Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Moist soil ’hot spots’ may affect rainfall


While the Earth is moistened by rainfall, scientists believe that the water in soil can, in turn, influence rainfall both regionally and globally. Forecasters, water resource managers and farmers may benefit once this connection is better understood.

A NASA researcher led an effort that used a dozen computer models to locate "hot spots" around the world where soil moisture may strongly affect rainfall during northern hemisphere summertime. The results appear in the August 20 issue of Science Magazine.

The "hot spots" appear in the central plains of North America, the Sahel, equatorial Africa, and India. Less intense hot spots show up in South America, central Asia and China. These hot spots are, in a sense, analogous to ocean areas where sea surface temperatures strongly affect climate and weather, the most famous example being in the eastern tropical Pacific, where El Ninos occur.

"The study arguably provides the best estimate ever of the areas where soil moisture changes can affect rainfall," said Randal Koster, a researcher at NASA’s Goddard Space Flight Center in Greenbelt, Md. Koster led the international computer modeling effort in collaboration with Paul Dirmeyer and Zhichang Guo of the Center for Ocean Land Atmosphere Studies, Calverton, Md.

In the Global Land-Atmosphere Coupling Experiment (GLACE), Koster and colleagues duplicated the same experiment using 12 different computer models from around the world. With each model researchers compared the rainfall behavior in two sets of simulations: one in which the soil moisture differed between the simulations, and one in which all simulations saw the same soil moisture. Any increase in rainfall agreement in the second set of simulations shows an impact of soil moisture on the rainfall.

Although the model results differed, the simulations also shared certain common features. By averaging together all the findings, the researchers identified the common features, or "hot spots" where soil moisture influences rainfall the most.

If soil moisture is assumed to affect rain locally, the hot spots tell researchers who study land and atmosphere interactions where to focus their measurements. NASA helps in the design of satellites and instruments to measure soil moisture. Currently, the Advanced Microwave Scanning Radiometer for EOS on NASA’s Aqua satellite measures the moisture in surface soil down to a depth of a few centimeters. In 2009, NASA plans to launch the Hydrosphere State (HYDROS) mission that will provide the first global view of the Earth’s changing soil moisture down to 5 centimeters.

However, even if researchers could observe global soil moisture levels at depths greater than a few centimeters, it would be very hard to tell from the data alone how this moisture contributes to precipitation. There are too many factors involved. "Computer models are notorious for their limitations. Still, given the overwhelming difficulty of finding the hot spots through direct measurement, our study provides the next best thing: a multi-model estimate of their locations," Koster said.

In general, the hot spots have one thing in common: they occur in transition zones between wet and dry regions. This was expected. In wet climates, the Sun’s energy and cloudiness play a bigger role in determining evaporation rates than soil moisture. In dry climates, the limited water leads to limited evaporation rates, that are simply too small to have a large impact on the atmosphere. The fact that satellites cannot measure soil moisture through very dense vegetation is therefore less of a problem. Dense vegetation appears in wet regions, where the hot spots are typically not found.

Understanding soil moisture levels and their connection to precipitation has important implications. It may improve seasonal forecasting of rainfall vital to water managers, as well as improve the accuracy of short-term weather forecasts. Interest in the study is therefore high at national weather centers, like the National Centers for Environmental Prediction (NCEP), Camp Springs, Md.

"At NCEP, we are working on ways to specify soil moisture accurately, in order to take advantage of the type of connections examined in GLACE," said co-author Kenneth Mitchell of NCEP. NCEP’s soil moisture estimation project, known as the Land Data Assimilation System, is run in collaboration with scientists at NASA. Institutions from the United States, Canada, the United Kingdom, Japan, and Australia each funded use of their own model.

Krishna Ramanujan | EurekAlert!
Further information:

More articles from Earth Sciences:

nachricht Gas hydrate research: Advanced knowledge and new technologies
23.03.2018 | Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum GFZ

nachricht New technologies and computing power to help strengthen population data
22.03.2018 | University of Southampton

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Space observation with radar to secure Germany's space infrastructure

Satellites in near-Earth orbit are at risk due to the steady increase in space debris. But their mission in the areas of telecommunications, navigation or weather forecasts is essential for society. Fraunhofer FHR therefore develops radar-based systems which allow the detection, tracking and cataloging of even the smallest particles of debris. Satellite operators who have access to our data are in a better position to plan evasive maneuvers and prevent destructive collisions. From April, 25-29 2018, Fraunhofer FHR and its partners will exhibit the complementary radar systems TIRA and GESTRA as well as the latest radar techniques for space observation across three stands at the ILA Berlin.

The "traffic situation" in space is very tense: the Earth is currently being orbited not only by countless satellites but also by a large volume of space...

Im Focus: Researchers Discover New Anti-Cancer Protein

An international team of researchers has discovered a new anti-cancer protein. The protein, called LHPP, prevents the uncontrolled proliferation of cancer cells in the liver. The researchers led by Prof. Michael N. Hall from the Biozentrum, University of Basel, report in “Nature” that LHPP can also serve as a biomarker for the diagnosis and prognosis of liver cancer.

The incidence of liver cancer, also known as hepatocellular carcinoma, is steadily increasing. In the last twenty years, the number of cases has almost doubled...

Im Focus: Researchers at Fraunhofer monitor re-entry of Chinese space station Tiangong-1

In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.

Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...

Im Focus: Alliance „OLED Licht Forum“ – Key partner for OLED lighting solutions

Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.

They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...

Im Focus: Mars' oceans formed early, possibly aided by massive volcanic eruptions

Oceans formed before Tharsis and evolved together, shaping climate history of Mars

A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

New solar solutions for sustainable buildings and cities

23.03.2018 | Event News

Virtual reality conference comes to Reutlingen

19.03.2018 | Event News

Ultrafast Wireless and Chip Design at the DATE Conference in Dresden

16.03.2018 | Event News

Latest News

For graphite pellets, just add elbow grease

23.03.2018 | Materials Sciences

Unique communication strategy discovered in stem cell pathway controlling plant growth

23.03.2018 | Agricultural and Forestry Science

Sharpening the X-ray view of the nanocosm

23.03.2018 | Physics and Astronomy

Science & Research
Overview of more VideoLinks >>>