Thin ice clouds in the Arctic: cloud optical depth and particle size retrieved from ground-based thermal infrared radiometry
Multiband downwelling thermal measurements of zenith sky radiance, along with cloud boundary heights, were used in a retrieval algorithm to estimate cloud optical depth and effective particle diameter of thin ice clouds in the Canadian High Arctic. Ground-based thermal infrared (IR) radiances fo...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2017-06-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | http://www.atmos-meas-tech.net/10/2129/2017/amt-10-2129-2017.pdf |
| _version_ | 1818081553046044672 |
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| author | Y. Blanchard A. Royer N. T. O'Neill D. D. Turner E. W. Eloranta |
| author_facet | Y. Blanchard A. Royer N. T. O'Neill D. D. Turner E. W. Eloranta |
| author_sort | Y. Blanchard |
| collection | DOAJ |
| description | Multiband downwelling thermal measurements of zenith sky radiance,
along with cloud boundary heights, were used in a retrieval algorithm to
estimate cloud optical depth and effective particle diameter of thin ice
clouds in the Canadian High Arctic. Ground-based thermal infrared (IR)
radiances for 150 semitransparent ice clouds cases were acquired at the
Polar Environment Atmospheric Research Laboratory (PEARL) in Eureka, Nunavut,
Canada (80° N, 86° W). We analyzed and quantified the
sensitivity of downwelling thermal radiance to several cloud parameters
including optical depth, effective particle diameter and shape, water vapor
content, cloud geometric thickness and cloud base altitude. A lookup table
retrieval method was used to successfully extract, through an optimal
estimation method, cloud optical depth up to a maximum value of 2.6 and to
separate thin ice clouds into two classes: (1) TIC1 clouds characterized by
small crystals (effective particle diameter ≤ 30 µm), and (2) TIC2 clouds characterized by large ice crystals (effective particle diameter
> 30 µm). The retrieval technique was validated using data from
the Arctic High Spectral Resolution Lidar (AHSRL) and Millimeter Wave Cloud
Radar (MMCR). Inversions were performed over three polar winters and
results showed a significant correlation (<i>R</i><sup>2</sup> = 0.95) for cloud optical
depth retrievals and an overall accuracy of 83 % for the classification of
TIC1 and TIC2 clouds. A partial validation relative to an algorithm based on
high spectral resolution downwelling IR radiance measurements between 8 and
21 µm was also performed. It confirms the robustness of the
optical depth retrieval and the fact that the broadband thermal radiometer
retrieval was sensitive to small particle (TIC1) sizes. |
| first_indexed | 2024-12-10T19:08:02Z |
| format | Article |
| id | doaj.art-7bb21449bfb14d90ace142be0bdf22f0 |
| institution | Directory Open Access Journal |
| issn | 1867-1381 1867-8548 |
| language | English |
| last_indexed | 2024-12-10T19:08:02Z |
| publishDate | 2017-06-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Measurement Techniques |
| spelling | doaj.art-7bb21449bfb14d90ace142be0bdf22f02022-12-22T01:36:50ZengCopernicus PublicationsAtmospheric Measurement Techniques1867-13811867-85482017-06-01102129214710.5194/amt-10-2129-2017Thin ice clouds in the Arctic: cloud optical depth and particle size retrieved from ground-based thermal infrared radiometryY. Blanchard0A. Royer1N. T. O'Neill2D. D. Turner3E. W. Eloranta4Centre d'Applications et de Recherches en Télédétection, Université de Sherbrooke, Sherbrooke, Québec, CanadaCentre d'Applications et de Recherches en Télédétection, Université de Sherbrooke, Sherbrooke, Québec, CanadaCentre d'Applications et de Recherches en Télédétection, Université de Sherbrooke, Sherbrooke, Québec, CanadaGlobal Systems Division, Earth System Research Laboratory, National Oceanic and Atmospheric Administration, Boulder, Colorado, USASpace Science and Engineering Center, University of Wisconsin, Madison, Wisconsin, USAMultiband downwelling thermal measurements of zenith sky radiance, along with cloud boundary heights, were used in a retrieval algorithm to estimate cloud optical depth and effective particle diameter of thin ice clouds in the Canadian High Arctic. Ground-based thermal infrared (IR) radiances for 150 semitransparent ice clouds cases were acquired at the Polar Environment Atmospheric Research Laboratory (PEARL) in Eureka, Nunavut, Canada (80° N, 86° W). We analyzed and quantified the sensitivity of downwelling thermal radiance to several cloud parameters including optical depth, effective particle diameter and shape, water vapor content, cloud geometric thickness and cloud base altitude. A lookup table retrieval method was used to successfully extract, through an optimal estimation method, cloud optical depth up to a maximum value of 2.6 and to separate thin ice clouds into two classes: (1) TIC1 clouds characterized by small crystals (effective particle diameter ≤ 30 µm), and (2) TIC2 clouds characterized by large ice crystals (effective particle diameter > 30 µm). The retrieval technique was validated using data from the Arctic High Spectral Resolution Lidar (AHSRL) and Millimeter Wave Cloud Radar (MMCR). Inversions were performed over three polar winters and results showed a significant correlation (<i>R</i><sup>2</sup> = 0.95) for cloud optical depth retrievals and an overall accuracy of 83 % for the classification of TIC1 and TIC2 clouds. A partial validation relative to an algorithm based on high spectral resolution downwelling IR radiance measurements between 8 and 21 µm was also performed. It confirms the robustness of the optical depth retrieval and the fact that the broadband thermal radiometer retrieval was sensitive to small particle (TIC1) sizes.http://www.atmos-meas-tech.net/10/2129/2017/amt-10-2129-2017.pdf |
| spellingShingle | Y. Blanchard A. Royer N. T. O'Neill D. D. Turner E. W. Eloranta Thin ice clouds in the Arctic: cloud optical depth and particle size retrieved from ground-based thermal infrared radiometry Atmospheric Measurement Techniques |
| title | Thin ice clouds in the Arctic: cloud optical depth and particle size retrieved from ground-based thermal infrared radiometry |
| title_full | Thin ice clouds in the Arctic: cloud optical depth and particle size retrieved from ground-based thermal infrared radiometry |
| title_fullStr | Thin ice clouds in the Arctic: cloud optical depth and particle size retrieved from ground-based thermal infrared radiometry |
| title_full_unstemmed | Thin ice clouds in the Arctic: cloud optical depth and particle size retrieved from ground-based thermal infrared radiometry |
| title_short | Thin ice clouds in the Arctic: cloud optical depth and particle size retrieved from ground-based thermal infrared radiometry |
| title_sort | thin ice clouds in the arctic cloud optical depth and particle size retrieved from ground based thermal infrared radiometry |
| url | http://www.atmos-meas-tech.net/10/2129/2017/amt-10-2129-2017.pdf |
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