Aerosol Properties Computed from Aircraft-Based Observations during the ACE-Asia Campaign: 1. Aerosol Size Distributions Retrieved from Optical Thickness Measurements

Authors

M. Kuzmanoski, University of New South Wales, Sydney, AustraliaFollow
M. A. Box, University of New South Wales, Sydney, Australia
G. P. Box, University of New South Wales, Sydney, Australia
B. Schmid, Bay Area Environmental Research Institute, Sonoma, California, USA
J. Wang, Brookhaven National Laboratory, Upton, New York, USA
P. B. Russell, NASA Ames Research Center, Moffett Field, California, USA
H. H. Jonsson, Center for Interdisciplinary Remotely-Piloted Aircraft Studies, Marina, California, USA
J. H. Seinfield, Department of Chemical Engineering, California Institute of Technology, Pasadena, California, USA

Date of this Version

2007

Citation

Aerosol Science and Technology, 41:202–216, 2007

Comments

U.S. Government Work

Abstract

In this article, aerosol size distributions retrieved from aerosol layer optical thickness spectra, derived from the 14-channel NASA Ames Airborne Tracking Sunphotometer (AATS-14) measurements during the ACE-Asia campaign, are presented. Focusing on distinct aerosol layers (with different particle characteristics) observed in four vertical profiles, we compare the results of two different retrieval methods: constrained linear inversion and a nonlinear least squares method. While the former does not use any assumption about the analytical form of the size distribution, the latter was used to retrieve parameters of a bimodal lognormal size distribution. Furthermore, comparison of the retrieved size distributions with those measured in-situ, aboard the same aircraft on which the sunphotometer was flown, was carried out. Results of the two retrieval methods showed good agreement in the radius ranges from ~0.1 μm to ~1.2–2.0 μm, close to the range of retrievable size distributions from the AATS-14 measurements. In this radius interval, shapes of retrieved and measured size distributions were similar, in accord with close wavelength dependencies of the corresponding optical thicknesses. Additionally, the effect of a size-resolved refractive index on the retrieved size spectra was investigated in selected cases. Retrieval using a constant refractive index pertaining to particle sizes within the range of retrievable size distributions resulted in a size distribution very close to the one retrieved using a size-resolved refractive index.