AGU journal highlights -- Dec. 3, 2010

December 03, 2010

The following highlights summarize research papers that have been recently published in Geophysical Research Letters (GRL).

In this release:

  1. Population trends, not climate, causing increased flood fatalities in Africa
  2. Earth's lakes warming in response to climate change
  3. Ozone hole affects upper-atmosphere temperature and circulation
  4. Solar wind contains more oxygen than previously thought
  5. Predicting variability in radiation belt dynamics
  6. Iron oxide observed in Earth's airglow

Anyone may read the scientific abstract for any already-published paper by clicking on the link provided at the end of each Highlight. You can also read the abstract by going to and inserting into the search engine the full doi (digital object identifier), e.g. 10.1029/2010GL045467. The doi is found at the end of each Highlight below.

Journalists and public information officers (PIOs) at educational or scientific institutions, who are registered with AGU, also may download papers cited in this release by clicking on the links below. Instructions for members of the news media, PIOs, and the public for downloading or ordering the full text of any research paper summarized below are available at

1. Population trends, not climate, causing increased flood fatalities in Africa

Flood-related fatalities in Africa have increased greatly over the past several decades. Has the intensity of flooding increased, perhaps owing to global climate changes? Or have human activity, population growth, and development patterns led to increased human vulnerability? To find out, Di Baldassarre et al. analyze large data sets of floods in Africa. The authors consider trends in flooding as well as population dynamics and land use changes. They find that the magnitude and frequency of African floods have not increased significantly during the past century, but increased unplanned human settlements in flood-prone areas have been a major factor in increasing the risk of fatalities and economic damage. They suggest that settlements in flood-prone areas should be discouraged. Early warning systems could also help reduce fatalities.

See 15 October related blog post:

Title: Flood fatalities in Africa: From diagnosis to mitigation

Authors: Giuliano Di Baldassarre: Department of Hydroinformatics and Knowledge Management, UNESCO-IHE, Delft, Netherlands;

Alberto Montanari: DISTART, University of Bologna, Bologna, Italy;

Harry Lins: U.S. Geological Survey, Reston, Virginia, USA;

Demetris Koutsoyiannis: Department of Water Resources, National Technical University of Athens, Athens, Greece;

Luigia Brandimarte: Department of Water Engineering, UNESCO-IHE, Delft, Netherlands;

Günter Blöschl: Institute for Hydraulic and Water Resources Engineering, Vienna University of Technology, Vienna, Austria.

Source: Geophysical Research Letters, doi:10.1029/2010GL045467, 2010

2. Earth's lakes warming in response to climate change

Many studies of global climate have used air temperature measurements to characterize recent warming trends. A new study shows that inland water bodies such as lakes and wetlands have also been warming steadily in recent decades. Schneider and Hook analyze satellite nighttime thermal infrared imagery of 167 large inland water bodies around the world during the period 1985-2009. They find that mean nighttime surface water temperature for these inland water bodies has been rising at an average rate of about 0.045 degrees Celsius (0.081 degrees Fahrenheit ) per year, with rates as high as 0.1 degrees Celsius (0.18 degrees Fahrenheit) per year in some places. The greatest warming has taken place in the mid and high latitudes of the Northern Hemisphere, and in some regions, water temperature warmed faster than regional air temperature. The researchers suggest that the study provides a new data source for assessing the effects of climate change.

See 23 November press release:

Title: Space observations of inland water bodies show rapid surface warming since 1985

Authors: Philipp Schneider and Simon J. Hook: Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA.

Source: Geophysical Research Letters, doi:10.1029/2010GL045059, 2010

3. Ozone hole affects upper-atmosphere temperature and circulation

Observations have shown differences in altitude and brightness between polar mesospheric clouds (clouds made of ice crystals in the upper mesosphere) in the Northern Hemisphere and those in the Southern Hemisphere. Various mechanisms have been suggested to explain the differences; a new study shows that the ozone hole in the stratosphere above Antarctica could be playing a key role in the temperature and circulation patterns in the mesosphere (an atmospheric layer that begins 50 kilometers above Earth's surface, just above the stratosphere), leading to differences in polar mesospheric clouds.

Using climate model simulations, Smith et al. show that the ozone hole causes a decrease in temperature in the lower stratosphere that persists into the summer. These temperature changes are accompanied by wind changes that modify the upward propagation of small-scale waves, which in turn alter the atmospheric circulation in the mesosphere in the Southern Hemisphere.

The researchers find that the hemispheric asymmetry was small before 1980 but increased at about the same time as the onset of the ozone hole. A model run with no ozone loss showed no increases in the hemispheric asymmetry in mesospheric circulation and temperature, confirming that ozone loss is a likely cause of the hemispheric differences. They suggest that as the ozone hole recovers in upcoming decades, these trends in mesospheric temperature and circulation may change.

Title: Simulations of the response of mesospheric circulation and temperature to the Antarctic ozone hole

Authors: Anne K. Smith, Rolando R. Garcia, Daniel R. Marsh, and Douglas E. Kinnison: Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, Colorado, USA;

Jadwiga H. Richter: Chemistry and Global Dynamics, National Center for Atmospheric Research, Boulder, Colorado, USA.

Source: Geophysical Research Letters, doi:10.1029/2010GL045255, 2010

4. Solar wind contains more oxygen than previously thought

Oxygen is abundant in the Sun, yet the solar oxygen abundance has not been measured with high accuracy. Von Steiger et al. use long-term solar wind data from the Ulysses spacecraft to measure the flux of oxygen ions, the flux of protons, and the ratio of the two. The new measurements suggest that the solar oxygen abundance may be slightly higher than other recent studies have found. An accurate value for the solar oxygen abundance is important for interpreting helioseismological analyses and for understanding the chemical evolution of the galaxy and solar system.

Title: Oxygen flux in the solar wind: Ulysses observations

Authors: Rudolf von Steiger: International Space Science Institute, Bern, Switzerland;

Thomas H. Zurbuchen: Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor, Michigan, USA;

David J. McComas: Space Science and Engineering Division, Southwest Research Institute, San Antonio, Texas, USA; and Department of Physics and Astronomy, University of Texas at San Antonio, San Antonio, Texas, USA.

Source: Geophysical Research Letters, doi:10.1029/2010GL045389, 2010

5. Predicting variability in radiation belt dynamics

In Earth's outer radiation belt the flux of energetic electrons and ions can vary significantly over short time periods in response to solar activity. These energetic particles can damage satellites, making it important to be able to understand and predict variability in the radiation belts. In recent years, scientists' understanding of how electrons are accelerated in the radiation belts has changed. Thorne reviews a variety of recent advances in understanding and modeling radiation belt dynamics, highlighting the importance of interactions of energetic particles with magnetosphere waves.

Title: Radiation belt dynamics: The importance of wave-particle interactions

Author: Richard Mansergh Thorne: Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, California, USA.

Source: Geophysical Research Letters, doi:10.1029/2010GL044990, 2010

6. Iron oxide observed in Earth's airglow

Earth's night airglow, a weak emission of light caused by chemical reactions in the planet's atmosphere, has been studied for more than a century. Because iron is common in meteorites that deposit debris in Earth's atmosphere, it was expected that iron oxide (FeO) would be found in the airglow, but it had not been detected until now. Evans et al. report observations made using the Optical Spectrograph and Infrared Imager System on the Odin spacecraft that show orange bands at about 600 nanometers in the night airglow spectrum. Comparison with published laboratory measurements of FeO emission spectra indicate that the observed orange bands in the airglow are probably due to FeO. The researchers suggest that the orange band FeO emission is probably produced through interactions of iron with ozone in the atmosphere.

Title: Discovery of the FeO orange bands in the terrestrial night airglow spectrum obtained with OSIRIS on the Odin spacecraft

Authors: W. F. J. Evans: NorthWest Research Associates, Inc., Redmond, Washington, USA; and Centre for Research in Earth and Space Science, York University, Toronto, Ontario, Canada;

R. L. Gattinger, D. A. Degenstein and E. J. Llewellyn: ISAS, Department of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, Saskatchewan, Canada;

T. G. Slanger and D. V. Saran: Molecular Physics Laboratory, SRI International, Menlo Park, California, USA.

Source: Geophysical Research Letters, doi:10.1029/2010GL045310, 2010

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