The Construction of a Central Netherlands Temperature

The Central Netherlands Temperature record (CNT) is a monthly daily mean temperature time series that is representative for a region in the centre of the country, i.e., excluding the coast, north and south. It has been constructed to study large-scale temperature changes and facilitate comparisons with climate models, which resolve similar scales.

From 1906 onwards temperature observations in the Netherlands have been sufficiently standardised to construct a high-quality series. Long time series have been constructed by merging nearby stations, using the overlap periods to calibrate the differences. These long time series have been subjected to a homogeneity analysis. Significant breaks and trends have been corrected. Many, but not all, breaks correspond to changes in the observations that are documented in the station metadata.

The current version of the Central Netherlands Temperature (CNT4,6) is constructed as the unweighted average of four stations until 1950 (De Bilt, Winterswijk/Hupsel, Oudenbosch/Gilze-Rijen and Gemert/Volkel), and six stations afterwards (Deelen and Eindhoven added to the previous stations). The RMS difference with the observed temperature at De Bilt is 0.11ºC for annual means, and 0.07ºC with the De Bilt series that has been homogenised using physical methods. The trend is slightly lower than the trend in the De Bilt series over the last 60 years.

The CNT data are available at www.knmi.nl and are updated monthly.