AGU Journal Highlights -- March 19, 2008

Title: Atlantic forced component of the Indian monsoon interannual variability

Authors: F. Kucharski and J. H. Yoo: Earth System Physics Section, Abdus Salam International Center for Theoretical Physics, Trieste, Italy;

A. Bracco: School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, U.S.A.;

F. Molteni: European Centre for Medium-Range Weather Forecasts, Reading, U.K.

Source: Geophysical Research Letters (GRL) paper 10.1029/2007GL033037, 2008; http://dx.doi.org/10.1029/2007GL033037

7. Improving measures of wildfire smoke heights from space

The elevation at which wildfire smoke is injected into the atmosphere has a strong influence on how the smoke is dispersed and is a key input into aerosol transport models. Currently, spaceborne lidar studies can constrain the height of smoke plumes with great precision, but horizontal sampling is very poor on large scales. Spaceborne stereo imaging has much greater coverage and captures the cores of major fires, but its ability to constrain the height of the smoke plume is limited to those with discernible features. Noting that data from both imaging techniques can be combined to yield a better picture of smoke transport during a wildfire, Kahn et al. study the fires that occurred in the Alaska-Yukon region during the summer of 2004. The authors find that at least 10 percent of wildfire smoke plumes reached the free troposphere. Because accurate knowledge of smoke transport patterns can help scientists understand the environmental effects of wildfires, the combined strengths of stereo and lidar observations will help scientists better monitor potentially harmful smoke plumes.

Title: Wildfire smoke injection heights: Two perspectives from space

Authors: Ralph A. Kahn: Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, U.S.A.; now at NASA Goddard Space Flight Center, Greenbelt, Maryland, U.S.A.

Yang Chen, Qinbin Li; David J. Diner: Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, U.S.A.;

David L. Nelson: Columbus Technologies and Services, Inc., Pasadena, California, U.S.A.;

Fok-Yan Leung and Jennifer A Logan: School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, U.S.A.

Source: Geophysical Research Letters (GRL) paper 10.1029/2007GL032165, 2008; http://dx.doi.org/10.1029/2007GL032165

8. Examining a link between the Sun’s upper atmosphere and Earth

To help scientists understand the energy budget of the Earth’s mesosphere and lower thermosphere, NASA launched the Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) satellite mission in December 2001. Instruments on TIMED, one of which observes and quantifies the energy budget by measuring the thermosphere’s infrared emissions from radiative cooling and another of which measures ultraviolet energy radiated by the Sun, have now been measuring for more than 5 years. Mlynczak et al. analyze these data streams and find that the infrared and solar time series exhibit a decrease in radiated and absorbed power, consistent with the waning phase of the solar cycle. The infrared time series also exhibits high-frequency variations that are not evident in the solar power time series. Spectral analysis shows a statistically significant 9-day periodicity in the infrared but not the solar data. The authors link these 9-day periodicities to the recurrence of coronal holes on the Sun. These results demonstrate a direct coupling between the upper atmosphere of the Sun and the infrared energy budget of the thermosphere.