scholarly journals Studies on Aerosol Optical Properties at High Altitude Station in Western Himalayas Using Raman Lidar

2020 ◽  
Vol 237 ◽  
pp. 02034
Author(s):  
Shishir Kumar Singh ◽  
Jaswant ◽  
S.R. Radhakrishnan ◽  
Davender Sethi ◽  
Chhemendra Sharma
Keyword(s):  
Optical Properties ◽  
Extinction Coefficient ◽  
Spherical Particles ◽  
Western Himalayas ◽  
Depolarization Ratio ◽  
Raman Lidar ◽  
Inversion Algorithm ◽  
Backscatter Coefficient ◽  
Aerosol Optical Properties ◽  
Linear Depolarization Ratio

The aerosol optical properties have been investigated using the Raman lidar system for the month of November 2018 at the western Himalayan station of Palampur. Before deriving the optical properties, the lidar data has been applied with initial pre-processing such as Dead time correction, atmospheric noise correction, temporal and spatial averaging, range correction, gluing etc. The optical properties such as backscatter coefficient, extinction coefficient and linear depolarization ratio have been derived by using the inversion algorithm proposed by Fernald. The results show that the backscatter coefficient was found in the range from 9.00E-9 m−1sr−1 to 4.97E-6 m−1sr−1 and the extinction coefficient was found in the range from 3.16E-7m-1 to 1.74E-4m-1. The Linear depolarization ratio was in the range from 0.0179 to 0.621 with lower values at near heights suggesting the dominance of spherical particles at the lower heights. We have also observed a cloud layer at a height of 9.5 km to 12.1 km with high depolarization ratio during the observation period on 22/11/2018.

scholarly journals Experimental assessment of a micro-pulse lidar system in comparison with reference lidar measurements for aerosol optical properties retrieval

2021 ◽  
Vol 14 (7) ◽  
pp. 5225-5239
Author(s):  
Carmen Córdoba-Jabonero ◽  
Albert Ansmann ◽  
Cristofer Jiménez ◽  
Holger Baars ◽  
María-Ángeles López-Cayuela ◽  
...  
Keyword(s):  
Optical Properties ◽  
Depolarization Ratio ◽  
Backscatter Coefficient ◽  
Aerosol Optical Properties ◽  
Experimental Assessment ◽  
Total Particle ◽  
Linear Depolarization Ratio ◽  
Field Intercomparison ◽  
Micro Pulse Lidar ◽  
The Impact

Abstract. Simultaneous observations of a polarized micro-pulse lidar (P-MPL) system and two reference European Aerosol Research Lidar Network lidars running at the Leipzig site Germany, 51.4∘ N, 12.4∘ E; 125 m a.s.l.) were performed during a comprehensive 2-month field intercomparison campaign in summer 2019. An experimental assessment regarding both the overlap (OVP) correction of the P-MPL signal profiles and the volume linear depolarization ratio (VLDR) analysis, together with its impact on the retrieval of the aerosol optical properties, is achieved; the experimental procedure used is also described. The optimal lidar-specific OVP function is experimentally determined, highlighting that the one delivered by the P-MPL manufacturer cannot be used long. Among the OVP functions examined, the averaged function between those obtained from the comparison of the P-MPL observations with those of the other two reference lidars seems to be the best proxy at both near- and far-field ranges. In addition, the impact of the OVP function on the accuracy of the retrieved profiles of the total particle backscatter coefficient (PBC) and the particle linear depolarization ratio (PLDR) is examined. The VLDR profile is obtained and compared with that derived from the reference lidar, showing that it needs to be corrected by a small offset value with good accuracy. Once P-MPL measurements are optimally (OVP, VLDR) corrected, both the PBC and PLDR profiles can be accurately derived and are in good agreement with reference aerosol retrievals. Overall, as a systematic requirement for lidar systems, an adequate OVP function determination and VLDR testing analysis needs to be performed on a regular basis to correct the P-MPL measurements in order to derive suitable aerosol products. A dust event observed in Leipzig in June 2019 is used for illustration.

scholarly journals Experimental calibration assessment of a MPLNET/Micro-Pulse Lidar system in comparison with EARLINET lidar measurements for aerosol optical properties retrieval

2020 ◽  
Author(s):  
Carmen Córdoba-Jabonero ◽  
Albert Ansmann ◽  
Cristofer Jiménez ◽  
Holger Baars ◽  
María-Ángeles López-Cayuela ◽  
...  
Keyword(s):  
Optical Properties ◽  
Depolarization Ratio ◽  
Backscatter Coefficient ◽  
Experimental Calibration ◽  
Experimental Procedure ◽  
Lidar Measurements ◽  
Total Particle ◽  
Linear Depolarization Ratio ◽  
Micro Pulse Lidar ◽  
The Impact

Abstract. Simultaneous observations of a polarized Micro-Pulse Lidar (P-MPL) system, currently operative within MPLNET (NASA Micro-Pulse Lidar Network), with two referenced EARLINET (European Aerosol Research Lidar Network) lidars, running at Leipzig site (Germany, 51.4º N 12.4º E, 125 m a.s.l.), were performed during a comprehensive two-month field campaign in summer 2019. A calibration assessment regarding the overlap (OVP) correction of the P-MPL signal profiles and its impact in the retrieval of the optical properties is achieved, describing also the experimental procedure used. The optimal lidar-specific OVP function for correcting the P-MPL measurements is experimentally determined, highlighting that the OVP function as delivered by the P-MPL manufacturer cannot be used. Among the OVP functions examined, the averaged one between those obtained from the comparison of the P-MPL observations with those of the other two referenced lidars seems to be the best proxy at both near- and far-field ranges. In addition, the impact of the OVP function in the accuracy of the retrieved profiles of the total particle backscatter coefficient (PBC) and the particle linear depolarization ratio (PLDR) is examined. First, the volume linear depolarization ratio (VLDR) profile is obtained and compared to the reference lidars, showing it needs to be corrected by a small offset value within a good accuracy. Once P-MPL measurements are optimally OVP-corrected, the PBC profiles (and hence the PLDR ones) can be derived using the Klett-Fernald approach. In addition, an alternative method based on the separation of the total PBC into their aerosol components is presented in order to estimate the total particle extinction coefficient (PEC) profile, and hence the Aerosol Optical Depth, from elastic P-MPL measurements. A dust event as observed at Leipzig in June 2019 is used for illustration. In overall, an adequate OVP function is needed to be determined in a regular basis to calibrate the P-MPL system in order to derive suitable aerosol products.

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 Airborne measurements of aerosol optical properties related to early spring transport of mid-latitude sources into the Arctic

2010 ◽  
Vol 10 (11) ◽  
pp. 5011-5030 ◽  
Author(s):  
R. A. de Villiers ◽  
G. Ancellet ◽  
J. Pelon ◽  
B. Quennehen ◽  
A. Schwarzenboeck ◽  
...  
Keyword(s):  
Optical Properties ◽  
The Arctic ◽  
Depolarization Ratio ◽  
Aerosol Optical Properties ◽  
Accumulation Mode ◽  
Color Ratio ◽  
Aerosol Sources ◽  
Aerosol Backscatter ◽  
532 Nm

Abstract. Airborne lidar and in-situ measurements of the aerosol properties were conducted between Svalbard Island and Scandinavia in April 2008. Evidence of aerosol transport from Europe and Asia is given. The analysis of the aerosol optical properties based on a multiwavelength lidar (355, 532, 1064 nm) including volume depolarization at 355 nm aims at distinguishing the role of the different aerosol sources (Siberian wild fires, Eastern Asia and European anthropogenic emissions). Combining, first aircraft measurements, second FLEXPART simulations with a calculation of the PBL air fraction originating from the three different mid-latitude source regions, and third level-2 CALIPSO data products (i.e. backscatter coefficient 532 nm,volume depolarization and color ratio between 1064 and 532 nm in aerosol layers) along the transport pathways, appears a valuable approach to identify the role of the different aerosol sources even after a transport time larger than 4 days. Optical depth of the aerosol layers are always rather small (<4%) while transported over the Arctic and ratio of the total attenuated backscatter (i.e. including molecular contribution) provide more stable result than conventional aerosol backscatter ratio. Above Asia, CALIPSO data indicate more depolarization (up to 15%) and largest color ratio (>0.5) for the northeastern Asia emissions (i.e. an expected mixture of Asian pollution and dust), while low depolarization together with smaller and quasi constant color ratio (≈0.3) are observed for the Siberian biomass burning emissions. A similar difference is visible between two layers observed by the aircraft above Scandinavia. The analysis of the time evolution of the aerosol optical properties revealed by CALIPSO between Asia and Scandinavia shows a gradual decrease of the aerosol backscatter, depolarization ratio and color ratio which suggests the removal of the largest particles in the accumulation mode. A similar study conducted for a European plume has shown aerosol optical properties intermediate between the two Asian sources with color ratio never exceeding 0.4 and moderate depolarization ratio being always less than 8%, i.e. less aerosol from the accumulation mode.

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

2014 ◽  
Vol 7 (5) ◽  
pp. 5095-5115
Author(s):  
J. Gasteiger ◽  
V. Freudenthaler
Keyword(s):  
Optical Properties ◽  
Mass Concentration ◽  
Single Scattering ◽  
Sufficient Information ◽  
Depolarization Ratio ◽  
Aerosol Composition ◽  
Microphysical Properties ◽  
Lidar Measurements ◽  
Increased Sensitivity ◽  
Linear Depolarization Ratio

Abstract. A better quantification of aerosol microphysical and optical properties is required to improve the modelling of aerosol effects on weather and climate. This task is methodologically demanding due to the huge diversity of aerosol composition and of their shape and size distribution, and due to the complexity of the relation between the microphysical and optical properties. Lidar remote sensing is a valuable tool to gain spatially and temporally resolved information on aerosol properties. Advanced lidar systems provide sufficient information on the aerosol optical properties for the retrieval of important aerosol microphysical properties. Recently, the mass concentration of transported volcanic ash, which is relevant for the flight safety of airplanes, 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 the setup of MULIS and POLIS of the LMU in Munich which measure the linear depolarization ratio at 355 nm and 532 nm with high accuracy. By comparing results of retrievals applied to simulated lidar measurements with and without the depolarization at 1064 nm it is found that the availability of 1064 nm depolarization measurements reduces the uncertainty of the retrieved mass concentration and effective particle size by a factor of about 2–3. This significant improvement in accuracy is the result of the increased sensitivity of the lidar setup to larger particles. However, the retrieval of the single scattering albedo, which is relevant for the radiative transfer in aerosol layers, does hardly benefit from the availability of 1064 nm depolarization measurements.

scholarly journals Rehearsal for Assessment of atmospheric optical Properties during biomass burning Events and Long-range transportation episodes at Metropolitan Area of São Paulo-Brazil (RAPEL)

2018 ◽  
Vol 176 ◽  
pp. 08011 ◽  
Author(s):  
Fábio J. S. Lopes ◽  
Juan Luis Guerrero-Rascado ◽  
Jose A. Benavent-Oltra ◽  
Roberto Román ◽  
Gregori A. Moreira ◽  
...  
Keyword(s):  
Optical Properties ◽  
Long Range ◽  
Metropolitan Area ◽  
Sao Paulo ◽  
Vertical Profiles ◽  
São Paulo ◽  
Inversion Algorithm ◽  
Aerosol Transport ◽  
Aerosol Optical Properties ◽  
Aerosol Properties

During the period of August-September 2016 an intensive campaign was carried out to assess aerosol properties in São Paulo-Brazil aiming to detect long-range aerosol transport events and to characterize the instrument regarding data quality. Aerosol optical properties retrieved by the GALION - LALINET SPU lidar station and collocated AERONET sunphotometer system are presented as extinction/ backscatter vertical profiles with microphysical products retrieved with GRASP inversion algorithm.

scholarly journals Synchronous polar winter starphotometry and lidar measurements at a High Arctic station

2015 ◽  
Vol 8 (9) ◽  
pp. 3789-3809 ◽  
Author(s):  
K. Baibakov ◽  
N. T. O'Neill ◽  
L. Ivanescu ◽  
T. J. Duck ◽  
C. Perro ◽  
...  
Keyword(s):  
Optical Properties ◽  
Aerosol Optical Depth ◽  
Research Laboratory ◽  
Recent Progress ◽  
High Arctic ◽  
Raman Lidar ◽  
Backscatter Coefficient ◽  
Atmospheric Research ◽  
Lidar Measurements ◽  
Fine Mode

Abstract. We present recent progress on nighttime retrievals of aerosol and cloud optical properties over the PEARL (Polar Environmental Atmospheric Research Laboratory) station at Eureka (Nunavut, Canada) in the High Arctic (80° N, 86° W). In the spring of 2011 and 2012, a star photometer was employed to acquire aerosol optical depth (AOD) data, while vertical aerosol and cloud backscatter profiles were measured using the CANDAC Raman Lidar (CRL). We used a simple backscatter coefficient threshold (βthr) to distinguish aerosols from clouds and, assuming that aerosols were largely fine mode (FM)/sub-micron, to distinguish FM aerosols from coarse mode (CM)/super-micron cloud or crystal particles. Using prescribed lidar ratios, we computed FM and CM AODs that were compared with analogous AODs estimated from spectral star photometry. We found (βthr dependent) coherences between the lidar and star photometer for both FM events and CM cloud and crystal events with averaged, FM absolute differences being

scholarly journals Helicopter-borne observations of the continental background aerosol in combination with remote sensing and ground-based measurements

2017 ◽  
Author(s):  
Sebastian Düsing ◽  
Birgit Wehner ◽  
Patric Seifert ◽  
Albert Ansmann ◽  
Holger Baars ◽  
...  
Keyword(s):  
Optical Properties ◽  
Aerosol Particle ◽  
Extinction Coefficient ◽  
Cloud Condensation Nuclei ◽  
In Situ Measurements ◽  
Light Extinction ◽  
Backscatter Coefficient ◽  
Light Extinction Coefficient ◽  
Lidar Measurements

Abstract. This study presents vertical profiles up to a height of 2300 m a.s.l. of aerosol microphysical and optical properties and cloud condensation nuclei (CCN). Corresponding data have been measured during a field campaign as part of the High-Definition Clouds and Precipitation for Advancing Climate Prediction (HD(CP)2) Observational Prototype Experiments (HOPE), which took place at Melpitz, Germany from September 9 to 29, 2013. The helicopter-borne payload ACTOS (Airborne Cloud and Turbulence Observation System) was used to determine the aerosol particle number size distribution (PNSD), the number concentrations of aerosol particles (PNC) and cloud condensation nuclei (CCN) (CCN-NC), the ambient relative humidity (RH), and temperature (T). Simultaneous measurements on ground provided a holistic view on aerosol microphysical properties such as the PNSD, the chemical composition and the CCN-NC. Additional measurements of a 3 + 2 wavelength polarization lidar system (PollyXT) provided profiles of the aerosol particle light backscatter coefficient (σbsc) for three wavelengths (355, 532 and 1064 nm). From profiles of σbsc profiles of the aerosol particle light extinction coefficient (σext) were determined using the extinction-to-backscatter ratio. Furthermore, CCN-NC profiles were estimated on basis of the lidar-measurements. Ambient state optical properties of aerosol particles were derived on the basis of airborne in situ measurements of ACTOS (PNSD) and in situ measurements on ground (chemical aerosol characterization) using Mie-theory. On the basis of ground-based and airborne measurements, this work investigates the representativeness of ground-based aerosol microphysical properties for the boundary layer for two case-studies. The PNSD measurements on ground showed a good agreement with the measurements provided with ACTOS for lower altitudes. The ground-based measurements of PNC and CCN-NC are representative for the PBL when the PBL is well mixed. Locally isolated new particle formation events on ground or at the top of the PBL led to vertical variability in the here presented cases and ground-based measurements are not representative for the PBL. Furthermore, the lidar-based estimates of CCN-NC profiles were compared with the airborne in situ measurements of ACTOS. This comparison showed good agreements within the uncertainty range. Finally, this work provides a closure study between the optical aerosol particle properties in ambient state based on the airborne ACTOS measurements and derived with the lidar measurements. The investigation of the optical properties shows for 14 measurement-points that the airborne-based particle light backscatter coefficient is for 1064 nm 50 % smaller than the measurements of the lidar system, 27.6 % smaller for 532 nm and 29.9 % smaller for 355 nm. These results are quite promising, since in-situ measurement based Mie-calculations of the particle light backscattering are scarce and the modelling is quite challenging. In contradiction for the particle light extinction coefficient retrieved from the airborne in situ measurements were found a good agreement. The airborne-based particle light extinction coefficient was just 7.9 % larger for 532 nm and 3.5 % smaller for 355 nm, for an assumed lidar ratio (LR) of 55 sr. The particle light extinction coefficient for 1064 nm was derived with a LR of 30 sr. For this wavelength, the airborne-based particle light extinction coefficient is 5.2 % smaller than the lidar-measurements. Also, the correlation for the particle light extinction coefficient in combination with Mie-based LR's are in agreement for typical LR's of European background aerosol.

scholarly journals Joint elastic side-scattering LIDAR and Raman LIDAR measurements of aerosol optical properties in south east Colorado

2017 ◽  
Vol 12 (03) ◽  
pp. P03008-P03008 ◽  
Author(s):  
L. Wiencke ◽  
V. Rizi ◽  
M. Will ◽  
C. Allen ◽  
A. Botts ◽  
...  
Keyword(s):  
Optical Properties ◽  
Raman Lidar ◽  
Aerosol Optical Properties ◽  
Lidar Measurements

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.

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