time.
-
Disclaimer
The information contained in this data archive is owned by the Armagh Observatory and Planetarium (AOP) which retains copyright. Whilst AOP has made every effort to ensure accuracy, we cannot be held responsible for errors or omissions. Some data is uncalibrated and should be used with caution; other data has been calibrated to the best of our ability but may still contain systematic and sporadic errors. If errors are spotted in the data please contact us.
