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Published February 2007 | public
Journal Article

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


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 non-linear 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.

Additional Information

This work was carried out while one author (M. K.) was supported by an International Postgraduate Research Scholarship, funded by the Australian Department of Education, Science and Training (DEST). The authors wish to thank the anonymous reviewer for very useful comments and suggestions.

Additional details

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