A quick overview from Met Éireann's rainfall climate page:
Most of the eastern half of the country gets between 750 and 1000 (mm) of rainfall in the year. Rainfall in the west generally averages between 1000 and 1400 mm. In many mountainous districts rainfall exceeds 2000mm per year.Rainfall shows great year to year variability. A 30 year running mean of the national annual rainfall indicated an increase in average national rainfall of approximately 70mm over the last two decades.
The average number of wet days (days 1mm or more of rain) ranges from about 150 days a year along the east and south east coasts, to about 225 days a year in parts of the west.
Annual rainfall map:
What do I need to look at to define a precipitation climate?
Precipitation is quite a noisy variable to deal with, and there are lots of ways to look at it. Climate Change Indices have been defined by the Expert Team on Climate Change Detection, Monitoring and Indices (ETCCDMI):http://etccdi.pacificclimate.org/list_27_indices.shtml
Ones that I've used here are:
- PRCPTOT: Total precipitation in wet (>1mm) days.
- SDII: Simple Daily Intensity Index. Mean precipitation amount for wet days (mm/wet day)
- R10mm: Heavy Precipitation Days. No. days >10mm
- CDD: Max no. Consecutive Dry (<1mm) Days
- CWD: Max no. Consecutive Wet (>=1mm) Days
