Report on
rainfall extreme in Ireland
and US
Introduction
There are several main rainfall
statistics terms, including return period, duration, rainfall intensity,
frequency and rainfall amount, etc. Usually, the rainfall data could be
collected by EPA and OPW in Ireland. The accumulated data can be used to draw a Intensity-Duration-Frequency graph. The IDF relationship,
which shows in the graph, is the main processed data in studying
rainfall and flood issues.
Relationship of
return period, duration and rainfall amounts
Normally, the rainfall
amount is equal to the product of average rainfall intensity multiples rainfall
duration. Return period could be seen the frequencies of different level floods.
Hence, the
relationship of these three terms is just the Intensity-Duration-Frequency
relationship.
Return period
could be observed in the Intensity-Duration-Frequency relationship graph, as
below.
Chris, 2010 Intensity Duration Frequency for London
The equation of return period, duration and
rainfall intensity is often hard to get. But it is sure that the equation shows
a logarithmic relationship of IDF.
Irish extremes
and US extremes
By visiting the website of Irish
Meteorological Service Online, it is possible to receive the
Irish weather extremes. After summarizing the records, the rainfall data could
be sum-upped as two tables below.
Table
1 Ireland Rainfall Records for Highest Rainfall
|
Highest Rainfall
|
|||
|
|
Time
|
Location
|
Amount (mm)
|
|
Hourly
|
27th, Jun.
1986
|
Clonroche, Co. Wexford
|
52.2
|
|
Daily
|
18th, Sep.1993
|
Cloone Lake, Co. Kerry
|
243.5
|
|
Monthly
|
Oct. 1996
|
Cummeragh Mtns
|
790.0
|
|
Annually
|
1960
|
Ballaghbeama
|
3964.9
|
Table
2 Ireland Rainfall Records for Lowest Rainfall and Absolute Draught
|
Lowest
|
Absolute draught
|
|||
|
Time
|
Location
|
Amount (mm)
|
Period
|
Location
|
|
1887
|
Glasnevin, Dublin
|
356.6
|
3rd April to 10th May
1938
|
Limerick
|
The UK rainfall extremes could be
obtained from the website of Met office, as below.
Table 3 Highest 24-hour rainfall totals for a rainfall
day (0900-0900 GMT)
|
Country
|
Rainfall (mm)
|
Date
|
Location
|
|
England
|
279
|
18 July 1955
|
Martinstown (Dorset)
|
|
Scotland
|
238
|
17 January 1974
|
Sloy Main Adit (Argyll
& Bute)
|
|
Wales
|
211
|
11 November 1929
|
Lluest Wen Reservoir
(Mid Glamorgan)
|
|
Northern Ireland
|
159
|
31 October 1968
|
Tollymore Forest
(County Down)
|
Table
4 UK rainfall records for consecutive rainfall days (0900-0900 GMT)
|
Days
|
Rainfall (mm)
|
Date
|
Location
|
|
Highest 2-day total
|
405.0
|
4 to 5 December 2015
|
Thirlmere (Cumbria)
|
|
Highest 3-day total
|
456.4
|
17 to 19 November 2009
|
Seathwaite (Cumbria)
|
|
Highest 4-day total
|
495.0
|
16 to 19 November 2009
|
Seathwaite (Cumbria)
|
The UK government also took very short
duration rainfall records as highest 5-miniute total, highest 30-minute
rainfall, etc. It is quite the same as Irish statistics format. Irish
statistics period of a day also starts from 9:00am to the next 9:00am. There
are 9 durations between 15 minutes to 24 hours.
Conclusion
The highest
daily score of Ireland is quite close to the highest score in UK but not the
same year.
Reference
Chris.
(2010). Intensity Duration Frequency for London. WordPress. Available at: https://thecriticalflow.wordpress.com/2010/09/06/intensity-duration-frequency-for-london/ [Accessed date: April 18th,
2016]
Irish Meteorological Service. (2013). Irish
Weather Extremes. Irish Meteorological Service Online. Available at : http://www.met.ie/climate-ireland/weather-extremes.asp [Accessed date: April 18th,
2016]
Met Office. (2016). UK climate – Extremes.
Met Office online.
Available at : http://www.metoffice.gov.uk/public/weather/climate-extremes/#?tab=climateExtremes [Accessed date: April 18th,
2016]
