Preprints
https://doi.org/10.5194/amt-2021-63
https://doi.org/10.5194/amt-2021-63

  15 Apr 2021

15 Apr 2021

Review status: a revised version of this preprint is currently under review for the journal AMT.

Effect of snow-covered ground albedo on the accuracy of air temperature measurements

Chiara Musacchio1, Graziano Coppa1, Gaber Begeš2, Christina Hofstätter-Mohler3, Laura Massano4, Guido Nigrelli5, Francesca Sanna6, and Andrea Merlone1 Chiara Musacchio et al.
  • 1Istituto Nazionale di Ricerca Metrologica, Strada delle Cacce 91, 10135 Torino, Italy
  • 2Univerza v Ljubljani – Laboratorij za Metrologijo in Kakovost, Ljubljana, Slovenia
  • 3Bundesamt für Eich- und Vermessungswesen, Wien, Austria
  • 4Università degli Studi di Torino, Italy
  • 5Istituto di Ricerca per la Protezione Idrogeologica - Consiglio Nazionale delle Ricerche, Strada delle Cacce 73, 10135 Torino, Italy
  • 6Istituto per le Macchine Agricole e Movimento Terra - Consiglio Nazionale delle Ricerche, Strada delle Cacce 73, 10135 Torino, Italy

Abstract. Solar radiation is one of the main factors introducing significant deviations between thermometers reading and true air temperature value. Techniques to protect the sensors from direct radiative influence have been adopted almost since the beginning of meteorological observations. Reflected radiation from snow-covered surface can also cause extra warming to thermometers hosted in solar shields, not always optimized to protect the sensors from this further backward radiative heat transfer. This phenomenon can cause errors in near-surface temperature data series, with relevant impact on the quality of data records. The study here presented experimentally evaluates the effect of albedo radiation from snow-covered surface, on the accuracy of air temperature measurements. The investigation is based on evaluating temperature differences between couples of identical instruments positioned above ground covered by natural vegetation, being one in snow-free conditions and the other above snow-covered surface, at the same time in the same site in close vicinity. The work involved a representative number of different typologies of sensors and shields from different manufactures. A mountain site with appropriate field conditions, offering long-lasting snow presence to maximize data availability, was selected to host the experiment. Quantities of influence such as relative humidity, wind speed and direction, solar radiation (direct and reflected) were constantly measured. The effect was evaluated to range up to more than 3 °C for some typologies of sensors. Full data analysis is here reported, together with complete results. This main scope of this work is to report on an experimental estimation and method to evaluate and include this effect as a component of uncertainty in temperature data series for near-surface stations above snowy areas.

Chiara Musacchio et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Review of “Effect of snow-covered ground albedo on the accuracy of air temperature measurements” by Musacchio et al.', Craig Smith, 07 May 2021
    • AC1: 'Reply on RC1', Graziano Coppa, 18 May 2021
      • RC2: 'Reply on AC1', Craig Smith, 20 May 2021
        • AC2: 'Reply on RC2', Graziano Coppa, 21 May 2021
    • AC4: 'Reply on RC1', Graziano Coppa, 14 Jul 2021
  • RC3: 'Comment on amt-2021-63', Hendrik Huwald, 22 Jun 2021
    • AC3: 'Reply on RC3', Graziano Coppa, 14 Jul 2021

Chiara Musacchio et al.

Chiara Musacchio et al.

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Short summary
In the context of the overhaul of WMO/CIMO guide #8 on instruments and methods of observation, we performed an experiment to quantify uncertainties in air temperature measurements due to reflected solar radiation from a snow-covered surface. Couples of sensors with different radiation shields were put under different ground conditions (grass vs snow) for a whole winter. Results show that different shields may reduce the influence of backward radiation, which can produce errors up to 3 °C.