The De-Icing Comparison Experiment (D-ICE): a study of broadband radiometric measurements under icing conditions in the Arctic
Surface-based measurements of broadband shortwave (solar) and longwave (infrared) radiative fluxes using thermopile radiometers are made regularly around the globe for scientific and operational environmental monitoring. The occurrence of ice on sensor windows in cold environments – whether snow, ri...
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| Published in: | Atmospheric measurement techniques Vol. 14; no. 2; pp. 1205 - 1224 |
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| Main Authors: | , , , , , , , , , |
| Format: | Journal Article |
| Language: | English |
| Published: |
Katlenburg-Lindau
Copernicus GmbH
16-02-2021
Copernicus Publications |
| Subjects: | |
| Online Access: | Get full text |
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| Summary: | Surface-based measurements of broadband shortwave (solar)
and longwave (infrared) radiative fluxes using thermopile radiometers are
made regularly around the globe for scientific and operational environmental
monitoring. The occurrence of ice on sensor windows in cold environments –
whether snow, rime, or frost – is a common problem that is difficult to
prevent as well as difficult to correct in post-processing. The Baseline
Surface Radiation Network (BSRN) community recognizes radiometer icing as a
major outstanding measurement uncertainty. Towards constraining this
uncertainty, the De-Icing Comparison Experiment (D-ICE) was carried out at
the NOAA Atmospheric Baseline Observatory in Utqiaġvik (formerly
Barrow), Alaska, from August 2017 to July 2018. The purpose of D-ICE was to
evaluate existing ventilation and heating technologies developed to mitigate
radiometer icing. D-ICE consisted of 20 pyranometers and 5 pyrgeometers
operating in various ventilator housings alongside operational systems that
are part of NOAA's Barrow BSRN station and the US Department of Energy
Atmospheric Radiation Measurement (ARM) program North Slope of Alaska and
Oliktok Point observatories. To detect icing, radiometers were monitored
continuously using cameras, with a total of more than 1 million images of
radiometer domes archived. Ventilator and ventilator–heater performance
overall was skillful with the average of the systems mitigating ice formation
77 % (many >90 %) of the time during which icing conditions
were present. Ventilators without heating elements were also effective and
capable of providing heat through roughly equal contributions of waste
energy from the ventilator fan and adiabatic heating downstream of the fan.
This provided ∼0.6 ∘C of warming, enough to subsaturate the
air up to a relative humidity (with respect to ice) of ∼105 %.
Because the mitigation technologies performed well, a near complete record
of verified ice-free radiometric fluxes was assembled for the duration of
the campaign. This well-characterized data set is suitable for model
evaluation, in particular for the Year of Polar Prediction (YOPP) first
Special Observing Period (SOP1). We used the data set to calculate short-
and long-term biases in iced sensors, finding that biases can be up to +60 W m−2 (longwave) and −211 to +188 W m−2 (shortwave). However,
because of the frequency of icing, mitigation of ice by ventilators, cloud
conditions, and the timing of icing relative to available sunlight, the
biases in the monthly means were generally less than the aggregate
uncertainty attributed to other conventional sources in both the shortwave
and longwave. |
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| Bibliography: | USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Solar Energy Technologies Office NREL/JA-5D00-77633 AC36-08GO283; SC0013306; AC36-08GO28308 |
| ISSN: | 1867-8548 1867-1381 1867-8548 |
| DOI: | 10.5194/amt-14-1205-2021 |