On the spectral depolarisation and lidar ratio of mineral dust provided in the AERONET version 3 inversion product

Abstract. Knowledge of the particle lidar ratio (Sλ) and the particle linear depolarisation ratio (δλ) for different aerosol types allows for aerosol typing and aerosol-type separation in lidar measurements. Reference values generally originate from dedicated lidar observations but might also be obtained from the inversion of AErosol RObotic NETwork (AERONET) sun/sky radiometer measurements. This study investigates the consistency of spectral Sλ and δλ provided in the recently released AERONET version 3 inversion product for observations of undiluted mineral dust in the vicinity of the following major deserts: Gobi, Sahara, Arabian, Great Basin, and Great Victoria. Pure dust conditions are identified by an Ångström exponent <0.4 and a fine-mode fraction <0.1. The values of spectral Sλ are found to vary for the different source regions but generally show an increase with decreasing wavelength. The feature correlates to AERONET, retrieving an increase in the imaginary part of the refractive index with decreasing wavelength. The smallest values of Sλ=35–45 sr are found for mineral dust from the Great Basin desert, while the highest values of 50–70 sr have been inferred from AERONET observations of Saharan dust. Values of Sλ at 675, 870, and 1020 nm seem to be in reasonable agreement with available lidar observations, while those at 440 nm are up to 10 sr higher than the lidar reference. The spectrum of δλ shows a maximum of 0.26–0.31 at 1020 nm and decreasing values as wavelength decreases. AERONET-derived δλ values at 870 and 1020 nm are in line with the lidar reference, while values of 0.19–0.24 at 440 nm are smaller than the independent lidar observations by a difference of 0.03 to 0.08. This general behaviour is consistent with earlier studies based on AERONET version 2 products.

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On the spectral depolarisation and lidar ratio of mineral dust provided in the AERONET version 3 inversion product

10.5194/acp-2018-401 ◽

2018 ◽

Author(s):

Sung-Kyun Shin ◽

Matthias Tesche ◽

Kwanchul Kim ◽

Maria Kezoudi ◽

Boyan Tatarov ◽

...

Keyword(s):

Great Basin ◽

Reference Values ◽

Mineral Dust ◽

Depolarisation Ratio ◽

Abstract Knowledge ◽

Lidar Measurements ◽

Lidar Ratio ◽

Aerosol Types ◽

Lidar Observations ◽

Aerosol Type

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First triple-wavelength lidar observations of depolarization and extinction-to-backscatter ratios of Saharan dust

Atmospheric Chemistry and Physics ◽

10.5194/acp-22-355-2022 ◽

2022 ◽

Vol 22 (1) ◽

pp. 355-369

Author(s):

Moritz Haarig ◽

Albert Ansmann ◽

Ronny Engelmann ◽

Holger Baars ◽

Carlos Toledano ◽

...

Keyword(s):

Wavelength Dependence ◽

Saharan Dust ◽

Depolarization Ratio ◽

Shape Model ◽

Lidar Measurements ◽

Fine Mode ◽

Lidar Ratio ◽

Linear Depolarization Ratio ◽

Dust Case ◽

Lidar Observations

Abstract. Two layers of Saharan dust observed over Leipzig, Germany, in February and March 2021 were used to provide the first-ever lidar measurements of the dust lidar ratio (extinction-to-backscatter ratio) and linear depolarization ratio at all three classical lidar wavelengths (355, 532 and 1064 nm). The pure-dust conditions during the first event exhibit lidar ratios of 47 ± 8, 50 ± 5 and 69 ± 14 sr and particle linear depolarization ratios of 0.242 ± 0.024, 0.299 ± 0.018 and 0.206 ± 0.010 at wavelengths of 355, 532 and 1064 nm, respectively. The second, slightly polluted-dust case shows a similar spectral behavior of the lidar and depolarization ratio with values of the lidar ratio of 49 ± 4, 46 ± 5 and 57 ± 9 sr and the depolarization ratio of 0.174 ± 0.041, 0.298 ± 0.016 and 0.242 ± 0.007 at 355, 532 and 1064 nm, respectively. The results were compared with Aerosol Robotic Network (AERONET) version 3 (v3) inversion solutions and the Generalized Retrieval of Aerosol and Surface Properties (GRASP) at six and seven wavelengths. Both retrieval schemes make use of a spheroid shape model for mineral dust. The spectral slope of the lidar ratio from 532 to 1064 nm could be well reproduced by the AERONET and GRASP retrieval schemes. Higher lidar ratios in the UV were retrieved by AERONET and GRASP. The enhancement was probably caused by the influence of fine-mode pollution particles in the boundary layer which are included in the columnar photometer measurements. Significant differences between the measured and retrieved wavelength dependence of the particle linear depolarization ratio were found. The potential sources for these uncertainties are discussed.

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Evaluation of the Lidar/Radiometer Inversion Code (LIRIC) to determine microphysical properties of volcanic and desert dust

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-6-911-2013 ◽

2013 ◽

Vol 6 (1) ◽

pp. 911-948 ◽

Cited By ~ 4

Author(s):

J. Wagner ◽

A. Ansmann ◽

U. Wandinger ◽

P. Seifert ◽

A. Schwarz ◽

...

Keyword(s):

Theoretical Background ◽

Saharan Dust ◽

Dust Particles ◽

Raman Lidar ◽

Particle Volume ◽

Microphysical Properties ◽

Fine Mode ◽

Lidar Ratio ◽

Lidar Observations ◽

Good Agreement

Abstract. The Lidar/Radiometer Inversion Code (LIRIC) combines the multiwavelength lidar technique with sun-sky photometry and allows us to retrieve vertical profiles of particle optical and microphysical properties, separately for fine-mode and coarse-mode particles. After a brief presentation of the theoretical background, we evaluate the potential of LIRIC to retrieve the optical and microphysical properties of irregularly shaped dust particles. The method is applied to two very different aerosol scenarios, a strong Saharan dust outbreak towards central Europe and an Eyjafjallajökull volcanic dust event. LIRIC profiles of particle volume and mass concentrations are compared with results obtained with the polarization-lidar-based POLIPHON method. LIRIC profiles of optical properties such as particle backscatter coefficients, lidar ratio, Ångström exponent, and particle depolarization ratio are compared with direct Raman lidar observations. Good agreement between the different results are found for most of the retrieval products.

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Lidar Ratio Derived for Pure Dust Aerosols: Multi-Year Micro Pulse Lidar Observations in a Saharan Dust-Influenced Region

EPJ Web of Conferences ◽

10.1051/epjconf/201611923017 ◽

2016 ◽

Vol 119 ◽

pp. 23017 ◽

Cited By ~ 2

Author(s):

Carmen Córdoba-Jabonero ◽

José Antonio Adame ◽

James R. Campbell ◽

Emilio Cuevas ◽

Juan Pedro Díaz ◽

...

Keyword(s):

Saharan Dust ◽

Dust Aerosols ◽

Lidar Ratio ◽

Micro Pulse Lidar ◽

Lidar Observations

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Optical properties of different aerosol types: seven years of combined Raman-elastic backscatter lidar measurements in Thessaloniki, Greece

Atmospheric Measurement Techniques ◽

10.5194/amt-3-569-2010 ◽

2010 ◽

Vol 3 (3) ◽

pp. 569-578 ◽

Cited By ~ 60

Author(s):

E. Giannakaki ◽

D. S. Balis ◽

V. Amiridis ◽

C. Zerefos

Keyword(s):

Saharan Dust ◽

Downward Movement ◽

Angstrom Exponent ◽

Lidar Measurements ◽

Ångström Exponent ◽

Lidar Ratio ◽

Local Path ◽

Aerosol Types ◽

Lidar Observations ◽

Ångstrom Exponent

Abstract. We present our combined Raman/elastic backscatter lidar observations which were carried out at the EARLINET station of Thessaloniki, Greece, during the period 2001–2007. The largest optical depths are observed for Saharan dust and smoke aerosol particles. For local and continental polluted aerosols the measurements indicate high aerosol loads. However, measurements associated with the local path indicate enhanced aerosol load within the Planetary Boundary Layer. The lowest value of aerosol optical depth is observed for continental aerosols, from West directions with less free tropospheric contribution. The largest lidar ratios, of the order of 70 sr, are found for biomass burning aerosols. A significant and distinct correlation between lidar ratio and backscatter related Ångström exponent values were estimated for different aerosol categories. Scatter plot between lidar ratio values and Ångström exponent values for local and continental polluted aerosols does not show a significant correlation, with a large variation in both parameters possibly due to variable absorption characteristics of these aerosols. Finally for continental aerosols with west and northwest directions that follow downward movement when arriving at our site constantly low lidar ratios almost independent of size are found.

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Optical properties of different aerosol types: seven years of combined Raman- elastic backscatter lidar measurements in Thessaloniki, Greece

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-2-3027-2009 ◽

2009 ◽

Vol 2 (6) ◽

pp. 3027-3054

Author(s):

E. Giannakaki ◽

D. S. Balis ◽

V. Amiridis ◽

C. Zerefos

Keyword(s):

Saharan Dust ◽

Scatter Plot ◽

Angstrom Exponent ◽

Lidar Measurements ◽

Ångström Exponent ◽

Lidar Ratio ◽

Local Path ◽

Aerosol Types ◽

Lidar Observations ◽

Ångstrom Exponent

Abstract. We present our combined Raman/elastic backscatter lidar observations which were carried out at the EARLINET station of Thessaloniki, Greece, during the period 2001–2007. The largest optical depths are observed for Saharan dust and smoke aerosol loads. For "local" and "continental polluted" aerosols the measurements indicate moderate aerosol loads. However, measurements associated with the "local" path show lower values of free tropospheric contribution (37% versus 46% for "continental polluted") and thus, enhanced aerosol load within the Planetary Boundary Layer. The lowest value of aerosol optical depth is observed for "continental clean" aerosols. The largest lidar ratios, of the order of 70 sr are found for biomass burning aerosols. A significant and distinct correlation between lidar ratio and backscatter related Ångström exponent values was estimated for well defined aerosol categories, which provides a statistical measure of the lidar ratio's dependency on aerosol-size, which is a useful tool for elastic lidar systems. Scatter plot between lidar ratio values and Ångström exponent values for "local" and "continental polluted" aerosols does not show a significant correlation, with a large variation in both parameters possibly due to variable absorption characteristics of these aerosols. Finally for "clean continental" aerosols we found constantly low lidar ratios almost independent of size.

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Ship-borne aerosol profiling with lidar over the Atlantic Ocean: From pure marine conditions to complex dust-smoke mixtures

10.5194/acp-2018-54 ◽

2018 ◽

Author(s):

Stephanie Bohlmann ◽

Holger Baars ◽

Martin Radenz ◽

Ronny Engelmann ◽

Andreas Macke

Keyword(s):

Optical Properties ◽

Atlantic Ocean ◽

Saharan Dust ◽

Marine Aerosol ◽

Angstrom Exponent ◽

The Third ◽

Depolarisation Ratio ◽

Ångström Exponent ◽

Lidar Ratio ◽

Ångstrom Exponent

Abstract. The multiwavelength Raman lidar PollyXT have been regularly operated aboard the research vessel Polarstern on expeditions across the Atlantic Ocean from North to South and vice versa. The lidar measurements of the Polarstern cruises PS95 from Bremerhaven to Cape Town (November 2015) and PS98 from Punta Arenas to Bremerhaven (April/May 2016) are presented and analysed in detail. The latest setup of PollyXT allows improved coverage of the marine boundary layer (MBL) due to an additional near-range receiver. Three case studies provide an overview of the detected aerosol over the Atlantic Ocean. In the first case, marine conditions were observed near South Africa on the autumn cruise PS95. Values of optical properties (depolarisation ratios close to zero, lidar ratios of 23 sr at 355 nm and 532 nm) within the MBL indicate pure marine aerosol. A layer of dried marine aerosol, indicated by an increase of the particle depolarisation ratio to about 10 % at both wavelengths and thus confirming the non-sphericity of these particles, could be detected on the top the MBL. On the same cruise, an almost pure Saharan dust plume was observed near the Canary Islands, presented in the second case. The third case deals with several layers of Saharan dust partly mixed with biomass-burning smoke measured on PS98 near the Cape Verde Islands. While the MBL was partly mixed with dust in the pure Saharan dust case, an almost marine MBL was observed in the third case. A statistical analysis showed latitudinal differences in the optical properties within the MBL, caused by the down-mixing of dust in the tropics and anthropogenic influences in the northern latitudes whereas the optical properties of the MBL in the southern hemisphere correlate with typical marine values. The particle depolarisation ratio of dried marine layers ranged between 4–9 %. Night measurements from PS95 and PS98 were used to illustrate the potential of aerosol classification using lidar ratio, particle depolarisation ratio and Ångström exponent. Lidar ratio and particle depolarisation ratio have been found to be the main indicator for the particle type, whereas the Ångström exponent is rather variable.

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First triple-wavelength lidar observations of depolarization and extinction-to-backscatter ratios of Saharan dust

10.5194/acp-2021-608 ◽

2021 ◽

Author(s):

Moritz Haarig ◽

Albert Ansmann ◽

Ronny Engelmann ◽

Holger Baars ◽

Dietrich Althausen ◽

...

Keyword(s):

Saharan Dust ◽

Depolarization Ratio ◽

Spectral Slope ◽

Desert Dust ◽

Lidar Measurements ◽

Lidar Ratio ◽

Linear Depolarization Ratio ◽

First Time ◽

Dust Case ◽

Lidar Observations

Abstract. Two Saharan dust layers observed over Leipzig in February and March 2021 were used to provide the first ever lidar measurements of the extinction coefficient at 1064 nm for desert dust. The advanced multiwavelength Raman polarization lidar was able to provide, for the first time, the lidar ratio (extinction-to-backscatter ratio) and particle linear depolarization ratio at all three classical lidar wavelengths (355, 532 and 1064 nm). The pure dust conditions during the first event exhibit lidar ratios of 47±8, 50±5 and 63±13 sr and particle linear depolarization ratios of 0.260±0.026, 0.298±0.017 and 0.214±0.025 at the wavelengths of 355, 532 and 1064 nm, respectively. The second, slightly polluted dust case shows a similar spectral behavior with values of the lidar ratio of 52±8, 47±5 and 61±10 sr and the depolarization ratio of 0.188±0.053, 0.270±0.017 and 0.242±0.007 at 355, 532 and 1064 nm, respectively. The results were compared to AERONET v3 inversions and GRASP retrievals at six and seven wavelengths, which could reproduce the spectral slope of the lidar ratio from 532 to 1064 nm. The spectral slope of the particle linear depolarization ratio could not be reproduced by the AERONET inversions, especially at 1064 nm.

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Airborne high spectral resolution lidar observation of pollution aerosol during EUCAARI-LONGREX

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-12-26843-2012 ◽

2012 ◽

Vol 12 (10) ◽

pp. 26843-26869

Author(s):

S. Groß ◽

M. Esselborn ◽

F. Abicht ◽

M. Wirth ◽

A. Fix ◽

...

Keyword(s):

Spatial Distribution ◽

Spectral Resolution ◽

High Spectral Resolution ◽

Mean Values ◽

Lidar Observation ◽

Depolarisation Ratio ◽

Lidar Ratio ◽

High Spectral Resolution Lidar ◽

Lidar Observations ◽

532 Nm

Abstract. Airborne high spectral resolution lidar observations over Europe during the EUCAARI field experiment in May 2008 are analysed with respect to spatial distribution and optical properties of continental pollution aerosol. Continental aerosol is characterized by its depolarisation and lidar ratio. Mean values of 6%±1% for the particle linear depolarisation ratio, and 56 sr±6 sr for the lidar ratio were found for pollution aerosol. Both, lidar ratio and depolarisation ratio at 532 nm show virtually no variations for all analysed days during the measurement campaign.

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Ship-borne aerosol profiling with lidar over the Atlantic Ocean: from pure marine conditions to complex dust–smoke mixtures

Atmospheric Chemistry and Physics ◽

10.5194/acp-18-9661-2018 ◽

2018 ◽

Vol 18 (13) ◽

pp. 9661-9679 ◽

Cited By ~ 13

Author(s):

Stephanie Bohlmann ◽

Holger Baars ◽

Martin Radenz ◽

Ronny Engelmann ◽

Andreas Macke

Keyword(s):

South Africa ◽

Optical Properties ◽

Atlantic Ocean ◽

Saharan Dust ◽

Marine Aerosol ◽

The Third ◽

Depolarisation Ratio ◽

Ångström Exponent ◽

Lidar Ratio ◽

532 Nm

Abstract. The multi-wavelength Raman lidar PollyXT has been regularly operated aboard the research vessel Polarstern on expeditions across the Atlantic Ocean from north to south and vice versa. The lidar measurements of the RV Polarstern cruises PS95 from Bremerhaven, Germany, to Cape Town, Republic of South Africa (November 2015), and PS98 from Punta Arenas, Chile, to Bremerhaven, Germany (April/May 2016), are presented and analysed in detail. The latest set-up of PollyXT allows improved coverage of the marine boundary layer (MBL) due to an additional near-range receiver. Three case studies provide an overview of the aerosol detected over the Atlantic Ocean. In the first case, marine conditions were observed near South Africa on the autumn cruise PS95. Values of optical properties (depolarisation ratios close to zero, lidar ratios of 23 sr at 355 and 532 nm) within the MBL indicate pure marine aerosol. A layer of dried marine aerosol, indicated by an increase of the particle depolarisation ratio to about 10 % at 355 nm (9 % at 532 nm) and thus confirming the non-sphericity of these particles, could be detected on top of the MBL. On the same cruise, an almost pure Saharan dust plume was observed near the Canary Islands, presented in the second case. The third case deals with several layers of Saharan dust partly mixed with biomass-burning smoke measured on PS98 near the Cabo Verde islands. While the MBL was partly mixed with dust in the pure Saharan dust case, an almost marine MBL was observed in the third case. A statistical analysis showed latitudinal differences in the optical properties within the MBL, caused by the down-mixing of dust in the tropics and anthropogenic influences in the northern latitudes, whereas the optical properties of the MBL in the Southern Hemisphere correlate with typical marine values. The particle depolarisation ratio of dried marine layers ranged between 4 and 9 % at 532 nm. Night measurements from PS95 and PS98 were used to illustrate the potential of aerosol classification using lidar ratio, particle depolarisation ratio at 355 and 532 nm, and Ångström exponent. Lidar ratio and particle depolarisation ratio have been found to be the main indicator for particle type, whereas the Ångström exponent is rather variable.

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