Brown Carbon Spheres in East Asian Outflow and Their Optical Properties
Duncan T. L. Alexander,1
Peter A. Crozier,2*
James R. Anderson3
Atmospheric aerosols play a substantial role in climate change
through radiative forcing. Combustion-produced carbonaceous
particles are the main light-absorbing aerosols; thus, quantifying
their optical properties is essential for determining the magnitude
of direct forcing. By using the electron energy-loss spectrum
in the transmission electron microscope, we quantified the optical
properties of individual, submicrometer amorphous carbon spheres
that are ubiquitous in East Asian–Pacific outflow. The
data indicate that these common spheres are brown, not black,
with a mean refractive index of 1.67 – 0.27
i (where
i =
) at a wavelength of 550 nanometers. The results suggest that brown carbon aerosols should
be explicitly included in radiative forcing models.
2 School of Materials, Arizona State University, Post Office Box 878706, Tempe, AZ 85287, USA.
3 Department of Mechanical and Aerospace Engineering, Arizona State University, Post Office Box 876106, Tempe, AZ 85287, USA.
* To whom correspondence should be addressed. E-mail: crozier{at}asi.edu
