An Intercomparison of Precipitation Gauges at KNMI in De Bilt, Netherlands

The Royal Netherlands Meteorological Institute (KNMI) conducted an intercomparison of precipitation gauges to identify a suitable replacement for the floating-type gauge (FG) currently operational in its automated network. Replacement, by a commercial off-the-shelf instrument, is needed as KNMI designed gauges have been operational for 30 years, thus purchasing replacement parts and making repairs is becoming increasingly unsustainable.

The following two precipitation gauges, each with different collection methodologies, were installed in September 20201 on the test field at KNMI’s headquarters in De Bilt, NL after successful lab tests were performed during the summer leading up to installation.

1. Lambrecht-Meteo’s rain[e] H3 hybrid gauge (HG), combination of tipping bucket and weighing gauge

2. OTT HydroMet’s Pluvio2 L Weighing Gauge (WG)

These gauges under test were collocated with three of KNMI’s current gauges and concurrently collected data at a 1-min resolution during a field trial of one year, covering a wide variety of meteorological conditions. One of these three was in a pit at ground level following the WMO recommended gauge configuration and is referred to as ‘WMO’. This gauge was used as the reference gauge for the intercomparison. The other two (control gauges) were used to measure the quality of data and to confirm expected differences, for example differences due to exposure (i.e., wind.) One of these sensors, with its orifice 1-meter above ground, was like the gauges under test (hereafter, ‘VONS’), and the other was in a so-called ‘English pit’ (hereafter, ‘AWS’.) Ancillary measurements in the setup consisted of a (default) automatic weather station and surface wind and precipitation detection at orifice height.

In this paper, the analysis methodology will be outlined, challenges will be discussed, and results will be presented. Included in the analysis will be comparisons of precipitation amounts and intensities and their differences, as well as the duration of precipitation events. The results will assist KNMI in developing specifications for a European tender for the acquisition of a suitable replacement precipitation gauge for its automated network.