Benefit of depolarization ratio at λ = 1064 nm for the retrieval of the aerosol microphysics from lidar measurements
A better quantification of aerosol properties is required for improving the modelling of aerosol effects on weather and climate. This task is methodologically demanding due to the diversity of the microphysical properties of aerosols and the complex relation between their microphysical and optic...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2014-11-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://www.atmos-meas-tech.net/7/3773/2014/amt-7-3773-2014.pdf |
| _version_ | 1819064752339419136 |
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| author | J. Gasteiger V. Freudenthaler |
| author_facet | J. Gasteiger V. Freudenthaler |
| author_sort | J. Gasteiger |
| collection | DOAJ |
| description | A better quantification of aerosol properties is required for improving the
modelling of aerosol effects on weather and climate. This task is
methodologically demanding due to the diversity of the microphysical
properties of aerosols and the complex relation between their microphysical
and optical properties. Advanced lidar systems provide spatially and
temporally resolved information on the aerosol optical properties that is
sufficient for the retrieval of important aerosol microphysical properties.
Recently, the mass concentration of transported volcanic ash, which is
relevant for the flight safety of aeroplanes, was retrieved from measurements
of such lidar systems in southern Germany. The relative uncertainty of the
retrieved mass concentration was on the order of ±50%.
<br><br>
The present study investigates improvements of the retrieval accuracy when
the capability of measuring the linear depolarization ratio at 1064 nm is
added to the lidar setup. The lidar setups under investigation are based on
those of MULIS and POLIS of the Ludwig-Maximilians-Universität in
Munich (Germany) which measure the linear depolarization ratio at 355 and
532 nm with high accuracy. The improvements are determined by comparing
uncertainties from retrievals applied to simulated measurements of this lidar
setup with uncertainties obtained when the depolarization at 1064 nm is
added to this setup. The simulated measurements are based on real lidar
measurements of transported Eyjafjallajökull volcano ash. It is found that
additional 1064 nm depolarization measurements significantly reduce the
uncertainty of the retrieved mass concentration and effective particle size.
This significant improvement in accuracy is the result of the increased
sensitivity of the lidar setup to larger particles. The size dependence of
the depolarization does not vary strongly with refractive index, thus we
expect similar benefits for the retrieval in case of measurements of other volcanic ash
compositions and also for transported desert dust. For the retrieval of the
single scattering albedo, which is relevant to the radiative transfer in
aerosol layers, no significant improvements were found. |
| first_indexed | 2024-12-21T15:35:34Z |
| format | Article |
| id | doaj.art-ad968e744b6d49e4b0672083f03e3c45 |
| institution | Directory Open Access Journal |
| issn | 1867-1381 1867-8548 |
| language | English |
| last_indexed | 2024-12-21T15:35:34Z |
| publishDate | 2014-11-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Measurement Techniques |
| spelling | doaj.art-ad968e744b6d49e4b0672083f03e3c452022-12-21T18:58:39ZengCopernicus PublicationsAtmospheric Measurement Techniques1867-13811867-85482014-11-0173773378110.5194/amt-7-3773-2014Benefit of depolarization ratio at λ = 1064 nm for the retrieval of the aerosol microphysics from lidar measurementsJ. Gasteiger0V. Freudenthaler1Meteorologisches Institut, Ludwig-Maximilians-Universität, Munich, GermanyMeteorologisches Institut, Ludwig-Maximilians-Universität, Munich, GermanyA better quantification of aerosol properties is required for improving the modelling of aerosol effects on weather and climate. This task is methodologically demanding due to the diversity of the microphysical properties of aerosols and the complex relation between their microphysical and optical properties. Advanced lidar systems provide spatially and temporally resolved information on the aerosol optical properties that is sufficient for the retrieval of important aerosol microphysical properties. Recently, the mass concentration of transported volcanic ash, which is relevant for the flight safety of aeroplanes, was retrieved from measurements of such lidar systems in southern Germany. The relative uncertainty of the retrieved mass concentration was on the order of ±50%. <br><br> The present study investigates improvements of the retrieval accuracy when the capability of measuring the linear depolarization ratio at 1064 nm is added to the lidar setup. The lidar setups under investigation are based on those of MULIS and POLIS of the Ludwig-Maximilians-Universität in Munich (Germany) which measure the linear depolarization ratio at 355 and 532 nm with high accuracy. The improvements are determined by comparing uncertainties from retrievals applied to simulated measurements of this lidar setup with uncertainties obtained when the depolarization at 1064 nm is added to this setup. The simulated measurements are based on real lidar measurements of transported Eyjafjallajökull volcano ash. It is found that additional 1064 nm depolarization measurements significantly reduce the uncertainty of the retrieved mass concentration and effective particle size. This significant improvement in accuracy is the result of the increased sensitivity of the lidar setup to larger particles. The size dependence of the depolarization does not vary strongly with refractive index, thus we expect similar benefits for the retrieval in case of measurements of other volcanic ash compositions and also for transported desert dust. For the retrieval of the single scattering albedo, which is relevant to the radiative transfer in aerosol layers, no significant improvements were found.https://www.atmos-meas-tech.net/7/3773/2014/amt-7-3773-2014.pdf |
| spellingShingle | J. Gasteiger V. Freudenthaler Benefit of depolarization ratio at λ = 1064 nm for the retrieval of the aerosol microphysics from lidar measurements Atmospheric Measurement Techniques |
| title | Benefit of depolarization ratio at λ = 1064 nm for the retrieval of the aerosol microphysics from lidar measurements |
| title_full | Benefit of depolarization ratio at λ = 1064 nm for the retrieval of the aerosol microphysics from lidar measurements |
| title_fullStr | Benefit of depolarization ratio at λ = 1064 nm for the retrieval of the aerosol microphysics from lidar measurements |
| title_full_unstemmed | Benefit of depolarization ratio at λ = 1064 nm for the retrieval of the aerosol microphysics from lidar measurements |
| title_short | Benefit of depolarization ratio at λ = 1064 nm for the retrieval of the aerosol microphysics from lidar measurements |
| title_sort | benefit of depolarization ratio at λ 1064 nm for the retrieval of the aerosol microphysics from lidar measurements |
| url | https://www.atmos-meas-tech.net/7/3773/2014/amt-7-3773-2014.pdf |
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