Distribution, facies, ages, and proposed tectonic associations of regionally metamorphosed rocks in northern Alaska

1989 ◽  
Author(s):  
Cynthia Dusel-Bacon ◽  
William Peters Brosge ◽  
Alison B. Till ◽  
Elizabeth O. Doyle ◽  
Charles F. Mayfield ◽  
...  
Keyword(s):  
Northern Alaska

Stratigraphy, structure, and geologic synthesis of northern Alaska

1992 ◽  
Author(s):  
Thomas E. Moore ◽  
W.K. Wallace ◽  
K.J. Bird ◽  
Susan M. Karl ◽  
C.G. Mull ◽  
...  
Keyword(s):  
Northern Alaska

scholarly journals Start of the Green Season and Normalized Difference Vegetation Index in Alaska’s Arctic National Parks

2021 ◽  
Vol 13 (13) ◽  
pp. 2554
Author(s):  
David K. Swanson
Keyword(s):  
National Parks ◽  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Free Surfaces ◽  
Modis Ndvi ◽  
Curve Fit ◽  
Winter Snow ◽  
Systematic Sample ◽  
Low Levels ◽  
Northern Alaska

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.

scholarly journals Comparison of model-produced active layer fields: Results for northern Alaska

2007 ◽  
Vol 112 (F2) ◽  
Author(s):  
Nikolay I. Shiklomanov ◽  
Oleg A. Anisimov ◽  
Tingjun Zhang ◽  
Sergey Marchenko ◽  
Frederick E. Nelson ◽  
...  
Keyword(s):  
Active Layer ◽  
Northern Alaska
Sign in / Sign up

Export Citation Format

Share Document