Mapping liquid water content in snow at the millimeter scale: an intercomparison of mixed-phase optical property models using hyperspectral imaging and in situ measurements
It is well understood that the distribution and quantity of liquid water in snow is relevant for snow hydrology and avalanche forecasting, yet detecting and quantifying liquid water in snow remains a challenge from the micro- to the macro-scale. Using near-infrared (NIR) spectral reflectance measure...
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fttriple:oai:gotriple.eu:oai:doaj.org/article:da9ddc2cb37b4f409d1e19cabbf3a4f1 2023-05-15T18:32:18+02:00 Mapping liquid water content in snow at the millimeter scale: an intercomparison of mixed-phase optical property models using hyperspectral imaging and in situ measurements C. Donahue S. M. Skiles K. Hammonds 2022-01-01 https://doi.org/10.5194/tc-16-43-2022 https://tc.copernicus.org/articles/16/43/2022/tc-16-43-2022.pdf https://doaj.org/article/da9ddc2cb37b4f409d1e19cabbf3a4f1 en eng Copernicus Publications doi:10.5194/tc-16-43-2022 1994-0416 1994-0424 https://tc.copernicus.org/articles/16/43/2022/tc-16-43-2022.pdf https://doaj.org/article/da9ddc2cb37b4f409d1e19cabbf3a4f1 undefined The Cryosphere, Vol 16, Pp 43-59 (2022) geo envir Journal Article https://vocabularies.coar-repositories.org/resource_types/c_6501/ 2022 fttriple https://doi.org/10.5194/tc-16-43-2022 2023-01-22T17:51:29Z It is well understood that the distribution and quantity of liquid water in snow is relevant for snow hydrology and avalanche forecasting, yet detecting and quantifying liquid water in snow remains a challenge from the micro- to the macro-scale. Using near-infrared (NIR) spectral reflectance measurements, previous case studies have demonstrated the capability to retrieve surface liquid water content (LWC) of wet snow by leveraging shifts in the complex refractive index between ice and water. However, different models to represent mixed-phase optical properties have been proposed, including (1) internally mixed ice and water spheres, (2) internally mixed water-coated ice spheres, and (3) externally mixed interstitial ice and water spheres. Here, from within a controlled laboratory environment, we determined the optimal mixed-phase optical property model for simulating wet snow reflectance using a combination of NIR hyperspectral imaging, radiative transfer simulations (Discrete Ordinate Radiative Transfer model, DISORT), and an independent dielectric LWC measurement (SLF Snow Sensor). Maps of LWC were produced by finding the lowest residual between measured reflectance and simulated reflectance in spectral libraries, generated for each model with varying LWC and grain size, and assessed against the in situ LWC sensor. Our results show that the externally mixed model performed the best, retrieving LWC with an uncertainty of ∼1 %, while the simultaneously retrieved grain size better represented wet snow relative to the established scaled band area method. Furthermore, the LWC retrieval method was demonstrated in the field by imaging a snowpit sidewall during melt conditions and mapping LWC distribution in unprecedented detail, allowing for visualization of pooling water and flow features. Article in Journal/Newspaper The Cryosphere Unknown The Cryosphere 16 1 43 59 |
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geo envir C. Donahue S. M. Skiles K. Hammonds Mapping liquid water content in snow at the millimeter scale: an intercomparison of mixed-phase optical property models using hyperspectral imaging and in situ measurements |
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It is well understood that the distribution and quantity of liquid water in snow is relevant for snow hydrology and avalanche forecasting, yet detecting and quantifying liquid water in snow remains a challenge from the micro- to the macro-scale. Using near-infrared (NIR) spectral reflectance measurements, previous case studies have demonstrated the capability to retrieve surface liquid water content (LWC) of wet snow by leveraging shifts in the complex refractive index between ice and water. However, different models to represent mixed-phase optical properties have been proposed, including (1) internally mixed ice and water spheres, (2) internally mixed water-coated ice spheres, and (3) externally mixed interstitial ice and water spheres. Here, from within a controlled laboratory environment, we determined the optimal mixed-phase optical property model for simulating wet snow reflectance using a combination of NIR hyperspectral imaging, radiative transfer simulations (Discrete Ordinate Radiative Transfer model, DISORT), and an independent dielectric LWC measurement (SLF Snow Sensor). Maps of LWC were produced by finding the lowest residual between measured reflectance and simulated reflectance in spectral libraries, generated for each model with varying LWC and grain size, and assessed against the in situ LWC sensor. Our results show that the externally mixed model performed the best, retrieving LWC with an uncertainty of ∼1 %, while the simultaneously retrieved grain size better represented wet snow relative to the established scaled band area method. Furthermore, the LWC retrieval method was demonstrated in the field by imaging a snowpit sidewall during melt conditions and mapping LWC distribution in unprecedented detail, allowing for visualization of pooling water and flow features. |
format |
Article in Journal/Newspaper |
author |
C. Donahue S. M. Skiles K. Hammonds |
author_facet |
C. Donahue S. M. Skiles K. Hammonds |
author_sort |
C. Donahue |
title |
Mapping liquid water content in snow at the millimeter scale: an intercomparison of mixed-phase optical property models using hyperspectral imaging and in situ measurements |
title_short |
Mapping liquid water content in snow at the millimeter scale: an intercomparison of mixed-phase optical property models using hyperspectral imaging and in situ measurements |
title_full |
Mapping liquid water content in snow at the millimeter scale: an intercomparison of mixed-phase optical property models using hyperspectral imaging and in situ measurements |
title_fullStr |
Mapping liquid water content in snow at the millimeter scale: an intercomparison of mixed-phase optical property models using hyperspectral imaging and in situ measurements |
title_full_unstemmed |
Mapping liquid water content in snow at the millimeter scale: an intercomparison of mixed-phase optical property models using hyperspectral imaging and in situ measurements |
title_sort |
mapping liquid water content in snow at the millimeter scale: an intercomparison of mixed-phase optical property models using hyperspectral imaging and in situ measurements |
publisher |
Copernicus Publications |
publishDate |
2022 |
url |
https://doi.org/10.5194/tc-16-43-2022 https://tc.copernicus.org/articles/16/43/2022/tc-16-43-2022.pdf https://doaj.org/article/da9ddc2cb37b4f409d1e19cabbf3a4f1 |
genre |
The Cryosphere |
genre_facet |
The Cryosphere |
op_source |
The Cryosphere, Vol 16, Pp 43-59 (2022) |
op_relation |
doi:10.5194/tc-16-43-2022 1994-0416 1994-0424 https://tc.copernicus.org/articles/16/43/2022/tc-16-43-2022.pdf https://doaj.org/article/da9ddc2cb37b4f409d1e19cabbf3a4f1 |
op_rights |
undefined |
op_doi |
https://doi.org/10.5194/tc-16-43-2022 |
container_title |
The Cryosphere |
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16 |
container_issue |
1 |
container_start_page |
43 |
op_container_end_page |
59 |
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