102 homogenised stations 1910-now
),240 homogenised stations 1951-now
The raw data are from the 8-8 observational network, the day is the day of the observation, most rain fell on the previous day. The homogenised set has been corrected statistically for breaks in the monthly sum in comparisons with neighbouring stations. The lowering of the observation height from 1.5m to 0.4m around 1950 has not been corrected for. This reduced the undercatch by about 3% but the correction depends strongly on the location and weather. A first order correction for measurement problems 2012-2017 has been added.
These observations are from automatic rain gauges, which on average record about 5% less rain than the manual rain gauges of the 8-8 network.
The daily precipitation deficit, cumulative Makkink evaporation minus precipitation (set to zero when negative):
In the Netherlands, the precipitation deficit is defined as the cumulative potential evaporation (according to Makkink) minus precipitation starting from 1 April and set to zero when it would become negative.
The official series is based on thirteen 8-8 rain gauge series and potential evaopartion derived from De Bilt temperature and sunshine 1906-2000. From 2001 onward it is computed from the same 13 manual rain gauge stations and temperature and sunshine at automatic stations closest to these precipitation stations. This series is plotted here
. The unofficial series use all automatic stations for precipitation, temperature and sunshine (so a varying number of stations
). The automatic rain gauges record on average about 5% less rain than the manual rain gauges.