Retrieval of aerosol properties from ceilometer and photometer measurements: long-term evaluation with in situ data and statistical analysis at Montsec (southern Pyrenees)
<p>Given the need for accurate knowledge of aerosol microphysical and optical properties with height resolution, various algorithms combining vertically resolved and column-integrated aerosol information have been developed in the last years. Here we present new results of vertically resolved...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2019-06-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://www.atmos-meas-tech.net/12/3255/2019/amt-12-3255-2019.pdf |
| Summary: | <p>Given the need for accurate knowledge of aerosol
microphysical and optical properties with height resolution, various
algorithms combining vertically resolved and column-integrated aerosol
information have been developed in the last years. Here we present new
results of vertically resolved extensive aerosol optical properties
(backscattering, scattering and extinction) and volume concentrations
retrieved with the GRASP (Generalized Retrieval of Aerosol and Surface
Properties) algorithm over a 3-year period. The range-corrected signal (RCS)
at 1064 nm measured with a ceilometer and the aerosol optical depth (AOD)
and sky radiances from a sun/sky photometer have been used as input for this
algorithm. We perform a detailed evaluation of GRASP retrievals with
simultaneous in situ measurements performed at the same height, at the
Montsec mountaintop observatory (MSA) in the Pre-Pyrenees (northeastern
Spain). This is the first long-term evaluation of various outputs of this
algorithm; previous evaluations focused only on the study of aerosol volume
concentration for short-term periods. In general, our results show good
agreement between techniques although GRASP inversions yield higher values
than those measured in situ. The statistical analysis of the extinction
coefficient vertical profiles shows a clear seasonality as well as
significant differences depending on the air mass origin. The observed
seasonal cycle is mainly modulated by a higher development of the
atmospheric boundary layer (ABL) during warm months, which favors the
transport of pollutants to MSA, and higher influence of regional and
North African episodes. On the other hand, in winter, MSA is frequently
influenced by free-troposphere conditions and venting periods and therefore
lower extinction coefficients that markedly decrease with height. This study
shows the potentiality of implementing GRASP in ceilometer and lidar
networks for obtaining aerosol optical properties and volume concentrations
at multiple sites, which will definitely contribute to enhancing the
representativeness of the aerosol vertical distribution as well as to providing
useful information for satellite and global model evaluation.</p> |
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| ISSN: | 1867-1381 1867-8548 |