Thursday, February 21, 2008

Into every life a little rain must fall!

The weather is an everyday topic of conversation in Ireland. Whether it has the same topicality in other countries, I don’t know, but here in what the visitors call the Emerald Isle we have a particular fascination with anything climatical. It is not so much a topic of conversation as an integral part of a common place greeting, such as ‘lovely weather today’ or more usually ‘more rain on the way’, which are put to those we meet without any preliminary remarks or greetings.

The fascination with the weather in Ireland must surely be related in some way or other to the country’s long-standing dependence on agriculture. The importance of weather in lives devoted to agriculture can be appreciated when one considers that in the years before industrialisation bad weather meant no work and no work meant no pay, the result being hunger within the average family. No wonder, then, that the man in the street became somewhat fixated in what was happening or was expected to happen weather-wise as the working day dawned.

The gathering of weather-related information goes back a long time. How far back, I don’t know, but here in Athy there is a history of involvement in compiling weather data extending back at least 80 years. From 1929 until 1943, a rainfall station operated at Crom a Boo bridge. That same bridge, the work of James Delahunty, ‘Knight of the Trowel’ and completed just two years before the 1798 Rebellion, has been a silent witness to many events and occurrences over the centuries. Decapitated heads have hung from the bridge as a warning to local United Irishmen of the punishment awaiting those who sought to overturn the government of the day. While still in its infancy, the bridge provided safe passage over the River Barrow for Nicholas Grey of Rockfield House and his companion as they started out on their journey to Dublin to join in Emmet’s uprising.

But in 1929 Crom a Boo bridge provided a base for a more practical purpose, when a rainfall station was located there. The modern device for measuring rainfall is a simple enough one consisting of a copper cylinder with a glass bottle inside. The collected rainfall is decanted into a graduated cylinder, giving readings in millimetres. A daily record is kept of the rainfall measured and the information collected is forwarded each month to Met Eireann. Who looked after the rainfall station at Crom a Boo bridge up to 1943 I have been unable to discover and, indeed, I cannot identify exactly where the station was located vis à vis the bridge itself.

The local rainfall station in Athy was relocated to the Vocational School on the Carlow Road in 1943. St Brigid’s School had been opened in 1930 by the then minister for education Thomas Derrig and the late Tony Byrne of St Joseph’s Terrace was in charge of the station in the latter years of his period as school caretaker. I assume that his predecessors in that position were also involved in operating the rainfall station at the school.

Tony Byrne continued operating the rainfall station when in 1980 it was moved to his house at St Joseph’s Terrace, where it remained until Tony’s death in 2003. At the same time, a second station operated at Minch Nortons from 1981 to 2004. Following Tony Byrne’s death, his widow continued to supply rainfall measurements to the Met Office and a member of the Byrne family, I believe, still operates a rainfall station at nearby Levitstown.

Today at Chanterlands, Seosamh May operates a weather recording station on behalf of the Met Office. In addition to rainfall measurement, Seosamh records on a daily basis air temperature, humidity and soil temperatures. His is one of approximately 70 climate stations in Ireland where comprehensive data is compiled each day and forwarded monthly to Dublin. The climate station was previously located at Kilberry from about 1950 until 1993, when it was relocated to Chanterlands from where it has operated on a daily basis for the last 15 years.

I visited the station recently and courtesy of Seosamh May saw at first hand the compact yet seemingly complicated operation which gives the daily weather readings for Athy. The readings are taken at 9am Greenwich Mean Time every day, which means, of course, that during Irish summertime they are taken an hour later at 10am.

The main components of the weather station are a Stevenson’s Screen, a grass minimum thermometer, a rainfall gauge and three soil thermometers. The Stevenson’s Screen was designed originally by Thomas Stevenson, who was the father of the famous author Robert Louis Stevenson. It is a double-louvered box with four thermometers inside. A dry bulb thermometer gives the current air temperature at the time of reading, while a wet bulb thermometer records the temperature of evaporation. Both readings give the relative humidity at reading time. The air maximum thermometer records the highest temperature in a 24-hour period. The air minimum thermometer gives the lowest temperature for the same period. The first three of these thermometers are mercury instruments and the fourth is an alcohol instrument.

On the ground there is a grass minimum thermometer which is also alcohol based, which rests on two ‘Y’ shaped pegs at a 2º slant, with it’s bulb touching grass blade tips. It records the lowest ground temperature during the previous night. The rainfall gauge is similar to that previously described and the rainfall is recorded every day, as are all the other weather measurements.

About a year ago, three soil thermometers were added to the weather station at Chanterlands. These are right-angled instruments and are inserted into the bare soil to depths of 50mms, 100mms and 200mms to give the soil temperature at these respective levels. The information gathered in relation to soil temperature is of benefit to agriculturalists and horticulturalists, for when the soil temperature at 100mms depth reaches 6º C and upwards the grass starts to grow.

Cloud cover is also measured at the Athy weather station and is measured on a scale of 0 Okta, which indicates no cloud, to 9 Okta, which indicates total cloud cover. Visibility is measured and recorded up to 40 meters, 40 meters beyond and less than 20 meters. The state of the ground is recorded on a scale of 0-9 and any special type of weather in a 24-hour period is recorded using code numbers, for example, 2 indicates slow/sleet, 3 hail, 4 thunder, 6 gale and 7 fog.

Keeping daily weather records requires enormous dedication and Seosamh May has successfully under-taken this onerous task for the last 15 years. As an aside, he told me of the difference between a ‘rain day’ and a ‘wet day’. Rain days have rainfall of 0.2mms or above, while wet days have rainfall of 1.0mm or more. Last January, we had 23 rain days and 21 wet days, while the highest temperature recorded this year was on 23 January with almost 14.5º Celsius. The highest temperature recorded at the Athy weather station since 1993 was 31.3º Celsius on 18 July 2006. The heaviest rainfall in any 36-hour period was slightly above 3.5 inches, commencing on 15 May 2000. On the following day just over three inches of rainfall fell. In case you thought that January of this year was bad in terms of rainfall, the wettest month since 1993 was September 1999 when over eight inches of rain fell. This January we had five inches of rain, at a time when the town water supply was cut off, but unfortunately we were unable to avail of either source of water.

Thanks to Seosamh May for showing me around Athy’s weather station and for explaining the intricacies of the system, and thanks also to Joe Lyons of the Met Office in Dublin who supplied most of the information about climatic recordings in the past.

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