NASA Releases New Way to Measure Drought
Read the Official Press Release
While flooding, storms, and fires can all bring disaster, the long-term
wallop delivered by drought can immobilize nations for years, altering
geography, food supplies, access to water, and more.
This week, researchers at NASA's Goddard Space Flight Center are
releasing a new tool for monitoring drought around the world. Using data
collected from the National Oceanographic and Atmospheric Agency's POES
(Polar Orbiting Environmental Satellite), they have developed a drought
index based on plant growth. Used in conjunction with other drought
monitoring and forecasting techniques, this newly released method will
afford experts a sophisticated tool for predicting where droughts could
develop and how long and intensely they might last.
One Year Vegetation Average
-- NDVI Measures Plant Growth
Developed nearly twenty years ago, the Normalized Difference Vegetation
Index (NDVI) is a method for measuring how plants absorb or reflect
sunlight. In these animations, NDVI data gathered by NOAA's Advanced Very
High Resolution Radiometer shows the average annual cycle of vegetation
growth and recession across the whole of the United States and Africa. The
data is averaged over the years 1981 to 2000.
View Movie
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The Cycle of Life on Earth
Although life on Earth moves in regular cycles, each year is not
precisely identical to the next. In these animations, we see several years
of NDVI data moving through seasonal growth and recession. Careful
observation of the scintillating colors will show that although there are
distinct and strong oscillating signals corresponding to the change of
seasons, each year shows unique features as the plants grow and die off. As
we'll see in a few moments, some of these unique features, frozen as still
images, show distinct signs of drought.
View Movie
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The Browning of America
-- Drought Seen from Space
This new drought prediction technique uses a simple bit of visual
arithmetic to derive its results. By taking the NDVI average of a particular
region of the Earth for the years 1981-2000 and subtracting the NDVI value
of that same region during a specific month, we are left with a value that
can be placed along a scale that at one end indicates drought. In the
following images, we see five specific months of data each displayed in
three distinct ways. The first picture in each grouping shows the NDVI
average for the 20 year period in the geographical region being studied. The
second image shows the NDVI measurement for that same region as measured
during a specific month. The final image in each sequence shows the
difference between the two NDVI values; it's essentially a visualization of
the quantified drought anomaly. In the anomaly images, browns indicate
drought conditions as compared to the average, while greens indicate plant
growth greater than the average.
View Movie
View Images and Movies
Recent Drought Indications
20 Year NDVI Average
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NDVI
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NDVI Drought
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North America
July 1981 - 2000 |
North America
July 2000 |
North America
July 2000 |
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Africa
March 1981 - 2000 |
Africa
March 2000 |
Africa
March 2000 |
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Historical Drought Indications
The following groups of images show historical drought data in North America
and Africa.
MODIS: Terra's Tool for
Studying Vegetation
The recent successful activation of NASA's new satellite called Terra
offers researchers a new instrument for building on this drought research.
Called the Moderate-resolution Imaging Spectroradiometer (MODIS) it will be
able to see the specific colors of the world every 1-2 days in 36 spectral
bands. That is, as MODIS begins its full scale operational tour, it will be
able to gather the most regular and highest resolution images of the world's
plant life of any orbiting instrument to date.
For further information, check out the following web sites about drought and
climate research:
Special Thanks to Dr. Compton Tucker
Please give credit for these images to:
NASA - Goddard Space Flight Center
NOAA
Scientific Visualization Studio
Television Production NASA-TV/GSFC
Content Preparation & Project Production:
Michael Starobin
Last Revised: June 28, 2006 at 09:06 AM EDT
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