NASA scientists have an explanation for one of the worst
climatic events in the history of the United States, the “Dust
Bowl” drought, which devastated the Great Plains and all but
dried up an already depressed American economy in the 1930’s.
Siegfried Schubert of NASA’s Goddard Space Flight Center,
Greenbelt, Md., and colleagues used a computer model developed
with modern-era satellite data to look at the climate over the
past 100 years. The study found cooler than normal tropical
Pacific Ocean surface temperatures combined with warmer
tropical Atlantic Ocean temperatures to create conditions in
the atmosphere that turned America’s breadbasket into a dust
bowl from 1931 to 1939. The team’s data is in this week’s
Science magazine.
These changes in sea surface temperatures created shifts in the
large-scale weather patterns and low level winds that reduced
the normal supply of moisture from the Gulf of Mexico and
inhibited rainfall throughout the Great Plains.
“The 1930s drought was the major climatic event in the nation’s
history,” Schubert said. “Just beginning to understand what
occurred is really critical to understanding future droughts
and the links to global climate change issues we’re
experiencing today,” he said.
By discovering the causes behind U.S. droughts, especially
severe episodes like the Plains’ dry spell, scientists may
recognize and possibly foresee future patterns that could
create similar conditions. For example, La Ninas are marked by
cooler than normal tropical Pacific Ocean surface water
temperatures, which impact weather globally, and also create
dry conditions over the Great Plains.
The researchers used NASA’s Seasonal-to-Interannual Prediction
Project (NSIPP) atmospheric general circulation model and
agency computational facilities to conduct the research. The
NSIPP model was developed using NASA satellite observations,
including; Clouds and the Earth’s Radiant Energy System
radiation measurements; and the Global Precipitation
Climatology Project precipitation data.
The model showed cooler than normal tropical Pacific Ocean
temperatures and warmer than normal tropical Atlantic Ocean
temperatures contributed to a weakened low-level jet stream and
changed its course. The jet stream, a ribbon of fast moving air
near the Earth’s surface, normally flows westward over the Gulf
of Mexico and then turns northward pulling up moisture and
dumping rain onto the Great Plains. As the low level jet stream
weakened, it traveled farther south than normal. The Great
Plains dried up and dust storms formed.
The research shed light on how tropical sea surface
temperatures can have a remote response and control over
weather and climate. It also confirmed droughts can become
localized based on soil moisture levels, especially during
summer. When rain is scarce and soil dries, there is less
evaporation, which leads to even less precipitation, creating a
feedback process that reinforces lack of rainfall.
The study also shed light on droughts throughout the 20th
century. Analysis of other major U.S. droughts of the 1900s
suggests a cool tropical Pacific was a common factor. Schubert
said simulating major events like the 1930s drought provides an
excellent test for computer models. While the study finds no
indication of a similar Great Plains drought in the near
future, it is vital to continue studies relating to climate
change. NASA’s current and planned suite of satellite sensors
is uniquely poised to answer related climate questions.
NASA’s Earth Science Enterprise funded the study. The
Enterprise is dedicated to understanding the Earth as an
integrated system and applying Earth System Science to improve
climate, weather, and natural hazard prediction using the
unique vantage point of space. For information about NASA and
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