Toward autonomous surface-based infrared remote sensing of polar clouds: retrievals of cloud optical and microphysical properties
Improvements to climate model results in polar regions require improved knowledge of cloud properties. Surface-based infrared (IR) radiance spectrometers have been used to retrieve cloud properties in polar regions, but measurements are sparse. Reductions in cost and power requirements to allow more...
Published in: | Atmospheric Measurement Techniques |
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Online Access: | https://doi.org/10.5194/amt-12-5071-2019 https://amt.copernicus.org/articles/12/5071/2019/ |
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ftcopernicus:oai:publications.copernicus.org:amt76776 2023-05-15T15:13:11+02:00 Toward autonomous surface-based infrared remote sensing of polar clouds: retrievals of cloud optical and microphysical properties Rowe, Penny M. Cox, Christopher J. Neshyba, Steven Walden, Von P. 2019-09-23 application/pdf https://doi.org/10.5194/amt-12-5071-2019 https://amt.copernicus.org/articles/12/5071/2019/ eng eng doi:10.5194/amt-12-5071-2019 https://amt.copernicus.org/articles/12/5071/2019/ eISSN: 1867-8548 Text 2019 ftcopernicus https://doi.org/10.5194/amt-12-5071-2019 2020-07-20T16:22:39Z Improvements to climate model results in polar regions require improved knowledge of cloud properties. Surface-based infrared (IR) radiance spectrometers have been used to retrieve cloud properties in polar regions, but measurements are sparse. Reductions in cost and power requirements to allow more widespread measurements could be aided by reducing instrument resolution. Here we explore the effects of errors and instrument resolution on cloud property retrievals from downwelling IR radiances for resolutions of 0.1 to 20 cm −1 . Retrievals are tested on 336 radiance simulations characteristic of the Arctic, including mixed-phase, vertically inhomogeneous, and liquid-topped clouds and a variety of ice habits. Retrieval accuracy is found to be unaffected by resolution from 0.1 to 4 cm −1 , after which it decreases slightly. When cloud heights are retrieved, errors in retrieved cloud optical depth (COD) and ice fraction are considerably smaller for clouds with bases below 2 km than for higher clouds. For example, at a resolution of 4 cm −1 , with errors imposed (noise and radiation bias of 0.2 mW/(m 2 sr cm −1 ) and biases in temperature of 0.2 K and in water vapor of −3 %), using retrieved cloud heights, root-mean-square errors decrease from 1.1 to 0.15 for COD, 0.3 to 0.18 for ice fraction ( f ice ), and 10 to 7 µ m for ice effective radius (errors remain at 2 µ m for liquid effective radius). These results indicate that a moderately low-resolution, surface-based IR spectrometer could provide cloud property retrievals with accuracy comparable to existing higher-resolution instruments and that such an instrument would be particularly useful for low-level clouds. Text Arctic Copernicus Publications: E-Journals Arctic Atmospheric Measurement Techniques 12 9 5071 5086 |
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Open Polar |
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Copernicus Publications: E-Journals |
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ftcopernicus |
language |
English |
description |
Improvements to climate model results in polar regions require improved knowledge of cloud properties. Surface-based infrared (IR) radiance spectrometers have been used to retrieve cloud properties in polar regions, but measurements are sparse. Reductions in cost and power requirements to allow more widespread measurements could be aided by reducing instrument resolution. Here we explore the effects of errors and instrument resolution on cloud property retrievals from downwelling IR radiances for resolutions of 0.1 to 20 cm −1 . Retrievals are tested on 336 radiance simulations characteristic of the Arctic, including mixed-phase, vertically inhomogeneous, and liquid-topped clouds and a variety of ice habits. Retrieval accuracy is found to be unaffected by resolution from 0.1 to 4 cm −1 , after which it decreases slightly. When cloud heights are retrieved, errors in retrieved cloud optical depth (COD) and ice fraction are considerably smaller for clouds with bases below 2 km than for higher clouds. For example, at a resolution of 4 cm −1 , with errors imposed (noise and radiation bias of 0.2 mW/(m 2 sr cm −1 ) and biases in temperature of 0.2 K and in water vapor of −3 %), using retrieved cloud heights, root-mean-square errors decrease from 1.1 to 0.15 for COD, 0.3 to 0.18 for ice fraction ( f ice ), and 10 to 7 µ m for ice effective radius (errors remain at 2 µ m for liquid effective radius). These results indicate that a moderately low-resolution, surface-based IR spectrometer could provide cloud property retrievals with accuracy comparable to existing higher-resolution instruments and that such an instrument would be particularly useful for low-level clouds. |
format |
Text |
author |
Rowe, Penny M. Cox, Christopher J. Neshyba, Steven Walden, Von P. |
spellingShingle |
Rowe, Penny M. Cox, Christopher J. Neshyba, Steven Walden, Von P. Toward autonomous surface-based infrared remote sensing of polar clouds: retrievals of cloud optical and microphysical properties |
author_facet |
Rowe, Penny M. Cox, Christopher J. Neshyba, Steven Walden, Von P. |
author_sort |
Rowe, Penny M. |
title |
Toward autonomous surface-based infrared remote sensing of polar clouds: retrievals of cloud optical and microphysical properties |
title_short |
Toward autonomous surface-based infrared remote sensing of polar clouds: retrievals of cloud optical and microphysical properties |
title_full |
Toward autonomous surface-based infrared remote sensing of polar clouds: retrievals of cloud optical and microphysical properties |
title_fullStr |
Toward autonomous surface-based infrared remote sensing of polar clouds: retrievals of cloud optical and microphysical properties |
title_full_unstemmed |
Toward autonomous surface-based infrared remote sensing of polar clouds: retrievals of cloud optical and microphysical properties |
title_sort |
toward autonomous surface-based infrared remote sensing of polar clouds: retrievals of cloud optical and microphysical properties |
publishDate |
2019 |
url |
https://doi.org/10.5194/amt-12-5071-2019 https://amt.copernicus.org/articles/12/5071/2019/ |
geographic |
Arctic |
geographic_facet |
Arctic |
genre |
Arctic |
genre_facet |
Arctic |
op_source |
eISSN: 1867-8548 |
op_relation |
doi:10.5194/amt-12-5071-2019 https://amt.copernicus.org/articles/12/5071/2019/ |
op_doi |
https://doi.org/10.5194/amt-12-5071-2019 |
container_title |
Atmospheric Measurement Techniques |
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12 |
container_issue |
9 |
container_start_page |
5071 |
op_container_end_page |
5086 |
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1766343777388068864 |