November 15, 2021 - Fall in the Appalachian Mountains
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As temperatures dropped and sunshine shortened across the Appalachian
Mountains in early November 2021, the forests of the Appalachian
Mountains burst into breathtaking autumn color. The Moderate Resolution
Imaging Spectroradiometer (MODIS) on board NASA’s Aqua satellite
acquired this true-color image on November 8.
The ridges and valleys of the Appalachians seen in this image curve
from eastern West Virginia (top right) to Georgia (lower left). Most of
the valleys appear bright green, but the deciduous forests at higher
elevations wear a blanket of orange and red. To the west and in the
coastal region east of the Appalachian, broad swaths of gold and
golden-green mark the colors of spent agricultural crops and add to the
beauty of a sunny autumn day.
The magic that spurs the glorious colors of autumn is driven by
chemistry. Green leaves are rich in chlorophyll, a molecule that plants
use to synthesize food. Chlorophyll absorbs the red and blue portions
of sunlight, and so the reflected light—which gives the leaf ifs
color—looks green. Chlorophyll isn’t a very stable compound, so plants
have to continuously make it to keep their leaves green, and they do
this when there is plenty of sunlight and warm temperatures. When
temperatures drop and days shorten, levels of chlorophyll drop as well.
Leaves contain other pigments, depending on the type of tree, such as
carotenoids and anthocyanins. As chlorophyll fades, the other colors
become visible. Carotenoids show up as yellow and anthocyanins appear
red. Each species of tree contains different amounts of pigments, which
makes it possible to generalize what color a given type of tree in the
fall. According to the U.S. Forest Service, Oaks generally turn red,
brown, or russet; aspen and yellow-poplar turn golden. Maples differ by
species. Red maple turns brilliant scarlet; sugar maple, orange-red;
and black maple, yellow. Leaves of some trees, such as elms, simply
become brown.
To visualize the dramatic change that occurred between September 24,
and November 8, the NASA Worldview App allows a comparison of this
region on those two days. To view the comparison, click here.
Image Facts
Satellite: Aqua
Date Acquired: 11/8/2021
Resolutions: 1km (1.5 MB), 500m (3.9 MB), 250m (9.7 MB)
Bands Used:
Image Credit: MODIS Land Rapid Response Team, NASA GSFC
https://modis.gsfc.nasa.gov/gallery/individual.php?db_date=2021-11-15
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