Validation of AVHRR- and MODIS-derived albedos of snow and ice surfaces by means of helicopter measurements
We describe the validation of surface albedos of snow and glacier ice as derived from Advanced Very High Resolution Radiometer (AVHRR) and MOderate Resolution Imaging Spectrometer (MODIS) satellite data. For this purpose we measured surface albedos from a helicopter over Vatnajökull, Iceland, and th...
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ftunivutrecht:oai:dspace.library.uu.nl:1874/22693 2023-07-23T04:19:23+02:00 Validation of AVHRR- and MODIS-derived albedos of snow and ice surfaces by means of helicopter measurements Greuell, W. Oerlemans, J. 2005 image/pdf https://dspace.library.uu.nl/handle/1874/22693 en eng 0022-1430 Print 1727-5652 Online https://dspace.library.uu.nl/handle/1874/22693 info:eu-repo/semantics/ClosedAccess Natuur- en Sterrenkunde Article 2005 ftunivutrecht 2023-07-01T23:21:37Z We describe the validation of surface albedos of snow and glacier ice as derived from Advanced Very High Resolution Radiometer (AVHRR) and MOderate Resolution Imaging Spectrometer (MODIS) satellite data. For this purpose we measured surface albedos from a helicopter over Vatnajökull, Iceland, and the Kangerlussuaq transect (western part of the Greenland ice sheet) in Thematic Mapper (TM) bands 2 and 4 and AVHRR bands 1 and 2, and converted these values to 'measured albedos' in three MODIS bands. Relative to other validation methods, our helicopter measurements have the advantages of larger spatial coverage and of (almost) direct measurements in satellite-sensor spectral bands. We found the smallest differences between the satellite-derived and helicopter albedos for the Kangerlussuaq transect: for AVHRR data a mean difference of 0.01 in both bands (with the satellite in near-nadir position) and for two MODIS images a mean difference of 0.00-0.02 for bands 2 and 4, and 0.03 for band 1. For two AVHRR images of Vatnajökull, we found mean differences of up to 0.06. Differences are primarily due to errors in the satellite-derived albedos, which, in turn, are mainly caused by errors in the calibration coefficients of the satellite sensors and insufficient knowledge of the angular distribution of the radiation reflected by snow and ice. Satellite data obtained from view zenith angles larger than ~50-55° appeared to be unsuitable. Article in Journal/Newspaper glacier glacier Greenland Ice Sheet Iceland Kangerlussuaq Vatnajökull Utrecht University Repository Greenland Kangerlussuaq ENVELOPE(-55.633,-55.633,72.633,72.633) Vatnajökull ENVELOPE(-16.823,-16.823,64.420,64.420) |
institution |
Open Polar |
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Utrecht University Repository |
op_collection_id |
ftunivutrecht |
language |
English |
topic |
Natuur- en Sterrenkunde |
spellingShingle |
Natuur- en Sterrenkunde Greuell, W. Oerlemans, J. Validation of AVHRR- and MODIS-derived albedos of snow and ice surfaces by means of helicopter measurements |
topic_facet |
Natuur- en Sterrenkunde |
description |
We describe the validation of surface albedos of snow and glacier ice as derived from Advanced Very High Resolution Radiometer (AVHRR) and MOderate Resolution Imaging Spectrometer (MODIS) satellite data. For this purpose we measured surface albedos from a helicopter over Vatnajökull, Iceland, and the Kangerlussuaq transect (western part of the Greenland ice sheet) in Thematic Mapper (TM) bands 2 and 4 and AVHRR bands 1 and 2, and converted these values to 'measured albedos' in three MODIS bands. Relative to other validation methods, our helicopter measurements have the advantages of larger spatial coverage and of (almost) direct measurements in satellite-sensor spectral bands. We found the smallest differences between the satellite-derived and helicopter albedos for the Kangerlussuaq transect: for AVHRR data a mean difference of 0.01 in both bands (with the satellite in near-nadir position) and for two MODIS images a mean difference of 0.00-0.02 for bands 2 and 4, and 0.03 for band 1. For two AVHRR images of Vatnajökull, we found mean differences of up to 0.06. Differences are primarily due to errors in the satellite-derived albedos, which, in turn, are mainly caused by errors in the calibration coefficients of the satellite sensors and insufficient knowledge of the angular distribution of the radiation reflected by snow and ice. Satellite data obtained from view zenith angles larger than ~50-55° appeared to be unsuitable. |
format |
Article in Journal/Newspaper |
author |
Greuell, W. Oerlemans, J. |
author_facet |
Greuell, W. Oerlemans, J. |
author_sort |
Greuell, W. |
title |
Validation of AVHRR- and MODIS-derived albedos of snow and ice surfaces by means of helicopter measurements |
title_short |
Validation of AVHRR- and MODIS-derived albedos of snow and ice surfaces by means of helicopter measurements |
title_full |
Validation of AVHRR- and MODIS-derived albedos of snow and ice surfaces by means of helicopter measurements |
title_fullStr |
Validation of AVHRR- and MODIS-derived albedos of snow and ice surfaces by means of helicopter measurements |
title_full_unstemmed |
Validation of AVHRR- and MODIS-derived albedos of snow and ice surfaces by means of helicopter measurements |
title_sort |
validation of avhrr- and modis-derived albedos of snow and ice surfaces by means of helicopter measurements |
publishDate |
2005 |
url |
https://dspace.library.uu.nl/handle/1874/22693 |
long_lat |
ENVELOPE(-55.633,-55.633,72.633,72.633) ENVELOPE(-16.823,-16.823,64.420,64.420) |
geographic |
Greenland Kangerlussuaq Vatnajökull |
geographic_facet |
Greenland Kangerlussuaq Vatnajökull |
genre |
glacier glacier Greenland Ice Sheet Iceland Kangerlussuaq Vatnajökull |
genre_facet |
glacier glacier Greenland Ice Sheet Iceland Kangerlussuaq Vatnajökull |
op_relation |
0022-1430 Print 1727-5652 Online https://dspace.library.uu.nl/handle/1874/22693 |
op_rights |
info:eu-repo/semantics/ClosedAccess |
_version_ |
1772182394702397440 |