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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| Format: | Article |
| Language: | English |
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MDPI AG
2021-06-01
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| Series: | Remote Sensing |
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| Online Access: | https://www.mdpi.com/2072-4292/13/13/2554 |
| _version_ | 1797528287367397376 |
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| author | David K. Swanson |
| author_facet | David K. Swanson |
| author_sort | David K. Swanson |
| collection | DOAJ |
| 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. |
| first_indexed | 2024-03-10T09:56:04Z |
| format | Article |
| id | doaj.art-bb0e06b738834d84832360d499757d5d |
| institution | Directory Open Access Journal |
| issn | 2072-4292 |
| language | English |
| last_indexed | 2024-03-10T09:56:04Z |
| publishDate | 2021-06-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Remote Sensing |
| spelling | doaj.art-bb0e06b738834d84832360d499757d5d2023-11-22T02:20:01ZengMDPI AGRemote Sensing2072-42922021-06-011313255410.3390/rs13132554Start of the Green Season and Normalized Difference Vegetation Index in Alaska’s Arctic National ParksDavid K. Swanson0Arctic Inventory and Monitoring Network, National Park Service, Fairbanks, AK 99709, USADaily 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.https://www.mdpi.com/2072-4292/13/13/2554AlaskaArcticgreennessNDVIphenologytundra |
| spellingShingle | David K. Swanson Start of the Green Season and Normalized Difference Vegetation Index in Alaska’s Arctic National Parks Remote Sensing Alaska Arctic greenness NDVI phenology tundra |
| title | 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_short | 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 |
| topic | Alaska Arctic greenness NDVI phenology tundra |
| url | https://www.mdpi.com/2072-4292/13/13/2554 |
| work_keys_str_mv | AT davidkswanson startofthegreenseasonandnormalizeddifferencevegetationindexinalaskasarcticnationalparks |