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.

Comparing Halo Doppler lidar depolarization ratio with PollyXT

2020 ◽  
Author(s):  
Ville Vakkari ◽  
Ewan O'Connor ◽  
Holger Baars ◽  
Johannes Bühl
Keyword(s):  
Aerosol Particle ◽  
Mineral Dust ◽  
Chem Phys ◽  
High Spectral Resolution ◽  
Stream Line ◽  
Doppler Lidar ◽  
Depolarization Ratio ◽  
Post Processing ◽  
Wildfire Smoke ◽  
532 Nm

<p>Depolarization ratio is highly valuable in lidar-based aerosol classification and can be used to quantify the contributions of different aerosol types to elevated layers [1]. Typically, aerosol particle depolarization ratio is determined at relatively short wavelengths of 355 nm and/or 532 nm, though some multi-wavelength case studies including 1064 nm have shown strong spectral dependency [2,3]. Here, we demonstrate that Halo Photonics Stream Line Doppler lidars can be used to retrieve aerosol particle depolarization ratio at 1.5 µm wavelength.</p><p> </p><p>We utilize measurements in April-May 2017 at Limassol, Cyprus to compare the Halo 1.5 µm aerosol particle depolarization ratio with Polly XT aerosol particle depolarization ratio. Recently developed post-processing [4] enables retrieving weak signals (as low as -32 dB) with the Halo Doppler lidar. At Limassol, we were able to determine particle depolarization ratio for several cases of mineral dust up to 3 km above ground. Generally, particle depolarization ratio for mineral dust at 1.5 µm appears higher than at shorter wavelengths of 355 nm and 532 nm retrieved by Polly XT. Overall, our results indicate that Halo Doppler lidars can add another wavelength at 1.5 µm to studies on the spectral dependency of aerosol depolarization ratio, at least in the lowest 2-3 km above ground.</p><p> </p><p>[1] Mamouri, R.-E. and Ansmann, A.: Potential of polarization/Raman lidar to separate fine dust, coarse dust, maritime, and anthropogenic aerosol profiles, Atmos. Meas. Tech., 10, 3403-3427, https://doi.org/10.5194/amt-10-3403-2017, 2017.</p><p>[2] Burton, S. P., Hair, J. W., Kahnert, M., Ferrare, R. A., Hostetler, C. A., Cook, A. L., Harper, D. B., Berkoff, T. A., Seaman, S. T., Collins, J. E., Fenn, M. A. and Rogers, R. R.: Observations of the spectral dependence of linear particle depolarization ratio of aerosols using NASA Langley airborne High Spectral Resolution Lidar, Atmos. Chem. Phys., 15, 13453–13473, doi:10.5194/acp-15-13453-2015, 2015.</p><p>[3] Haarig, M., Ansmann, A., Baars, H., Jimenez, C., Veselovskii, I., Engelmann, R. and Althausen, D.: Depolarization and lidar ratios at 355, 532, and 1064 nm and microphysical properties of aged tropospheric and stratospheric Canadian wildfire smoke, Atmos. Chem. Phys., 18, 11847–11861, doi:10.5194/acp-18-11847-2018, 2018.</p><p>[4] Vakkari, V., Manninen, A. J., O’Connor, E. J., Schween, J. H., van Zyl, P. G. and Marinou, E.: A novel post-processing algorithm for Halo Doppler lidars, Atmos. Meas. Tech., 12(2), 839–852, doi:10.5194/amt-12-839-2019, 2019.</p>

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 The characterization of Taklamakan dust properties using a multi-wavelength Raman polarization lidar in Kashi, China

2020 ◽  
Author(s):  
Qiaoyun Hu ◽  
Haofei Wang ◽  
Philippe Goloub ◽  
Zhengqiang Li ◽  
Igor Veselovskii ◽  
...  
Keyword(s):  
Fine Particles ◽  
Depolarization Ratio ◽  
Taklamakan Desert ◽  
Multi Wavelength ◽  
Lidar Ratio ◽  
Linear Depolarization Ratio ◽  
Dust Events ◽  
532 Nm ◽  
Depolarization Ratios

Abstract. The Taklamakan desert is an important dust source for the global atmospheric dust budget and a cause of the dust weather in Eastern Asia. The characterization of the properties and vertical distributions of Taklamakan dust in the source region is still very limited. To fill this gap, the DAO (Dust Aerosol Observation) was conducted in Kashi, China in 2019. Kashi site is about 150 km to the west rim of the Taklamakan desert and is strongly impacted by desert dust aerosols, especially in spring time, i.e. April and May. Apart from dust, fine particles coming from local anthropogenic emissions or/and transported aerosols are also a non-negligible aerosol component. In this study, we provide the first profiling of the 2α + 3β + 3δ lidar profiles of Taklamakan dust based on a multi-wavelength Raman polarization lidar. Four cases, including two Taklamakan dust events (Case 1 and 2) and two polluted dust events (Case 3 and 4) are presented. The lidar ratio in the Taklamakan dust outbreak is found to be 51 ± 8–56 ± 8 sr at 355 nm and 45 ± 7 sr at 532 nm. The particle linear depolarization ratios are about 0.28 ± 0.04–0.32 ± 0.05 at 355 nm, 0.35 ± 0.05 at 532 nm and 0.31 ± 0.05 at 1064 nm. The observed polluted dust is commonly featured with reduced particle linear depolarization ratio and enhanced extinction and backscatter Angstrom exponent. In Case 3, the lidar ratio of polluted dust is about 42 ± 6 sr at 355 nm and 40 ± 6 sr at 532 nm. The particles linear depolarization ratios decrease to about 0.25, with a weak spectral dependence. In Case 4, the variability of lidar ratio and particle linear depolarization ratio is higher than in Case 3, which reflects the complexity of the nature of mixed pollutant and the mixing state. The results provide the first reference for the characteristics of Taklamakan dust measured by Raman lidar. The data could contribute to complementing the dust model and improving the accuracy of climate modeling.

scholarly journals Detection and characterization of birch pollen in the atmosphere using multi-wavelength Raman lidar in Finland

2019 ◽  
Author(s):  
Stephanie Bohlmann ◽  
Xiaoxia Shang ◽  
Elina Giannakaki ◽  
Maria Filioglou ◽  
Annika Saarto ◽  
...  
Keyword(s):  
Birch Pollen ◽  
Pollen Grains ◽  
Mean Value ◽  
Forest Site ◽  
Depolarization Ratio ◽  
Atmospheric Conditions ◽  
Raman Lidar ◽  
Pollen Types ◽  
Multi Wavelength ◽  
532 Nm

Abstract. We present the results of birch pollen characterization using lidar measurements based on a 11-day period of birch pollination from 5 to 15 May 2016 at the European Aerosol Research Lidar Network (EARLINET) station in Vehmasmäki (Kuopio, 62°44′ N, 27°33′ E), Finland. The ground-based multi-wavelength Raman lidar PollyXT performed continuous measurements at this rural forest site and has been combined with a Hirst-type volumetric air sampler which measured the pollen type and concentration on roof level (4 m). The period was separated into two parts due to different atmospheric conditions and detected pollen types. During the first period, high concentrations of birch pollen were measured with a maximum two-hour average pollen concentration of 3700 grains/m³. Other pollen types represented less than 3 % of the total pollen count. In observed pollen layers, the mean particle depolarization ratio at 532 nm was 10 ± 6 % during the intense birch pollination period. Mean lidar ratios were found to be 45 ± 7 and 55 ± 16 sr at 355 and 532 nm, respectively. During the second period, birch pollen was still dominant but a significant contribution of spruce pollen was observed. Spruce pollen grains are highly non-spherical, leading to a larger mean depolarization ratio of 26 ± 7 % of the birch-spruce pollen mixture. Furthermore, higher lidar ratios were observed during this period with a mean value of 60 ± 3 and 62 ± 10 sr at 355 and 532 nm, respectively. The presented study shows the potential of the particle depolarization ratio to track pollen grains in the atmosphere.

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 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 Observation of Long-Range Dust Transport from Mesopotamia and Arabian Peninsula Toward Tehran, Iran

2019 ◽  
Vol 99 ◽  
pp. 02006 ◽  
Author(s):  
Hossein Panahifar ◽  
Hamid Reza Khalesifard
Keyword(s):  
Optical Properties ◽  
Particulate Matter ◽  
Arabian Peninsula ◽  
Urban Pollution ◽  
Depolarization Ratio ◽  
Dust Transport ◽  
Linear Depolarization Ratio ◽  
Dust Events ◽  
Aerosol Types ◽  
532 Nm

Continuous vertically resolved aerosol measurements using lidar were performed in Tehran, Iran. Lidar results has been used in combination with particulate matter monitoring, synoptic meteorology observa- tion as well as satellite-based measurements. The aerosol types are classified by their optical properties. The volume linear depolarization ratio (VLDR) at 532 nm lies mostly between 0:05-0:10. These results show that mostly urban pollution mixed with particles are present in the atmosphere above Tehran. During dust events, the VLDR at 532 nm lies between 0:20-0:35.

Design and performance simulation of 532 nm Rayleigh–Mie Doppler lidar system for 5–50 km wind measurement

2018 ◽  
Vol 412 ◽  
pp. 7-13
Author(s):  
Fahua Shen ◽  
Bangxin Wang ◽  
Wenjuan Shi ◽  
Peng Zhuang ◽  
Chengyun Zhu ◽  
...  
Keyword(s):  
Doppler Lidar ◽  
Lidar System ◽  
Performance Simulation ◽  
Wind Measurement ◽  
And Performance ◽  
532 Nm

scholarly journals Optical and geometrical aerosol particle properties over the United Arab Emirates

2020 ◽  
Vol 20 (14) ◽  
pp. 8909-8922 ◽  
Author(s):  
Maria Filioglou ◽  
Elina Giannakaki ◽  
John Backman ◽  
Jutta Kesti ◽  
Anne Hirsikko ◽  
...  
Keyword(s):  
Aerosol Particle ◽  
United Arab Emirates ◽  
Mineral Dust ◽  
Depolarization Ratio ◽  
Raman Lidar ◽  
Particle Properties ◽  
Measurement Site ◽  
Ångström Exponent ◽  
Lidar Ratio ◽  
532 Nm

Abstract. One year of ground-based night-time Raman lidar observations has been analysed under the Optimization of Aerosol Seeding In rain enhancement Strategies (OASIS) project, in order to characterize the aerosol particle properties over a rural site in the United Arab Emirates. In total, 1130 aerosol particle layers were detected during the 1-year measurement campaign which took place between March 2018 and February 2019. Several subsequent aerosol layers could be observed simultaneously in the atmosphere up to 11 km. The observations indicate that the measurement site is a receptor of frequent dust events, but predominantly the dust is mixed with aerosols of anthropogenic and/or marine origin. The mean aerosol optical depth over the measurement site ranged at 0.37 ± 0.12 and 0.21 ± 0.11 for 355 and 532 nm, respectively. Moreover, mean lidar ratios of 43 ± 11 sr at a wavelength of 355 nm and 39 ± 10 sr at 532 nm were found. The average linear particle depolarization ratio measured over the course of the campaign was 15 ± 6 % and 19 ± 7 % at the 355 and 532 nm wavelengths, respectively. Since the region is both a source and a receptor of mineral dust, we have also explored the properties of Arabian mineral dust of the greater area of the United Arab of Emirates and the Arabian Peninsula. The observed Arabian dust particle properties were 45 ± 5 (42 ± 5) sr at 355 (532) nm for the lidar ratio, 25 ± 2 % (31 ± 2 %) for the linear particle depolarization ratio at 355 (532) nm, and 0.3 ± 0.2 (0.2 ± 0.2) for the extinction-related Ångström exponent (backscatter-related Ångström exponent) between 355 and 532 nm. This study is the first to report comprehensive optical properties of the Arabian dust particles based on 1-year long observations, using to their fullest the capabilities of a multi-wavelength Raman lidar instrument. The results suggest that the mineral dust properties over the Middle East and western Asia, including the observation site, are comparable to those of African mineral dust with regard to the particle depolarization ratios, but not for lidar ratios. The smaller lidar ratio values in this study compared to the reference studies are attributed to the difference in the geochemical characteristics of the soil originating in the study region compared to northern Africa.

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