scholarly journals Triple-wavelength lidar observations of the linear depolarization ratio of dried marine particles

2018 ◽  
Vol 176 ◽  
pp. 05014
Author(s):  
Moritz Haarig ◽  
Albert Ansmann ◽  
Holger Baars ◽  
Ronny Engelmann ◽  
Dietrich Althausen ◽  
...  
Keyword(s):  
Sea Salt ◽  
Aerosol Layer ◽  
Marine Aerosol ◽  
Depolarization Ratio ◽  
Model Simulations ◽  
Marine Particles ◽  
Linear Depolarization Ratio ◽  
First Time ◽  
Lidar Observations

For aerosol typing with lidar, sea salt particles are usually assumed to be spherical with a consequently low depolarization ratio. Evidence of dried marine particles at the top of the humid marine aerosol layer with a depolarization ratio up to 0.1 has been found at predominately maritime locations on Barbados and in the Southern Atlantic. The depolarization ratio for these probably cubic sea salt particles has been measured at three wavelengths (355, 532 and 1064 nm) simultaneously for the first time and compared to model simulations.

scholarly journals Dry versus wet marine particle optical properties: RH dependence of depolarization ratio, backscatter, and extinction from multiwavelength lidar measurements during SALTRACE

2017 ◽  
Vol 17 (23) ◽  
pp. 14199-14217 ◽  
Author(s):  
Moritz Haarig ◽  
Albert Ansmann ◽  
Josef Gasteiger ◽  
Konrad Kandler ◽  
Dietrich Althausen ◽  
...  
Keyword(s):  
Sea Salt ◽  
Strong Increase ◽  
Aerosol Layer ◽  
Marine Aerosol ◽  
Depolarization Ratio ◽  
Atmospheric Conditions ◽  
Hygroscopic Growth ◽  
Backscatter Coefficient ◽  
Linear Depolarization Ratio ◽  
Lidar Observations

Abstract. Triple-wavelength lidar observations of the depolarization ratio and the backscatter coefficient of marine aerosol as a function of relative humidity (RH) are presented with a 5 min time resolution. The measurements were performed at Barbados (13° N, 59° W) during the Saharan Aerosol Long-range Transport and Aerosol-Cloud interaction Experiment (SALTRACE) winter campaign in February 2014. The phase transition from spherical sea salt particles to cubic-like sea salt crystals was observed with a polarization lidar. The radiosonde and water-vapor Raman lidar observations show a drop in RH below 50 % in the marine aerosol layer simultaneously with a strong increase in particle linear depolarization ratio, which reaches values up to 0.12 ± 0.08 (at 355 nm), 0.15 ± 0.03 (at 532 nm), and 0.10 ± 0.01 (at 1064 nm). The lidar ratio (extinction-to-backscatter ratio) increased from 19 and 23 sr for spherical sea salt particles to 27 and 25 sr (at 355 and 532 nm, respectively) for cubic-like particle ensembles. Furthermore the scattering enhancement due to hygroscopic growth of the marine aerosol particles under atmospheric conditions was measured. Extinction enhancement factors from 40 to 80 % RH of 1.94 ± 0.94 at 355 nm, 3.70 ± 1.14 at 532 nm, and 5.37 ± 1.66 at 1064 nm were found. The enhanced depolarization ratios and lidar ratios were compared to modeling studies of cubic sea salt particles.

scholarly journals Dry versus wet marine particle optical properties: RH dependence of depolarization ratio, backscatter and extinction from multiwavelength lidar measurements during SALTRACE

2017 ◽  
Author(s):  
Moritz Haarig ◽  
Albert Ansmann ◽  
Josef Gasteiger ◽  
Konrad Kandler ◽  
Dietrich Althausen ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Sea Salt ◽  
Strong Increase ◽  
Aerosol Layer ◽  
Marine Aerosol ◽  
Depolarization Ratio ◽  
Atmospheric Conditions ◽  
Backscatter Coefficient ◽  
Lidar Observations ◽  
532 Nm

Abstract. Three-wavelength lidar observations of the depolarization ratio and the backscatter coefficient of marine aerosol as a function of relative humidity (RH) are presented. The humidity dependence of the extinction coefficient and the shape dependence of the lidar ratio were observed in the UV and visible. The phase transition from spherical sea salt particles to cubic-like sea salt crystals was observed under atmospheric conditions with a polarization lidar. The measurements were performed at Barbados (13° N, 59° W) during the SALTRACE winter campaign in February 2014. The radiosonde and Raman lidar observations show a drop in relative humidity below 50 % in the marine aerosol layer simultaneously with a strong increase in particle linear depolarization ratio. Enhanced depolarization ratios (with systematic uncertainty) up to 0.12 ± 0.08 (at 355 nm), 0.15 ± 0.03 (at 532 nm) and 0.10 ± 0.01 (at 1064 nm) were observed and compared to modeling studies of cubic sea salt particles. Lidar-derived correlations of the backscatter coefficient and the depolarization ratio with the relative humidity are reported with a 5-min time resolution. The scattering enhancement due to hygroscopic growth of the marine aerosol particles under atmospheric conditions was determined. Extinction enhancement factors from 40 % to 80 % RH of 2.05 ± 0.82 at 355 nm, 3.73 ± 0.86 at 532 nm and 5.37 ± 1.25 at 1064 nm were found.

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 Aerosol particle depolarization ratio at 1565 nm measured with a Halo Doppler lidar

2020 ◽  
Author(s):  
Ville Vakkari ◽  
Holger Baars ◽  
Stephanie Bohlmann ◽  
Johannes Bühl ◽  
Mika Komppula ◽  
...  
Keyword(s):  
Aerosol Particle ◽  
Birch Pollen ◽  
Stream Line ◽  
Doppler Lidar ◽  
Marine Aerosol ◽  
Depolarization Ratio ◽  
Lidar System ◽  
Multi Wavelength ◽  
Linear Depolarization Ratio ◽  
532 Nm

Abstract. Depolarization ratio is a valuable parameter for lidar-based aerosol categorization. Usually, aerosol particle depolarization ratio is determined at relatively short wavelengths of 355 nm and/or 532 nm, but some multi-wavelength studies including longer wavelengths indicate strong spectral dependency. Here, we investigate the capabilities of Halo Photonics Stream Line Doppler lidars to retrieve the particle linear depolarization ratio at 1565 nm wavelength. We utilize collocated measurements with another lidar system, PollyXT at Limassol, Cyprus, and at Kuopio, Finland, to compare the depolarization ratio observed by the two systems. For mineral dust-dominated cases we find typically a little lower depolarization ratio at 1565 nm than at 355 nm and 532 nm. However, for dust mixed with other aerosol we find higher depolarization ratio at 1565 nm. For polluted marine aerosol we find marginally lower depolarization ratio at 1565 nm compared to 355 nm and 532 nm. For mixed spruce and birch pollen we find a little higher depolarization ratio at 1565 nm compared to 532 nm. Overall, we conclude that Halo Doppler lidars can provide particle linear depolarization ratio at 1565 nm wavelength at least in the lowest 2–3 km above ground.

scholarly journals Aerosol particle depolarization ratio at 1565 nm measured with a Halo Doppler lidar

2021 ◽  
Vol 21 (8) ◽  
pp. 5807-5820
Author(s):  
Ville Vakkari ◽  
Holger Baars ◽  
Stephanie Bohlmann ◽  
Johannes Bühl ◽  
Mika Komppula ◽  
...  
Keyword(s):  
Aerosol Particle ◽  
Mineral Dust ◽  
Birch Pollen ◽  
Doppler Lidar ◽  
Marine Aerosol ◽  
Depolarization Ratio ◽  
Lidar System ◽  
Multi Wavelength ◽  
Linear Depolarization Ratio ◽  
532 Nm

Abstract. The depolarization ratio is a valuable parameter for lidar-based aerosol categorization. Usually, the aerosol particle depolarization ratio is determined at relatively short wavelengths of 355 nm and/or 532 nm, but some multi-wavelength studies including longer wavelengths indicate strong spectral dependency. Here, we investigate the capabilities of Halo Photonics StreamLine Doppler lidars to retrieve the particle linear depolarization ratio at the 1565 nm wavelength. We utilize collocated measurements with another lidar system, PollyXT at Limassol, Cyprus, and at Kuopio, Finland, to compare the depolarization ratio observed by the two systems. For mineral-dust-dominated cases we find typically a slightly lower depolarization ratio at 1565 nm than at 355 and 532 nm. However, for dust mixed with other aerosol we find a higher depolarization ratio at 1565 nm. For polluted marine aerosol we find a marginally lower depolarization ratio at 1565 nm compared to 355 and 532 nm. For mixed spruce and birch pollen we find a slightly higher depolarization ratio at 1565 nm compared to 532 nm. Overall, we conclude that Halo Doppler lidars can provide a particle linear depolarization ratio at the 1565 nm wavelength at least in the lowest 2–3 km above ground.

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 Benefit of depolarization ratio at λ = 1064 nm for the retrieval of the aerosol microphysics from lidar measurements

2014 ◽  
Vol 7 (11) ◽  
pp. 3773-3781 ◽  
Author(s):  
J. Gasteiger ◽  
V. Freudenthaler
Keyword(s):  
Optical Properties ◽  
Mass Concentration ◽  
Volcanic Ash ◽  
Single Scattering ◽  
Depolarization Ratio ◽  
Complex Relation ◽  
Microphysical Properties ◽  
Lidar Measurements ◽  
Increased Sensitivity ◽  
Linear Depolarization Ratio

Abstract. 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%. 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.

scholarly journals Record-breaking ozone loss in the Arctic winter 2010/2011: comparison with 1996/1997

2012 ◽  
Vol 12 (15) ◽  
pp. 7073-7085 ◽  
Author(s):  
J. Kuttippurath ◽  
S. Godin-Beekmann ◽  
F. Lefèvre ◽  
G. Nikulin ◽  
M. L. Santee ◽  
...  
Keyword(s):  
Transport Model ◽  
Chemical Transport ◽  
The Arctic ◽  
Altitude Range ◽  
Chemical Transport Model ◽  
Model Simulations ◽  
Ozone Loss ◽  
Elevated Ozone ◽  
Record Value ◽  
First Time

Abstract. We present a detailed discussion of the chemical and dynamical processes in the Arctic winters 1996/1997 and 2010/2011 with high resolution chemical transport model (CTM) simulations and space-based observations. In the Arctic winter 2010/2011, the lower stratospheric minimum temperatures were below 195 K for a record period of time, from December to mid-April, and a strong and stable vortex was present during that period. Simulations with the Mimosa-Chim CTM show that the chemical ozone loss started in early January and progressed slowly to 1 ppmv (parts per million by volume) by late February. The loss intensified by early March and reached a record maximum of ~2.4 ppmv in the late March–early April period over a broad altitude range of 450–550 K. This coincides with elevated ozone loss rates of 2–4 ppbv sh−1 (parts per billion by volume/sunlit hour) and a contribution of about 30–55% and 30–35% from the ClO-ClO and ClO-BrO cycles, respectively, in late February and March. In addition, a contribution of 30–50% from the HOx cycle is also estimated in April. We also estimate a loss of about 0.7–1.2 ppmv contributed (75%) by the NOx cycle at 550–700 K. The ozone loss estimated in the partial column range of 350–550 K exhibits a record value of ~148 DU (Dobson Unit). This is the largest ozone loss ever estimated in the Arctic and is consistent with the remarkable chlorine activation and strong denitrification (40–50%) during the winter, as the modeled ClO shows ~1.8 ppbv in early January and ~1 ppbv in March at 450–550 K. These model results are in excellent agreement with those found from the Aura Microwave Limb Sounder observations. Our analyses also show that the ozone loss in 2010/2011 is close to that found in some Antarctic winters, for the first time in the observed history. Though the winter 1996/1997 was also very cold in March–April, the temperatures were higher in December–February, and, therefore, chlorine activation was moderate and ozone loss was average with about 1.2 ppmv at 475–550 K or 42 DU at 350–550 K, as diagnosed from the model simulations and measurements.

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