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A methodology for study of in-service drift of meteorological humidity sensors.

Bell, S A; Carroll, P A; Beardmore, S L; England, C*; Mander, N* (2017) A methodology for study of in-service drift of meteorological humidity sensors. Metrologia, 54 (3). S63-S73

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Meteorological measurements of air humidity in ground-based weather stations worldwide are increasingly being used in studies of climate change. However, electronic humidity sensors often suffer gradual drift in sensor readings, particularly at the high end of the relative humidity range. This phenomenon is well known, but there is currently limited quantitative information available about the drift characteristics, and hence about the consequent measurement bias or uncertainty that should be attributed to historical humidity data sets.

In order to quantify weather-station hygrometer drift, a dataset has been studied from UK weather-station hygrometer records supplied by the UK Met Office calibration laboratory. As well as documenting the calibrations and adjustments, the records include 'as-found' checks of the hygrometers on return from field use. This allows average in-service error and drift to be evaluated for the population of instruments.

The approach of the study is presented, together with illustrative initial results quantifying mean sensor drift of up to 5%rh. The implications of this for estimating bias in observations are discussed, along with discussion of associated uncertainty. This includes consideration of the distribution of the data, including the end-limited range where readings are capped at 100%rh. The study results justify the Met Office practice of adjusting hygrometers to minimise the errors in use. Preliminary conclusions and recommendations are made, and further steps are identified for developing the methodology.

Item Type: Article
Keywords: hygrometer, drift, weather station, climate, humidity, metrology for meteorology
Subjects: Engineering Measurements
Engineering Measurements > Thermal
Divisions: Engineering, Materials & Electrical Science
Identification number/DOI: 10.1088/1681-7575/aa6dd0
Last Modified: 02 Feb 2018 13:12
URI: http://eprintspublications.npl.co.uk/id/eprint/7570

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