AGU Journal highlights -- May 6, 2009

Title: Aerosol effects on liquid-water path of thin stratocumulus clouds

Authors: Seoung Soo Lee and Joyce E. Penner: Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, Ann Arbor, Michigan, U.S.A.;

Stephen M. Saleeby: Department of Atmospheric Science, Colorado State University, Fort Collins, Colorado, U.S.A.

Source: Journal of Geophysical Research-Atmospheres (JGR-D) paper 10.1029/2008JD010513, 2009; http://dx.doi.org/10.1029/2008JD010513

8. Differences in mineral dust flakes influence how solar radiation scatters

Mineral dust, an important aerosol type in the Earth's atmosphere, scatters incoming solar radiation. This scattering causes uncertainties to climate models and skews remote sensing observations. To learn more about exactly how mineral dust scatters solar radiation, Nousiainen et al. study the morphology and composition of particles obtained from the Sahara desert. Using electron microscope imaging, X-ray diffractometry, and energy-dispersive spectroscopy, the authors find that thin flakes composed of calcite and dolomite were abundant in the samples collected. These minerals are of particular interest due to their strong double refraction (birefringence). Through comparing their scattering properties with other particles, the authors find that such a strong birefringence has a substantial and systematic impact on the particles' ability to scatter solar radiation back to space. They also find that the commonly used models for mineral dust—spherical and spheroidal particles—were unsuccessful in predicting their scattering properties. The authors conclude that excluding the shape and the birefringence of dust particles could cause errors in assessing the direct aerosol effect in climate models.

Title: Single-scattering modeling of thin, birefringent mineral-dust flakes using the discrete-dipole approximation

Authors: Timo Nousiainen: Department of Physics, University of Helsinki, Helsinki, Finland;

Evgenij Zubko: Center for Atmospheric and Oceanic Studies, Tohoku University, Sendai, Japan; also at Astronomical Institute of Kharkov National University, Kharkov, Ukraine;

Jarkko V. Niemi: Department of Biological and environmental Sciences, University of Helsinki, Helsinki, Finland;

Kaarle Kupiainen: Finnish Environment Institute, Helsinki, Finland;

Martti Lehtinen: Geological Museum, University of Helsinki, Helsinki, Finland;

Karri Muinonen: Observatory, University of Helsinki, Helsinki, Finland;

Gorden Videen: Army Research Laboratory, Adelphi, Maryland, U.S.A.

Source: Journal of Geophysical Research-Atmospheres (JGR-D) paper 10.1029/2008JD011564, 2009; http://dx.doi.org/10.1029/2008JD011564

9. Global warming may turn forests into carbon sources