Mapping Snow Grain Size over Greenland from MODIS
This paper presents a new automatic algorithm to derive optical snow grain size (SGS) at 1 km resolution using Moderate Resolution Imaging Spectroradiometer (MODIS) measurements. Differently from previous approaches, snow grains are not assumed to be spherical but a fractal approach is used to accou...
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ftnasantrs:oai:casi.ntrs.nasa.gov:20080038648 2023-05-15T16:27:18+02:00 Mapping Snow Grain Size over Greenland from MODIS Tedesco, Marco Lyapustin, Alexei Wang, Yujie Kokhanovsky, Alexander Unclassified, Unlimited, Publicly available [2008] application/pdf http://hdl.handle.net/2060/20080038648 unknown Document ID: 20080038648 http://hdl.handle.net/2060/20080038648 Copyright, Distribution as joint owner in the copyright CASI Meteorology and Climatology 2008 ftnasantrs 2018-06-09T22:59:19Z This paper presents a new automatic algorithm to derive optical snow grain size (SGS) at 1 km resolution using Moderate Resolution Imaging Spectroradiometer (MODIS) measurements. Differently from previous approaches, snow grains are not assumed to be spherical but a fractal approach is used to account for their irregular shape. The retrieval is conceptually based on an analytical asymptotic radiative transfer model which predicts spectral bidirectional snow reflectance as a function of the grain size and ice absorption. The analytical form of solution leads to an explicit and fast retrieval algorithm. The time series analysis of derived SGS shows a good sensitivity to snow metamorphism, including melting and snow precipitation events. Preprocessing is performed by a Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm, which includes gridding MODIS data to 1 km resolution, water vapor retrieval, cloud masking and an atmospheric correction. MAIAC cloud mask (CM) is a new algorithm based on a time series of gridded MODIS measurements and an image-based rather than pixel-based processing. Extensive processing of MODIS TERRA data over Greenland shows a robust performance of CM algorithm in discrimination of clouds over bright snow and ice. As part of the validation analysis, SGS derived from MODIS over selected sites in 2004 was compared to the microwave brightness temperature measurements of SSM\I radiometer, which is sensitive to the amount of liquid water in the snowpack. The comparison showed a good qualitative agreement, with both datasets detecting two main periods of snowmelt. Additionally, MODIS SGS was compared with predictions of the snow model CROCUS driven by measurements of the automatic whether stations of the Greenland Climate Network. We found that CROCUS grain size is on average a factor of two larger than MODIS-derived SGS. Overall, the agreement between CROCUS and MODIS results was satisfactory, in particular before and during the first melting period in mid-June. Following detailed time series analysis of SGS for four permanent sites, the paper presents SGS maps over the Greenland ice sheet for the March-September period of 2004. Other/Unknown Material Greenland Ice Sheet NASA Technical Reports Server (NTRS) Greenland |
institution |
Open Polar |
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NASA Technical Reports Server (NTRS) |
op_collection_id |
ftnasantrs |
language |
unknown |
topic |
Meteorology and Climatology |
spellingShingle |
Meteorology and Climatology Tedesco, Marco Lyapustin, Alexei Wang, Yujie Kokhanovsky, Alexander Mapping Snow Grain Size over Greenland from MODIS |
topic_facet |
Meteorology and Climatology |
description |
This paper presents a new automatic algorithm to derive optical snow grain size (SGS) at 1 km resolution using Moderate Resolution Imaging Spectroradiometer (MODIS) measurements. Differently from previous approaches, snow grains are not assumed to be spherical but a fractal approach is used to account for their irregular shape. The retrieval is conceptually based on an analytical asymptotic radiative transfer model which predicts spectral bidirectional snow reflectance as a function of the grain size and ice absorption. The analytical form of solution leads to an explicit and fast retrieval algorithm. The time series analysis of derived SGS shows a good sensitivity to snow metamorphism, including melting and snow precipitation events. Preprocessing is performed by a Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm, which includes gridding MODIS data to 1 km resolution, water vapor retrieval, cloud masking and an atmospheric correction. MAIAC cloud mask (CM) is a new algorithm based on a time series of gridded MODIS measurements and an image-based rather than pixel-based processing. Extensive processing of MODIS TERRA data over Greenland shows a robust performance of CM algorithm in discrimination of clouds over bright snow and ice. As part of the validation analysis, SGS derived from MODIS over selected sites in 2004 was compared to the microwave brightness temperature measurements of SSM\I radiometer, which is sensitive to the amount of liquid water in the snowpack. The comparison showed a good qualitative agreement, with both datasets detecting two main periods of snowmelt. Additionally, MODIS SGS was compared with predictions of the snow model CROCUS driven by measurements of the automatic whether stations of the Greenland Climate Network. We found that CROCUS grain size is on average a factor of two larger than MODIS-derived SGS. Overall, the agreement between CROCUS and MODIS results was satisfactory, in particular before and during the first melting period in mid-June. Following detailed time series analysis of SGS for four permanent sites, the paper presents SGS maps over the Greenland ice sheet for the March-September period of 2004. |
author |
Tedesco, Marco Lyapustin, Alexei Wang, Yujie Kokhanovsky, Alexander |
author_facet |
Tedesco, Marco Lyapustin, Alexei Wang, Yujie Kokhanovsky, Alexander |
author_sort |
Tedesco, Marco |
title |
Mapping Snow Grain Size over Greenland from MODIS |
title_short |
Mapping Snow Grain Size over Greenland from MODIS |
title_full |
Mapping Snow Grain Size over Greenland from MODIS |
title_fullStr |
Mapping Snow Grain Size over Greenland from MODIS |
title_full_unstemmed |
Mapping Snow Grain Size over Greenland from MODIS |
title_sort |
mapping snow grain size over greenland from modis |
publishDate |
2008 |
url |
http://hdl.handle.net/2060/20080038648 |
op_coverage |
Unclassified, Unlimited, Publicly available |
geographic |
Greenland |
geographic_facet |
Greenland |
genre |
Greenland Ice Sheet |
genre_facet |
Greenland Ice Sheet |
op_source |
CASI |
op_relation |
Document ID: 20080038648 http://hdl.handle.net/2060/20080038648 |
op_rights |
Copyright, Distribution as joint owner in the copyright |
_version_ |
1766016436241694720 |