2004 EARTH SCIENCE VIDEOTAPES |
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Tape Title | Record ID | Date Produced | TRT: |
Synopsis |
| NASA GOES BACK IN TIME TO FIND THE SOURCES OF THE 1930S DUST BOWL | G04-014 | 3/19/04 | 14:24 | NASA computer models developed with modernÐera satellite data take scientists back in to time to help them decipher the causes behind the 1930s dust bowl. The study found that sea surface temperatures drove changes in large-scale weather patterns and low level winds that inhibited rainfall throughout the Great Plains. By understanding the causes behind U.S. droughts, especially severe episodes like the 'dust bowl' dry spell, scientists may recognize and possibly forecast patterns in the future that could create similar conditions.
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TAPE CONTENTS: |
| ITEM (1): Changes in The Sea, Changes in The Air - Abnormal sea surface temperatures (SST) in the Pacific and the Atlantic Ocean played a strong role in the 1930s dust bowl drought. Scientists used SST data acquired from old ship records to create starting conditions for the computer models. They let the model run on its own, driven only by the observed monthly global sea surface temperatures. The model was able to reconstruct the Dust Bowl drought quite closely, providing strong evidence that the Great Plains dry spell originated with abnormal sea surface temperatures. .This sequence shows the warmer than normal SST (red-orange) in that the Atlantic Ocean and colder than normal SST (blues) in the Pacific Ocean, followed by a low level jet stream that shifted and weakened reducing the normal supply of moisture to the Great Plains.
Courtesy: NASA
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| ITEM (2): Comparing Model Data to Actual - This video compares model and actual rainfall results. The first image, model data, shows extensive drying throughout the Great Plains. The dark red represents the driest areas, followed by light red, then orange, and yellow, which is the least dry. The second image shows actual rainfall result. The actual results are quite similar to the model results. Courtesy: NASA
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| ITEM (3): Where Did The Rain Go? - This illustration shows how cooler than normal tropical Pacific Ocean temperatures (blues) and warmer than normal tropical Atlantic Ocean temperatures (red and orange) contributed to a weakened low level jet stream and changed its course. The jet stream normally flows westward over the Gulf of Mexico and then turns northward pulling up moisture and dumping rain onto the Great Plains. During the 1930s, this low level jet stream weakened, carrying less moisture, and shifted further south. The Great Plains land dried up and dust storms blew across the U.S.
Courtesy: NASA
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| ITEM (4): Learning From El Nino and La Nina (G99-011) - Much of the research done to understand the effects of El Nino and La Nina have helped scientists understand that tropical sea surface temperatures can have a remote response and control over weather and climate. These satellite images illustrate the dramatic changes in ocean temperatures and sea surface height from the peak of the 1998 El Nino to the peak of the 1999 La Nina. Ocean surface temperatures plummeted 15 degrees (f) and sea elevation dropped two feet in some regions in the eastern Pacific. Red indicates warmer than normal ocean surface temperatures and blue indicates cooler temperatures.
Courtesy: NASA
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| ITEM (5): Divining Data: Constructing New Tools For Studying Climate (G00-083) - Computer models help scientists understand how sea surface temperatures and soil moisture feedbacks impact climate. By comparing simulated events with historical records of climate and weather, they can then make refinements to their models. These models then can be used to make future regional climate predictions as well as help them 'backcast' climate for 100 years.
Green areas indicate regions that the model predicted higher than average quantities of soil moisture; brown areas show places that should have lower levels of soil moisture. The wispy veil curling through the maps depicts water vapor estimates in the atmosphere, an influential component to overall climate behavior.
Courtesy: NASA
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| ITEM (6): Monitoring Dust From Space - NASA satellites observe aerosols and dust all over the world. Scientists have used this data to study how dust impacts rain, coral reefs and air quality around the world.
a. 2001 China Dust Storm moves around the globe ,Total Ozone Mapping Spectrometer (TOMS) instruments (G03-066)
b. 2003 Saharan Dust Storm, Terra and Aqua satellites (G03-008)
Courtesy: NASA
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| ITEM (7): Western Drought (G02-005) - Drought was a major contributor to United States' 2002 record wildfire season. Images created from France's SPOT satellite show the health of vegetation as severely weakened indicating very dry conditions over large areas of the western U.S. There is a strong correlation between the rainfall amount and vegetation "greenness" particularly for semi-arid regions. Severe and persistent below normal vegetation greenness over these regions implies drought. Courtesy: NASA
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| ITEM (8): Looking Up By Looking Down: How Soil Moisture Affects Rainfall (G00-038) - Soil moisture is an important factor for predicting drought. Research has confirmed that droughts can become localized based on soil moisture levels, especially during summer. When rains become scarce, and soils get dry, there is less evaporation, which leads to even less precipitation, creating a feedback process that reinforces lack of rainfall. This feedback process occurred during the 1930s dust bowl and doubled the severity of the drought.
There are two important regions to the atmosphere: the planetary boundary layer, and the atmosphere above it. The boundary layer is the air found directly above the ground. It's a roiling, churning section of the atmosphere, mainly stirred up by friction against the surface of the planet. The atmosphere above it is generally far calmer and colder.
(Caption for side-by-side pix) - In the following pair of animations we see how soil moisture affects rainfall. The first case concerns moist soilÑthe image on the left. The picture on the right goes with our look at dry soil conditions. Courtesy: NASA
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| ITEM (9): An Affinity For Water: Soil Moisture Coaxes Repeated Soakings (G00-083) - Soil moisture is necessary in order to kick-start atmospheric convection during warm months to yield rain. Here, as the Sun heats up the moist ground, temperature climbs and moisture evaporates from the ground, saturating the air. That saturated air mass rises until it breaks through the planetary boundary layer, rushing into the colder, less dense upper atmosphere. The air rapidly cools causing the suspended water vapor to condense, creating thunderclouds. Continued condensation inside those clouds ultimately form droplets that become heavy and fall from the sky as rain. Courtesy: NASA
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| ITEM (10): Dry Spring, Dry Summer: Arid Ground Inhibits Rainfall (G00-083) - Spring and summer seasons that start out dry are likely to remain dry because inadequate soil moisture inhibits the production of rain clouds, rain, evaporation, and condensation.
Here's what happens: dry soil heats up during the day. The planetary boundary layer warms and rises. As it rises, it expands. But without the added energy contained in evaporated moisture, it does not have either enough power to break into the upper regions of the sky, nor enough moisture to condense into rain clouds if it does manage to poke through the boundary layer. In other words, the boundary layer expands as it warms, but rain clouds do not form. Dry conditions at the beginning of the season often mean dry conditions for months.
Courtesy: NASA
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| ITEM (11): Satellites Feed Computer Models Data - The data collected from NASA's Earth Observing Satellites are put into models that help scientists understand the planets changing climate.
a. Terra
b. Aqua
Courtesy: NASA
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| ITEM (12): B-roll - Photographs of the 1930s Dust Bowl: Courtesy: NOAA Photo Library, Historic NWS collection
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| ITEM (13): B-roll of Scientists Interview - Siegfried Schubert, Researcher NASA's Goddard Space Flight Center, Greenbelt, Md
Courtesy: NASA
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Earth Science Gallery