NASA - National Aeronautics and Space Administration

Image Above: Dust storm approaching Stratford, Texas. Dust bowl surveying in Texas. April 18, 1935 Credit: NOAA Photo Library, Historic NWS collection. More Dust Bowl Images

In 1931, the middle of the U.S. was hit by a long-term drought that brought fear in handfuls of dust. Rain stopped falling from the skies over the Great Plains, and crops died. Then, the "black blizzards" began, as dust from over-plowed and over-grazed fields blew across the land. By late spring of 1934, the Dust Bowl drought was named the worst in our country's history, severely drying out 27 states and three-fourths of the country. By the time it ended in 1939, the U.S. economy had been devastated.

While droughts like this are rare, it is important to understand why they occur. Now, a team of scientists from NASA Goddard Space Flight Center, headed by Siegfried Schubert, have an explanation. In a study published in the March 19th issue of Science, Schubert and colleagues used a NASA computer model developed with modern-era information from satellites to look back and reconstruct the climate of the past 100 years.

The study found cooler than normal tropical Pacific Ocean surface temperatures (blues in image and animation below) combined with warmer tropical Atlantic Ocean temperatures (red-orange in image and animation below) to create conditions in the atmosphere that turned America's breadbasket into a dust bowl for most of the 1930s.

Image Above: Where did the rain go? This animation shows how sea surface temperatures altered weather patterns over the Great Plains. Credit: NASA.

These changes in sea surface 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. This process is shown in the animation on the left.

"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 Niñas 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.

Image Above: Model Simulation: Sea surface temperatures played a strong role in the 1930s dust bowl drought. Credit:NASA.

The research sheds light on how tropical sea surface temperatures can have a remote response and control over weather and climate. The study also helps us understand 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.

For more information about this research and images on the Internet, visit: NASA Goddard Space Flight Center

Krishna Ramanujan
NASA's Goddard Space Flight Center