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

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.

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

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.

scholarly journals Is Near-Spherical Shape “the New Black” for Smoke ?

2020 ◽  
Vol 237 ◽  
pp. 02017
Author(s):  
Anna Gialitaki ◽  
Alexandra Tsekeri ◽  
Vassilis Amiridis ◽  
Romain Ceolato ◽  
Lucas Paulien ◽  
...  
Keyword(s):  
Spherical Shape ◽  
Wavelength Dependence ◽  
Depolarization Ratio ◽  
Smoke Particles ◽  
Near Ir ◽  
Lidar Measurements ◽  
Lidar Ratio ◽  
T Matrix ◽  
Linear Depolarization Ratio

We present smoke lidar measurements from the Canadian fires of 2017. The advected smoke layers over Europe are detected at both tropospheric and stratospheric heights, with the latter presenting non-typical values of the Particle Linear Depolarization Ratio (PLDR) with strong wavelength dependence from the UV to the Near-IR. Specifically, the PLDR values are of the order of 22, 18 and 4% at 355, 532 and 1064 nm respectively. In an attempt to interpret these results, we apply the hypothesis that smoke particles have near-spherical shapes. Scattering calculations with the T-matrix code support other findings in the literature ([1]- [2]), showing that the near-spherical shape (or closely similar shapes as in [2]), is the only shape that has been shown to reproduce the observed PLDR and Lidar Ratio (LR) values of the stratospheric smoke particles at the three measurement wavelengths.

scholarly journals Wildfire Smoke in the Stratosphere Over Europe–First Measurements of Depolarization and Lidar Ratios at 355, 532, and 1064 nm

2020 ◽  
Vol 237 ◽  
pp. 02036
Author(s):  
Moritz Haarig ◽  
Holger Baars ◽  
Albert Ansmann ◽  
Ronny Engelmann ◽  
Kevin Ohneiser ◽  
...  
Keyword(s):  
Lower Stratosphere ◽  
Wavelength Dependence ◽  
Depolarization Ratio ◽  
Wildfire Smoke ◽  
Lidar Measurements ◽  
Smoke Layer ◽  
Lidar Ratio ◽  
Linear Depolarization Ratio ◽  
532 Nm

Canadian wildfire smoke was detected in the troposphere and lower stratosphere over Europe in August and September 2017. Lidar measurements from various stations of the European Aerosol Research Lidar Network (EARLINET) observed the stratospheric smoke layer. Triple-wavelength (355, 532, and 1064 nm) lidar measurements of the depolarization and the lidar ratio are reported from Leipzig, Germany. The particle linear depolarization ratio of the wildfire smoke in the stratosphere had an exceptional strong wavelength dependence reaching from 0.22 at 355 nm, to 0.18 at 532 nm, and 0.04 at 1064 nm. The lidar ratio increased with wavelength from 40±16 sr at 355 nm, to 66±12 sr at 532 nm, and 92±27 sr at 1064 nm. The development of the stratospheric smoke plume over several months was studied by long-term lidar measurements in Cyprus. The stratospheric smoke layers increased in altitude up to 24 km height.

scholarly journals Multi-wavelength Raman lidar observations of the Eyjafjallajökull volcanic cloud over Potenza, Southern Italy

2011 ◽  
Vol 11 (4) ◽  
pp. 12763-12803 ◽  
Author(s):  
L. Mona ◽  
A. Amodeo ◽  
G. D'Amico ◽  
A. Giunta ◽  
F. Madonna ◽  
...  
Keyword(s):  
Southern Italy ◽  
Saharan Dust ◽  
Depolarization Ratio ◽  
Raman Lidar ◽  
Lidar Measurements ◽  
Ångström Exponent ◽  
Multi Wavelength ◽  
Lidar Ratio ◽  
Linear Depolarization Ratio ◽  
532 Nm

Abstract. Multi-wavelength Raman lidar measurements were performed at CNR-IMAA Atmospheric Observatory (CIAO) during the entire Eyjafjallajökull explosive eruptive period in April–May 2010, whenever weather conditions permitted. A methodology for volcanic layer identification and accurate aerosol typing has been developed on the basis both of the multi-wavelength Raman lidar measurements and EARLINET measurements performed at CIAO since 2000. The aerosol mask for lidar measurements performed at CIAO during the 2010 Eyjafjallajökull eruption has been obtained. Volcanic aerosol layers have been observed in different periods: 19–22 April, 27–29 April, 8–9 May, 13–14 May and 18–19 May. A maximum aerosol optical depth of about 0.12–0.13 was observed on 20 April, 22:00 UTC and 13 May, 20:30 UTC. Volcanic particles have been detected both at low altitudes, in the free troposphere and in the upper troposphere. Intrusions into the PBL have been revealed on 21–22 April and 13 May. In the April–May period Saharan dust intrusions typically occur in Southern Italy. For the period under investigations, a Saharan dust intrusion was observed on 13–14 May: dust and volcanic particles have been simultaneously observed at CIAO both at separated different levels and mixed within the same layer. Lidar ratios at 355 and 532 nm, Ångström exponent at 355/532 nm, backscatter related Ångström exponent at 532/1064 nm and particle linear depolarization ratio at 532 nm measured inside the detected volcanic layers have been discussed. The dependence of these quantities on relative humidity (RH) has been investigated by using co-located microwave profiler measurements. The particle linear depolarization ratio increasing with RH, lidar ratio values at 355 nm around 80 sr, and values of the ratio of lidar ratios greater than 1 suggest the presence of sulfates mixed with continental aerosol. Lower lidar ratio values (around 40 sr) increasing with RH and values of the ratio of lidar ratios lower than 1 indicate the presence of some aged ash inside these sulfate layers.

scholarly journals The potential of elastic and polarization lidars to retrieve extinction profiles

2020 ◽  
Vol 13 (2) ◽  
pp. 893-905 ◽  
Author(s):  
Elina Giannakaki ◽  
Panos Kokkalis ◽  
Eleni Marinou ◽  
Nikolaos S. Bartsotas ◽  
Vassilis Amiridis ◽  
...  
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Dust Particles ◽  
Depolarization Ratio ◽  
Lidar System ◽  
Lidar Measurements ◽  
Lidar Ratio ◽  
Linear Depolarization Ratio ◽  
Aerosol Types ◽  
532 Nm

Abstract. A new method, called ElEx (elastic extinction), is proposed for the estimation of extinction coefficient lidar profiles using only the information provided by the elastic and polarization channels of a lidar system. The method is applicable to lidar measurements both during daytime and nighttime under well-defined aerosol mixtures. ElEx uses the particle backscatter profiles at 532 nm and the vertically resolved particle linear depolarization ratio measurements at the same wavelength. The particle linear depolarization ratio and the lidar ratio values of pure aerosol types are also taken from literature. The total extinction profile is then estimated and compared well with Raman retrievals. In this study, ElEx was applied in an aerosol mixture of marine and dust particles at Finokalia station during the CHARADMExp campaign. Any difference between ElEx and Raman extinction profiles indicates that the nondust component could be probably attributed to polluted marine or polluted continental aerosols. Comparison with sun photometer aerosol optical depth observations is performed as well during daytime. Differences in the total aerosol optical depth are varying between 1.2 % and 72 %, and these differences are attributed to the limited ability of the lidar to correctly represent the aerosol optical properties in the near range due to the overlap problem.

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

2010 ◽  
Vol 3 (3) ◽  
pp. 569-578 ◽  
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.

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

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.

scholarly journals Saharan dust contribution to the Caribbean summertime boundary layer – a lidar study during SALTRACE

2016 ◽  
Vol 16 (18) ◽  
pp. 11535-11546 ◽  
Author(s):  
Silke Groß ◽  
Josef Gasteiger ◽  
Volker Freudenthaler ◽  
Thomas Müller ◽  
Daniel Sauer ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Marine Boundary Layer ◽  
Volume Fraction ◽  
Saharan Dust ◽  
Depolarization Ratio ◽  
Mean Values ◽  
Lidar Ratio ◽  
Linear Depolarization Ratio

Abstract. Dual-wavelength lidar measurements with the small lidar system POLIS of the Ludwig-Maximilians-Universität München were performed during the SALTRACE experiment at Barbados in June and July 2013. Based on high-accuracy measurements of the linear depolarization ratio down to about 200 m above ground level, the dust volume fraction and the dust mass concentration within the convective marine boundary layer can be derived. Additional information from radiosonde launches at the ground-based measurement site provide independent information on the convective marine boundary layer height and the meteorological situation within the convective marine boundary layer. We investigate the lidar-derived optical properties, the lidar ratio and the particle linear depolarization ratio at 355 and 532 nm and find mean values of 0.04 (SD 0.03) and 0.05 (SD 0.04) at 355 and 532 nm, respectively, for the particle linear depolarization ratio, and (26 ± 5) sr for the lidar ratio at 355 and 532 nm. For the concentration of dust in the convective marine boundary layer we find that most values were between 20 and 50 µgm−3. On most days the dust contribution to total aerosol volume was about 30–40 %. Comparing the dust contribution to the column-integrated sun-photometer measurements we see a correlation between high dust contribution, high total aerosol optical depth and a low Angström exponent, and of low dust contribution with low total aerosol optical depth.

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

2018 ◽  
Vol 18 (17) ◽  
pp. 12735-12746 ◽  
Author(s):  
Sung-Kyun Shin ◽  
Matthias Tesche ◽  
Kwanchul Kim ◽  
Maria Kezoudi ◽  
Boyan Tatarov ◽  
...  
Keyword(s):  
Great Basin ◽  
Mineral Dust ◽  
Saharan Dust ◽  
General Behaviour ◽  
Depolarisation Ratio ◽  
Source Regions ◽  
Abstract Knowledge ◽  
Fine Mode ◽  
Lidar Ratio ◽  
Lidar Observations

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.

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

2013 ◽  
Vol 6 (1) ◽  
pp. 911-948 ◽  
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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