Start of the Green Season and Normalized Difference Vegetation Index in Alaska’s Arctic National Parks
Daily Normalized Difference Vegetation Index (NDVI) values from the MODIS Aqua and Terra satellites were compared with on-the-ground camera observations at five locations in northern Alaska. Over half of the spring rise in NDVI was due to the transition from the snow-covered landscape to the snow-fr...
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ftmdpi:oai:mdpi.com:/2072-4292/13/13/2554/ 2023-08-20T04:04:19+02:00 Start of the Green Season and Normalized Difference Vegetation Index in Alaska’s Arctic National Parks David K. Swanson agris 2021-06-30 application/pdf https://doi.org/10.3390/rs13132554 EN eng Multidisciplinary Digital Publishing Institute Remote Sensing in Agriculture and Vegetation https://dx.doi.org/10.3390/rs13132554 https://creativecommons.org/licenses/by/4.0/ Remote Sensing; Volume 13; Issue 13; Pages: 2554 Alaska Arctic greenness NDVI phenology tundra Text 2021 ftmdpi https://doi.org/10.3390/rs13132554 2023-08-01T02:04:51Z Daily Normalized Difference Vegetation Index (NDVI) values from the MODIS Aqua and Terra satellites were compared with on-the-ground camera observations at five locations in northern Alaska. Over half of the spring rise in NDVI was due to the transition from the snow-covered landscape to the snow-free surface prior to the deciduous leaf-out. In the fall after the green season, NDVI fluctuated between an intermediate level representing senesced vegetation and lower values representing clouds and intermittent snow, and then dropped to constant low levels after establishment of the permanent winter snow cover. The NDVI value of snow-free surfaces after fall leaf senescence was estimated from multi-year data using a 90th percentile smoothing spline curve fit to a plot of daily NDVI values vs. ordinal date. This curve typically showed a flat region of intermediate NDVI values in the fall that represent cloud- and snow-free days with senesced vegetation. This “fall plateau” was readily identified in a large systematic sample of MODIS NDVI values across the study area, in typical tundra, shrub, and boreal forest environments. The NDVI level of the fall plateau can be extrapolated to the spring rising leg of the annual NDVI curve to approximate the true start of green season. Text Arctic Tundra Alaska MDPI Open Access Publishing Arctic Remote Sensing 13 13 2554 |
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Open Polar |
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MDPI Open Access Publishing |
op_collection_id |
ftmdpi |
language |
English |
topic |
Alaska Arctic greenness NDVI phenology tundra |
spellingShingle |
Alaska Arctic greenness NDVI phenology tundra David K. Swanson Start of the Green Season and Normalized Difference Vegetation Index in Alaska’s Arctic National Parks |
topic_facet |
Alaska Arctic greenness NDVI phenology tundra |
description |
Daily Normalized Difference Vegetation Index (NDVI) values from the MODIS Aqua and Terra satellites were compared with on-the-ground camera observations at five locations in northern Alaska. Over half of the spring rise in NDVI was due to the transition from the snow-covered landscape to the snow-free surface prior to the deciduous leaf-out. In the fall after the green season, NDVI fluctuated between an intermediate level representing senesced vegetation and lower values representing clouds and intermittent snow, and then dropped to constant low levels after establishment of the permanent winter snow cover. The NDVI value of snow-free surfaces after fall leaf senescence was estimated from multi-year data using a 90th percentile smoothing spline curve fit to a plot of daily NDVI values vs. ordinal date. This curve typically showed a flat region of intermediate NDVI values in the fall that represent cloud- and snow-free days with senesced vegetation. This “fall plateau” was readily identified in a large systematic sample of MODIS NDVI values across the study area, in typical tundra, shrub, and boreal forest environments. The NDVI level of the fall plateau can be extrapolated to the spring rising leg of the annual NDVI curve to approximate the true start of green season. |
format |
Text |
author |
David K. Swanson |
author_facet |
David K. Swanson |
author_sort |
David K. Swanson |
title |
Start of the Green Season and Normalized Difference Vegetation Index in Alaska’s Arctic National Parks |
title_short |
Start of the Green Season and Normalized Difference Vegetation Index in Alaska’s Arctic National Parks |
title_full |
Start of the Green Season and Normalized Difference Vegetation Index in Alaska’s Arctic National Parks |
title_fullStr |
Start of the Green Season and Normalized Difference Vegetation Index in Alaska’s Arctic National Parks |
title_full_unstemmed |
Start of the Green Season and Normalized Difference Vegetation Index in Alaska’s Arctic National Parks |
title_sort |
start of the green season and normalized difference vegetation index in alaska’s arctic national parks |
publisher |
Multidisciplinary Digital Publishing Institute |
publishDate |
2021 |
url |
https://doi.org/10.3390/rs13132554 |
op_coverage |
agris |
geographic |
Arctic |
geographic_facet |
Arctic |
genre |
Arctic Tundra Alaska |
genre_facet |
Arctic Tundra Alaska |
op_source |
Remote Sensing; Volume 13; Issue 13; Pages: 2554 |
op_relation |
Remote Sensing in Agriculture and Vegetation https://dx.doi.org/10.3390/rs13132554 |
op_rights |
https://creativecommons.org/licenses/by/4.0/ |
op_doi |
https://doi.org/10.3390/rs13132554 |
container_title |
Remote Sensing |
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13 |
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13 |
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2554 |
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