Measurements and Modeling of Optical-Equivalent Snow Grain Sizes under Arctic Low-Sun Conditions
The size and shape of snow grains directly impacts the reflection by a snowpack. In this article, different approaches to retrieve the optical-equivalent snow grain size (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics&g...
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| Format: | Article |
| Language: | English |
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MDPI AG
2021-12-01
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| Series: | Remote Sensing |
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| Online Access: | https://www.mdpi.com/2072-4292/13/23/4904 |
| _version_ | 1797507189066170368 |
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| author | Evelyn Jäkel Tim Carlsen André Ehrlich Manfred Wendisch Michael Schäfer Sophie Rosenburg Konstantina Nakoudi Marco Zanatta Gerit Birnbaum Veit Helm Andreas Herber Larysa Istomina Linlu Mei Anika Rohde |
| author_facet | Evelyn Jäkel Tim Carlsen André Ehrlich Manfred Wendisch Michael Schäfer Sophie Rosenburg Konstantina Nakoudi Marco Zanatta Gerit Birnbaum Veit Helm Andreas Herber Larysa Istomina Linlu Mei Anika Rohde |
| author_sort | Evelyn Jäkel |
| collection | DOAJ |
| description | The size and shape of snow grains directly impacts the reflection by a snowpack. In this article, different approaches to retrieve the optical-equivalent snow grain size (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>r</mi><mi>opt</mi></msub></semantics></math></inline-formula>) or, alternatively, the specific surface area (SSA) using satellite, airborne, and ground-based observations are compared and used to evaluate ICON-ART (ICOsahedral Nonhydrostatic—Aerosols and Reactive Trace gases) simulations. The retrieval methods are based on optical measurements and rely on the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>r</mi><mi>opt</mi></msub></semantics></math></inline-formula>-dependent absorption of solar radiation in snow. The measurement data were taken during a three-week campaign that was conducted in the North of Greenland in March/April 2018, such that the retrieval methods and radiation measurements are affected by enhanced uncertainties under these low-Sun conditions. An adjusted airborne retrieval method is applied which uses the albedo at 1700 nm wavelength and combines an atmospheric and snow radiative transfer model to account for the direct-to-global fraction of the solar radiation incident on the snow. From this approach, we achieved a significantly improved uncertainty (<25%) and a reduced effect of atmospheric masking compared to the previous method. Ground-based in situ measurements indicated an increase of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>r</mi><mi>opt</mi></msub></semantics></math></inline-formula> of 15 µm within a five-day period after a snowfall event which is small compared to previous observations under similar temperature regimes. ICON-ART captured the observed change of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>r</mi><mi>opt</mi></msub></semantics></math></inline-formula> during snowfall events, but systematically overestimated the subsequent snow grain growth by about 100%. Adjusting the growth rate factor to 0.012 µm<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mrow></mrow><mn>2</mn></msup></semantics></math></inline-formula> s<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mrow></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></semantics></math></inline-formula> minimized the difference between model and observations. Satellite-based and airborne retrieval methods showed higher <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>r</mi><mi>opt</mi></msub></semantics></math></inline-formula> over sea ice (<300 µm) than over land surfaces (<100 µm) which was reduced by data filtering of surface roughness features. Moderate-Resolution Imaging Spectroradiometer (MODIS) retrievals revealed a large spread within a series of subsequent individual overpasses, indicating their limitations in observing the snow grain size evolution in early spring conditions with low Sun. |
| first_indexed | 2024-03-10T04:46:03Z |
| format | Article |
| id | doaj.art-0f55eff534c741599a2f02c52e021d97 |
| institution | Directory Open Access Journal |
| issn | 2072-4292 |
| language | English |
| last_indexed | 2024-03-10T04:46:03Z |
| publishDate | 2021-12-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Remote Sensing |
| spelling | doaj.art-0f55eff534c741599a2f02c52e021d972023-11-23T02:58:09ZengMDPI AGRemote Sensing2072-42922021-12-011323490410.3390/rs13234904Measurements and Modeling of Optical-Equivalent Snow Grain Sizes under Arctic Low-Sun ConditionsEvelyn Jäkel0Tim Carlsen1André Ehrlich2Manfred Wendisch3Michael Schäfer4Sophie Rosenburg5Konstantina Nakoudi6Marco Zanatta7Gerit Birnbaum8Veit Helm9Andreas Herber10Larysa Istomina11Linlu Mei12Anika Rohde13Leipzig Institute for Meteorology (LIM), University of Leipzig, Stephanstr. 3, 04103 Leipzig, GermanyLeipzig Institute for Meteorology (LIM), University of Leipzig, Stephanstr. 3, 04103 Leipzig, GermanyLeipzig Institute for Meteorology (LIM), University of Leipzig, Stephanstr. 3, 04103 Leipzig, GermanyLeipzig Institute for Meteorology (LIM), University of Leipzig, Stephanstr. 3, 04103 Leipzig, GermanyLeipzig Institute for Meteorology (LIM), University of Leipzig, Stephanstr. 3, 04103 Leipzig, GermanyLeipzig Institute for Meteorology (LIM), University of Leipzig, Stephanstr. 3, 04103 Leipzig, GermanyAlfred Wegener Institute Helmholtz Centre for Polar and Marine Research (AWI), 14476 Potsdam, GermanyInstitute of Meteorology and Climate Research, Karlsruhe Institute of Technology (KIT), 76344 Karlsruhe, GermanyAlfred Wegener Institute Helmholtz Centre for Polar and Marine Research (AWI), 27570 Bremerhaven, GermanyAlfred Wegener Institute Helmholtz Centre for Polar and Marine Research (AWI), 27570 Bremerhaven, GermanyAlfred Wegener Institute Helmholtz Centre for Polar and Marine Research (AWI), 27570 Bremerhaven, GermanyAlfred Wegener Institute Helmholtz Centre for Polar and Marine Research (AWI), 27570 Bremerhaven, GermanyInstitute of Environmental Physics, University of Bremen, 28359 Bremen, GermanyInstitute of Meteorology and Climate Research, Karlsruhe Institute of Technology (KIT), 76344 Karlsruhe, GermanyThe size and shape of snow grains directly impacts the reflection by a snowpack. In this article, different approaches to retrieve the optical-equivalent snow grain size (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>r</mi><mi>opt</mi></msub></semantics></math></inline-formula>) or, alternatively, the specific surface area (SSA) using satellite, airborne, and ground-based observations are compared and used to evaluate ICON-ART (ICOsahedral Nonhydrostatic—Aerosols and Reactive Trace gases) simulations. The retrieval methods are based on optical measurements and rely on the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>r</mi><mi>opt</mi></msub></semantics></math></inline-formula>-dependent absorption of solar radiation in snow. The measurement data were taken during a three-week campaign that was conducted in the North of Greenland in March/April 2018, such that the retrieval methods and radiation measurements are affected by enhanced uncertainties under these low-Sun conditions. An adjusted airborne retrieval method is applied which uses the albedo at 1700 nm wavelength and combines an atmospheric and snow radiative transfer model to account for the direct-to-global fraction of the solar radiation incident on the snow. From this approach, we achieved a significantly improved uncertainty (<25%) and a reduced effect of atmospheric masking compared to the previous method. Ground-based in situ measurements indicated an increase of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>r</mi><mi>opt</mi></msub></semantics></math></inline-formula> of 15 µm within a five-day period after a snowfall event which is small compared to previous observations under similar temperature regimes. ICON-ART captured the observed change of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>r</mi><mi>opt</mi></msub></semantics></math></inline-formula> during snowfall events, but systematically overestimated the subsequent snow grain growth by about 100%. Adjusting the growth rate factor to 0.012 µm<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mrow></mrow><mn>2</mn></msup></semantics></math></inline-formula> s<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mrow></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></semantics></math></inline-formula> minimized the difference between model and observations. Satellite-based and airborne retrieval methods showed higher <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>r</mi><mi>opt</mi></msub></semantics></math></inline-formula> over sea ice (<300 µm) than over land surfaces (<100 µm) which was reduced by data filtering of surface roughness features. Moderate-Resolution Imaging Spectroradiometer (MODIS) retrievals revealed a large spread within a series of subsequent individual overpasses, indicating their limitations in observing the snow grain size evolution in early spring conditions with low Sun.https://www.mdpi.com/2072-4292/13/23/4904snow grain sizeSSAArcticairborne observationsMODISSentinel |
| spellingShingle | Evelyn Jäkel Tim Carlsen André Ehrlich Manfred Wendisch Michael Schäfer Sophie Rosenburg Konstantina Nakoudi Marco Zanatta Gerit Birnbaum Veit Helm Andreas Herber Larysa Istomina Linlu Mei Anika Rohde Measurements and Modeling of Optical-Equivalent Snow Grain Sizes under Arctic Low-Sun Conditions Remote Sensing snow grain size SSA Arctic airborne observations MODIS Sentinel |
| title | Measurements and Modeling of Optical-Equivalent Snow Grain Sizes under Arctic Low-Sun Conditions |
| title_full | Measurements and Modeling of Optical-Equivalent Snow Grain Sizes under Arctic Low-Sun Conditions |
| title_fullStr | Measurements and Modeling of Optical-Equivalent Snow Grain Sizes under Arctic Low-Sun Conditions |
| title_full_unstemmed | Measurements and Modeling of Optical-Equivalent Snow Grain Sizes under Arctic Low-Sun Conditions |
| title_short | Measurements and Modeling of Optical-Equivalent Snow Grain Sizes under Arctic Low-Sun Conditions |
| title_sort | measurements and modeling of optical equivalent snow grain sizes under arctic low sun conditions |
| topic | snow grain size SSA Arctic airborne observations MODIS Sentinel |
| url | https://www.mdpi.com/2072-4292/13/23/4904 |
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