Daily, validated and automated in-situ ground-based meteorological observations in the Netherlands

KNMI collects in-situ meteorological observations in the Netherlands aggregated into hourly, daily, monthly, and annual datasets. These data are derived from the 10-minute automatic measurements since the early 1990s, hourly observations from 1951 and daily observations from 1901. The earliest data starts in 1901 with one station and gradually increases to the current measurement network of more than 50 automatic weather stations.

The weather stations measure essential climate variables (ECVs), surface precipitation, pressure, global radiation, temperature, water vapor, wind speed and direction, clouds, and visibility. Sunshine duration and potential evapotranspiration are calculated from the ECVs. When applicable, minima, maxima, means, and sums are defined or calculated.

This dataset contains meteorological observations since 1901-01-01 at a daily interval. To form this dataset, hourly observations have been aggregated to daily intervals. When applicable, hourly intervals are calculated in which the minimum or maximum occurred during the day. Before aggregation to daily intervals, the hourly data has undergone manual validation by KNMI experts, filling gaps and correcting measurement errors, after which it becomes available. The expert validation can take 1-10 working days to complete. Validated data can be modified at any moment in the future if further issues are found with the data.