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 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 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 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.

STUDIES OF THE IMPACT OF AEROSOL OPTICAL PROPERTIES ON CLIMATE CHANGE PROCESSES

2011 ◽  
Vol 10 (1) ◽  
pp. 155-159
Author(s):  
Tymon Zielinski ◽  
Przemyslaw Makuch ◽  
Agata Strzalkowska ◽  
Agnieszka Ponczkowska ◽  
Tomasz Petelski ◽  
...  
Keyword(s):  
Climate Change ◽  
Optical Properties ◽  
Change Processes ◽  
Aerosol Optical Properties ◽  
The Impact

scholarly journals Observations of aerosol optical properties at a coastal site in Hong Kong, South China

2017 ◽  
Vol 17 (4) ◽  
pp. 2653-2671 ◽  
Author(s):  
Jiaping Wang ◽  
Aki Virkkula ◽  
Yuan Gao ◽  
Shuncheng Lee ◽  
Yicheng Shen ◽  
...  
Keyword(s):  
Optical Properties ◽  
Hong Kong ◽  
Light Scattering ◽  
South China ◽  
Eastern China ◽  
Light Extinction ◽  
Aerosol Optical Properties ◽  
Air Masses ◽  
Rural Sites ◽  
The Impact

Abstract. Temporal variations in aerosol optical properties were investigated at a coastal station in Hong Kong based on the field observation from February 2012 to February 2015. At 550 nm, the average light-scattering (151 ± 100 Mm−1) and absorption coefficients (8.3 ± 6.1 Mm−1) were lower than most of other rural sites in eastern China, while the single-scattering albedo (SSA  =  0.93 ± 0.05) was relatively higher compared with other rural sites in the Pearl River Delta (PRD) region. Correlation analysis confirmed that the darkest aerosols were smaller in particle size and showed strong scattering wavelength dependencies, indicating possible sources from fresh emissions close to the measurement site. Particles with Dp of 200–800 nm were less in number, yet contributed the most to the light-scattering coefficients among submicron particles. In summer, both ΔBC / ΔCO and SO2 / BC peaked, indicating the impact of nearby combustion sources on this site. Multi-year backward Lagrangian particle dispersion modeling (LPDM) and potential source contribution (PSC) analysis revealed that these particles were mainly from the air masses that moved southward over Shenzhen and urban Hong Kong and the polluted marine air containing ship exhausts. These fresh emission sources led to low SSA during summer months. For winter and autumn months, contrarily, ΔBC / ΔCO and SO2 / BC were relatively low, showing that the site was more under influence of well-mixed air masses from long-range transport including from South China, East China coastal regions, and aged aerosol transported over the Pacific Ocean and Taiwan, causing stronger abilities of light extinction and larger variability of aerosol optical properties. Our results showed that ship emissions in the vicinity of Hong Kong could have visible impact on the light-scattering and absorption abilities as well as SSA at Hok Tsui.

scholarly journals Aerosol effects modeling using an online coupling between the meteorological model WRF and the chemistry-transport model CHIMERE

2016 ◽  
Author(s):  
Régis Briant ◽  
Paolo Tuccella ◽  
Adrien Deroubaix ◽  
Dmitry Khvorostyanov ◽  
Laurent Menut ◽  
...  
Keyword(s):  
Optical Properties ◽  
Transport Model ◽  
Regional Scale ◽  
Total Duration ◽  
Radiation Budget ◽  
Aerosol Optical Properties ◽  
Chemistry Transport Model ◽  
Meteorological Model ◽  
Western Asia ◽  
The Impact

Abstract. The presence of airborne aerosols affects the meteorology as it induces a perturbation in the radiation budget, the number of cloud condensation nuclei and the cloud micro-physics. Those effects are difficult to model at regional scale as several distinct models are usually involved. In this paper, the coupling of the CHIMERE chemistry-transport model with the WRF meteorological model using the OASIS3-MCT coupler is presented. WRF meteorological fields along with CHIMERE aerosol optical properties are exchanged through the coupler at a high frequency in order to model the aerosol direct and semidirect effects. The WRF-CHIMERE online model has a higher computational burden than both models ran separately in offline mode (up to 42 % higher). This is mainly due to some additional computations made within the models such as more frequent calls to meteorology treatment routines or calls to optical properties computations routines. On the other hand, the overall time required to perform the OASIS3-MCT exchanges is not significant compared to the total duration of the simulations. The impact of the coupling is evaluated on a case study over Europe, northern Africa, Middle East and western Asia during the Summer 2012, through comparisons of the offline and two online simulations (with and without the aerosol optical properties feedback) to observations of temperature, Aerosol Optical Depth (AOD) and surface PM10 (particulate matter with diameters lower than 10 µm) concentrations. Result shows that using the optical properties feedback induces a radiative forcing (average forcing of −4.8 W.m−2) which creates a perturbation in the average surface temperatures over desert areas (up to 2.6° locally) along with an increase of both AOD and PM10 concentrations.

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