Fundamental sensor response time limitations of practical air temperature measurement

Harrison, R. G. ORCID: https://orcid.org/0000-0003-0693-347X and Burt, S. D. (2025) Fundamental sensor response time limitations of practical air temperature measurement. Geophysical Research Letters, 52 (20). e2025GL118464. ISSN 1944-8007 doi: 10.1029/2025GL118464

Abstract/Summary

Air temperature measurements in naturally ventilated thermometer screens underpin the instrumental climate record. Increasing automation is, however, revealing limitations. One is through thermometer time response, especially in light winds or calm conditions, often at the daily temperature minimum. The exponential time response τ_63 for thermometers enclosed within a Stevenson screen is a key parameter, but poorly known. Here, τ_63 is evaluated in a practical experimental situation against the World Meteorological Organization (WMO)’s recommended sensor τ_63≤20 s. We find τ_63 increases with sensor diameter d, with only a d=2 mm sensor meeting WMO expectations, even then requiring ambient wind speeds ≥3 ms^(-1). Typical d=4 mm sensors never meet the criterion when either force- or naturally ventilated, with τ_63≥20 mins in a naturally ventilated arrangement under calm conditions. Inadequate τ_63 will lead to underestimation of the diurnal temperature range or other local changes derived from daily temperature maxima and minima.

Item Type	Article
URI	https://centaur.reading.ac.uk/id/eprint/125191
Identification Number/DOI	10.1029/2025GL118464
Refereed	Yes
Divisions	Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
Publisher	American Geophysical Union
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