Retrieval of aerosol components directly from satellite and ground-based measurements
<p>This study presents a novel methodology for the remote monitoring of aerosol components over large spatial and temporal domains. The concept is realized within the GRASP (Generalized Retrieval of Aerosol and Surface Properties) algorithm to directly infer aerosol components from the measure...
| Main Authors: | , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2019-11-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/19/13409/2019/acp-19-13409-2019.pdf |
| Summary: | <p>This study presents a novel methodology for the remote monitoring of aerosol
components over large spatial and temporal domains. The concept is realized
within the GRASP (Generalized Retrieval of Aerosol and Surface Properties)
algorithm to directly infer aerosol components from the measured radiances.
The observed aerosols are assumed to be mixtures of hydrated soluble
particles embedded with black carbon, brown carbon, iron oxide, and other
(non-absorbing) insoluble inclusions. The complex refractive indices of the
dry components are fixed a priori (although the refractive index of the
soluble host is allowed to vary with hydration), and the complex refractive
indices of the mixture are computed using mixing rules. The volume fractions
of these components are derived along with the size distribution and the
fraction of spherical particles, as well as the spectral surface reflectance in
cases when the satellite data are inverted. The retrieval is implemented as a
statistically optimized fit in a continuous space of solutions. This
contrasts with most conventional approaches in which the type of aerosol is
either associated with a pre-assumed aerosol model that is included in a set
of look-up tables, or determined from the analysis of the retrieved aerosol
optical parameters (e.g., single scattering albedo, refractive index, among others, provided by the AERONET retrieval algorithm); here, we retrieve the aerosol
components explicitly. The approach also bridges directly to the quantities
used in global chemical transport models. We first tested the approach with
synthetic data to estimate the uncertainty, and then applied it to real
ground-based AERONET and spaceborne POLDER/PARASOL observations; thus, the
study presents a first attempt to derive aerosol components from satellite observations specifically tied to global chemical transport model quantities. Our results
indicate aerosol optical characteristics that are highly consistent with
standard products (e.g., <span class="inline-formula"><i>R</i></span> of <span class="inline-formula">∼0.9</span> for aerosol optical
thickness) and demonstrate an ability to separate intrinsic optical
properties of fine- and coarse-sized aerosols. We applied our method to
POLDER/PARASOL radiances on the global scale and obtained spatial and
temporal patterns of the aerosol components that agree well with existing
knowledge on aerosol sources and transport features. Finally, we discuss
limitations and perspectives of this new technique.</p> |
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| ISSN: | 1680-7316 1680-7324 |