scholarly journals Optical, microphysical, mass and geometrical properties of aged volcanic particles observed over Athens, Greece, during the Eyjafjallajökull eruption in April 2010 through synergy of Raman lidar and sunphotometer measurements

2013 ◽  
Vol 13 (18) ◽  
pp. 9303-9320 ◽  
Author(s):  
P. Kokkalis ◽  
A. Papayannis ◽  
V. Amiridis ◽  
R. E. Mamouri ◽  
I. Veselovskii ◽  
...  
Keyword(s):  
Refractive Index ◽  
Vertical Distribution ◽  
Mass Concentration ◽  
Effective Radius ◽  
Raman Lidar ◽  
Optical Extinction ◽  
Geometrical Properties ◽  
Lidar Measurements ◽  
Aerosol Types ◽  
532 Nm

Abstract. Vertical profiles of the optical (extinction and backscatter coefficients, lidar ratio and Ångström exponent), microphysical (mean effective radius, mean refractive index, mean number concentration) and geometrical properties as well as the mass concentration of volcanic particles from the Eyjafjallajökull eruption were retrieved at selected heights over Athens, Greece, using multi-wavelength Raman lidar measurements performed during the period 21–24 April 2010. Aerosol Robotic Network (AERONET) particulate columnar measurements along with inversion schemes were initialized together with lidar observations to deliver the aforementioned products. The well-known FLEXPART (FLEXible PARTicle dispersion model) model used for volcanic dispersion simulations is initiated as well in order to estimate the horizontal and vertical distribution of volcanic particles. Compared with the lidar measurements within the planetary boundary layer over Athens, FLEXPART proved to be a useful tool for determining the state of mixing of ash with other, locally emitted aerosol types. The major findings presented in our work concern the identification of volcanic particles layers in the form of filaments after 7-day transport from the volcanic source (approximately 4000 km away from our site) from the surface and up to 10 km according to the lidar measurements. Mean hourly averaged lidar signals indicated that the layer thickness of volcanic particles ranged between 1.5 and 2.2 km. The corresponding aerosol optical depth was found to vary from 0.01 to 0.18 at 355 nm and from 0.02 up to 0.17 at 532 nm. Furthermore, the corresponding lidar ratios (S) ranged between 60 and 80 sr at 355 nm and 44 and 88 sr at 532 nm. The mean effective radius of the volcanic particles estimated by applying inversion scheme to the lidar data found to vary within the range 0.13–0.38 μm and the refractive index ranged from 1.39+0.009i to 1.48+0.006i. This high variability is most probably attributed to the mixing of aged volcanic particles with other aerosol types of local origin. Finally, the LIRIC (LIdar/Radiometer Inversion Code) lidar/sunphotometric combined inversion algorithm has been applied in order to retrieve particle concentrations. These have been compared with FLEXPART simulations of the vertical distribution of ash showing good agreement concerning not only the geometrical properties of the volcanic particles layers but also the particles mass concentration.

scholarly journals Optical, microphysical, mass and geometrical properties of aged volcanic particles observed over Athens, Greece, during the Eyjafjallajökull eruption in April 2010 through synergy of Raman lidar and sunphotometer measurements

2013 ◽  
Vol 13 (2) ◽  
pp. 5315-5364
Author(s):  
P. Kokkalis ◽  
A. Papayannis ◽  
V. Amiridis ◽  
R. E. Mamouri ◽  
I. Veselovskii ◽  
...  
Keyword(s):  
Refractive Index ◽  
Mass Concentration ◽  
Effective Radius ◽  
Data Sets ◽  
Raman Lidar ◽  
Optical Extinction ◽  
Geometrical Properties ◽  
Multi Wavelength ◽  
Using Data ◽  
532 Nm

Abstract. Vertical profiles of the optical (extinction and backscatter coefficients, lidar ratio and Ångström exponent), microphysical (mean effective radius, mean refractive index, mean number concentration) and geometrical properties, as well as of the mass concentration of volcanic particles from the Eyjafjallajökull eruption were retrieved at selected heights over Athens, Greece using a multi-wavelength Raman lidar system and inversion models, during 21–24 April 2010. Additionally, Aerosol Robotic Network (AERONET) particulate columnar measurements indicated the presence of volcanic particles over our area. Simulations of the volcanic partilcles dispersion, done by the FLEXPART model, confirmed the presence of these particles over Athens. Our lidar data showed volcanic particles layers, in the form of filaments after 7-day transport from the source (approximately 4000 km away from our site) between from ground levels up to nearly 10 km. Over Athens the volcanic particles layers were found to be mixed with locally produced aerosols, inside the Planetary Boundary Layer (PBL). Mean hourly-averaged lidar signals indicated that the layer thickness of volcanic particles, ranged between 1.5 and 2.2 km. The corresponding aerosol optical depth (AOD) found to vary from 0.014 to 0.184 at 355 nm and from 0.017 up to 0.174 at 532 nm. Furthermore, the corresponding lidar ratios (LR) ranged between 59.7–79.6 sr (at 355 nm) and 43.9–88.3 sr (at 532 nm). Additionally, we calculated that the mean effective radius of the volcanic particles was 0.13–0.38 μm, while their refractive index ranged from 1.39+0.009i to 1.48+0.006i. Finally, our data also allowed us to quantitatively compare, for the first time, the volcanic ash concentrations simulated by FLEXPART with those calculated by the inversion code LIRIC, using data sets derived from coincident lidar-AERONET measurements. In general, good agreement was found between simulations and observations, concerning not only the geometrical properties of the volcanic particles layers, but also the particles mass concentration, with a correlation coefficient of the order of 0.75.

scholarly journals EARLINET dust observations vs. BSC-DREAM8b modeled profiles: 12-year-long systematic comparison at Potenza, Italy

2014 ◽  
Vol 14 (16) ◽  
pp. 8781-8793 ◽  
Author(s):  
L. Mona ◽  
N. Papagiannopoulos ◽  
S. Basart ◽  
J. Baldasano ◽  
I. Binietoglou ◽  
...  
Keyword(s):  
Center Of Mass ◽  
Saharan Dust ◽  
Raman Lidar ◽  
Dust Layer ◽  
Systematic Comparison ◽  
Dust Extinction ◽  
Lidar Measurements ◽  
Order Of Magnitude ◽  
Lidar Ratio ◽  
532 Nm

Abstract. In this paper, we report the first systematic comparison of 12-year modeled dust extinction profiles vs. Raman lidar measurements. We use the BSC-DREAM8b model, one of the most widely used dust regional models in the Mediterranean, and Potenza EARLINET lidar profiles for Saharan dust cases, the largest one-site database of dust extinction profiles. A total of 310 dust cases were compared for the May 2000–July 2012 period. The model reconstructs the measured layers well: profiles are correlated within 5% of significance for 60% of the cases and the dust layer center of mass as measured by lidar and modeled by BSC-DREAM8b differ on average 0.3 ± 1.0 km. Events with a dust optical depth lower than 0.1 account for 70% of uncorrelated profiles. Although there is good agreement in terms of profile shape and the order of magnitude of extinction values, the model overestimates the occurrence of dust layer top above 10 km. Comparison with extinction profiles measured by the Raman lidar shows that BSC-DREAM8b typically underestimates the dust extinction coefficient, in particular below 3 km. Lowest model–observation differences (below 17%) correspond to a lidar ratio at 532 nm and Ångström exponent at 355/532 nm of 60 ± 13 and 0.1 ± 0.6 sr, respectively. These are in agreement with values typically observed and modeled for pure desert dust. However, the highest differences (higher than 85%) are typically related to greater Ångström values (0.5 ± 0.6), denoting smaller particles. All these aspects indicate that the level of agreement decreases with an increase in mixing/modification processes.

scholarly journals Retrieval of aerosol microphysical properties from atmospheric lidar sounding: an investigation using synthetic measurements and data from the ACEPOL campaign

2021 ◽  
Vol 14 (6) ◽  
pp. 4755-4771
Author(s):  
William G. K. McLean ◽  
Guangliang Fu ◽  
Sharon P. Burton ◽  
Otto P. Hasekamp
Keyword(s):  
Refractive Index ◽  
Effective Radius ◽  
High Spectral Resolution ◽  
Imaginary Component ◽  
The Real ◽  
Microphysical Properties ◽  
Lidar Measurements ◽  
Fine Mode ◽  
Truth Value ◽  
Real Refractive Index

Abstract. This study presents an investigation of aerosol microphysical retrievals from high spectral resolution lidar (HSRL) measurements. Firstly, retrievals are presented for synthetically generated lidar measurements, followed by an application of the retrieval algorithm to real lidar measurements. Here, we perform the investigation for an aerosol state vector that is typically used in multi-angle polarimeter (MAP) retrievals, so that the results can be interpreted in relation to a potential combination of lidar and MAP measurements. These state vectors correspond to a bimodal size distribution, where column number, effective radius, and effective variance of both modes are treated as fit parameters, alongside the complex refractive index and particle shape. The focus is primarily on a lidar configuration based on that of the High Spectral Resolution Lidar-2 (HSRL-2), which participated in the ACEPOL (Aerosol Characterization from Polarimeter and Lidar) campaign, a combined project between NASA and SRON (Netherlands Institute for Space Research). The measurement campaign took place between October and November 2017, over the western region of the USA. Six different instruments were mounted on the aeroplane: four MAPs and two lidar instruments, HSRL-2 and the Cloud Physics Lidar (CPL). Most of the flights were carried out over land, passing over scenes with a low aerosol load. One of the flights passed over a prescribed forest fire in Arizona on 9 November, with a relatively higher aerosol optical depth (AOD), and it is the data from this flight that are focussed on in this study. A retrieval of the aerosol microphysical properties of the smoke plume mixture was attempted with the data from HSRL-2 and compared with a retrieval from the MAPs carried out in previous work pertaining to the ACEPOL data. The synthetic HSRL-2 retrievals resulted for the fine mode in a mean absolute error (MAE) of 0.038 (0.025) µm for the effective radius (with a mean truth value of 0.195 µm), 0.052 (0.037) for the real refractive index, 0.010 (7.20×10-3) for the imaginary part of the refractive index, 0.109 (0.071) for the spherical fraction, and 0.054 (0.039) for the AOD at 532 nm, where the retrievals inside brackets indicate the MAE for noise-free retrievals. For the coarse mode, we find the MAE is 0.459 (0.254) µm for the effective radius (with a mean truth value of 1.970 µm), 0.085 (0.075) for the real refractive index, 2.06×10-4 (1.90×10-4) for the imaginary component, 0.120 (0.090) for the spherical fraction, and 0.051 (0.039) for the AOD. A study of the sensitivity of retrievals to the choice of prior and first guess showed that, on average, the retrieval errors increase when the prior deviates too much from the truth value. These experiments revealed that the measurements primarily contain information on the size and shape of the aerosol, along with the column number. Some information on the real component of the refractive index is also present, with the measurements providing little on absorption or on the effective variance of the aerosol distribution, as both of these were shown to depend heavily on the choice of prior. Retrievals using the HSRL-2 smoke-plume data yielded, for the fine mode, an effective radius of 0.107 µm, a real refractive index of 1.561, an imaginary component of refractive index of 0.010, a spherical fraction of 0.719, and an AOD at 532 nm of 0.505. Additionally, the single-scattering albedo (SSA) from the HSRL-2 retrievals was 0.940. Overall, these results are in good agreement with those from the Spectropolarimeter for Planetary Exploration (SPEX) and Research Scanning Polarimeter (RSP) retrievals.

scholarly journals Retrieval of the tropospheric aerosol microphysical characteristics from the data of multifrequency lidar sensing

2018 ◽  
Vol 176 ◽  
pp. 05055 ◽  
Author(s):  
S. Samoilova ◽  
M. Sviridenkov ◽  
I. Penner ◽  
G. Kokhanenko ◽  
Yu. Balin
Keyword(s):  
Refractive Index ◽  
Distribution Function ◽  
Complex Refractive Index ◽  
Size Distribution Function ◽  
Coarse Fraction ◽  
Optical Parameters ◽  
Raman Lidar ◽  
Tropospheric Aerosol ◽  
Lidar Measurements ◽  
The Vertical Distribution

Regular lidar measurements of the vertical distribution of aerosol optical parameters are carried out in Tomsk (56°N, 85°E) since April, 2011. We present the results of retrieval of microphysical characteristics from the data of measurements by means of Raman lidar in 2013. Section 2 is devoted to the theoretical aspects of retrieving the particle size distribution function U(r) (SDF) assuming a known complex refractive index m (CRI). It is shown that the coarse fraction cannot be retrieved unambiguously. When estimating U(r) and m together (section 3), the retrieved refractive index is non-linearly related to the optical coefficients and the distribution function, which leads to appearance of different, including false values of m. The corresponding U(r) differs only slightly, so the inaccuracy in m does not essentially affect the retrieval of the distribution function.

scholarly journals Aerosol classification using airborne High Spectral Resolution Lidar measurements – methodology and examples

2012 ◽  
Vol 5 (1) ◽  
pp. 73-98 ◽  
Author(s):  
S. P. Burton ◽  
R. A. Ferrare ◽  
C. A. Hostetler ◽  
J. W. Hair ◽  
R. R. Rogers ◽  
...  
Keyword(s):  
Spectral Resolution ◽  
High Spectral Resolution ◽  
Color Ratio ◽  
Lidar Measurements ◽  
Aerosol Classification ◽  
Langley Research Center ◽  
High Spectral Resolution Lidar ◽  
Aerosol Types ◽  
532 Nm ◽  
Aerosol Type

Abstract. The NASA Langley Research Center (LaRC) airborne High Spectral Resolution Lidar (HSRL) on the NASA B200 aircraft has acquired extensive datasets of aerosol extinction (532 nm), aerosol optical depth (AOD) (532 nm), backscatter (532 and 1064 nm), and depolarization (532 and 1064 nm) profiles during 18 field missions that have been conducted over North America since 2006. The lidar measurements of aerosol intensive parameters (lidar ratio, depolarization, backscatter color ratio, and spectral depolarization ratio) are shown to vary with location and aerosol type. A methodology based on observations of known aerosol types is used to qualitatively classify the extensive set of HSRL aerosol measurements into eight separate types. Several examples are presented showing how the aerosol intensive parameters vary with aerosol type and how these aerosols are classified according to this new methodology. The HSRL-based classification reveals vertical variability of aerosol types during the NASA ARCTAS field experiment conducted over Alaska and northwest Canada during 2008. In two examples derived from flights conducted during ARCTAS, the HSRL classification of biomass burning smoke is shown to be consistent with aerosol types derived from coincident airborne in situ measurements of particle size and composition. The HSRL retrievals of AOD and inferences of aerosol types are used to apportion AOD to aerosol type; results of this analysis are shown for several experiments.

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 Retrieval of height-temporal distributions of particle parameters from multiwavelength lidar measurements using linear estimation technique and comparison results with AERONET

2013 ◽  
Vol 6 (2) ◽  
pp. 3059-3088 ◽  
Author(s):  
I. Veselovskii ◽  
D. N. Whiteman ◽  
M. Korenskiy ◽  
A. Kolgotin ◽  
O. Dubovik ◽  
...  
Keyword(s):  
Refractive Index ◽  
Effective Radius ◽  
Linear Estimation ◽  
Estimation Technique ◽  
Number Density ◽  
Volume Number ◽  
Lidar Measurements ◽  
Particle Parameters ◽  
Spatio Temporal ◽  
Multiwavelength Lidar

Abstract. The results of application of the linear estimation technique to multiwavelength Raman lidar measurements performed during the summer of 2011 in Greenbelt, MD, USA are presented. We demonstrate that multiwavelength lidars are capable not only of providing vertical profiles of particle properties but also of revealing the spatio-temporal evolution of aerosol features. The night-time 3β + 1α lidar measurements on 21 and 22 July were inverted to spatio-temporal distributions of particle microphysical parameters, such as volume, number density, effective radius and the complex refractive index. The particle volume and number density show strong variation during the night while the effective radius remains approximately constant. The real part of the refractive index demonstrates a slight decreasing tendency in a region of enhanced extinction coefficient. The linear estimation retrievals are stable and provide 2 min resolution time series of particle parameters at different heights. AERONET observations are compared with multiwavelength lidar retrievals showing good agreement.

Optical extinction from Raman lidar measurements

1996 ◽  
Author(s):  
Michael D. O'Brien ◽  
Tim D. Stevens ◽  
Franz Balsiger ◽  
C. Russell Philbrick
Keyword(s):  
Raman Lidar ◽  
Optical Extinction ◽  
Lidar Measurements

scholarly journals Retrieval of aerosol microphysical properties from atmospheric lidar sounding: an investigation using synthetic measurements and data from the ACEPOL campaign

2021 ◽  
Author(s):  
William G. K. McLean ◽  
Guangliang Fu ◽  
Sharon P. Burton ◽  
Otto P. Hasekamp
Keyword(s):  
Refractive Index ◽  
Effective Radius ◽  
High Spectral Resolution ◽  
Imaginary Component ◽  
The Real ◽  
Microphysical Properties ◽  
Lidar Measurements ◽  
Fine Mode ◽  
High Spectral Resolution Lidar ◽  
Real Refractive Index

Abstract. This study presents an investigation of aerosol microphysical retrievals from High Spectral Resolution Lidar (HSRL) measurements. Firstly, retrievals are presented for synthetically-generated lidar measurements, followed by an application of the retrieval algorithm to real lidar measurements. Here, we perform the investigation for an aerosol state vector that is typically used in multi-angle polarimeter (MAP) retrievals, so that the results can be interpreted in relation to a potential combination of lidar and MAP measurements. These state vectors correspond to a bimodal size distribution, where column number, effective radius, and effective variance of both modes are treated as fit parameters, alongside the complex refractive index and particle shape. The focus is primarily on a lidar configuration based on that of the High Spectral Resolution Lidar-2 (HSRL-2), which participated in the ACEPOL (Aerosol Characterization from Polarimeter and Lidar) campaign, a combined project between NASA and SRON (Netherlands Institute for Space Research). The measurement campaign took place between October and November 2017, over the western region of the USA. Six different instruments were mounted on the aeroplane: four MAPs, and two lidar instruments: HSRL-2, and the Cloud Physics Lidar (CPL). Most of the flights were carried out over land, passing over scenes with a low aerosol load. One of the flights passed over a prescribed forest fire in Arizona on the 9th of November, with a relatively higher AOD, and it is the data from this flight that is focussed on in this study. A retrieval of the aerosol microphysical properties of the smoke plume mixture was attempted with the data from HSRL-2, and compared with a retrieval from the MAPs carried out in previous work pertaining to the ACEPOL data. The synthetic HSRL-2 retrievals resulted for the fine mode in a mean absolute error (MAE) of 0.038 (0.025) μm for the effective radius, 0.052 (0.037) for the real refractive index, 0.010 (7.20 × 10−3) for the imaginary part of the refractive index, 0.109 (0.071) for the spherical fraction, and 0.054 (0.039) for the AOD at 532 nm, where the retrievals inside brackets indicate the MAE for noise-free retrievals. For the coarse mode, we find the MAE is 0.459 (0.254) μm for the effective radius, 0.085 (0.075) for the real refractive index, 2.06 × 10−4 (1.90 × 10−4) for the imaginary component, 0.120 (0.090) for the spherical fraction, and 0.051 (0.039) for the AOD. A study of the sensitivity of retrievals to the choice of prior and first guess showed that, on average, the retrieval errors increase when the prior deviates too much from the truth value. These experiments revealed that the measurements primarily contain information on the size and shape of the aerosol, along with the column number. Some information on the real component of the refractive index is also present, with the measurements providing little on absorption or on the effective variance of the aerosol distribution, as both of these were shown to depend heavily on the choice of prior. Retrievals using the HSRL-2 smoke-plume data yielded, for the fine mode, an effective radius of 0.107 μm, a real refractive index of 1.561, an imaginary component of refractive index of 0.010, a spherical fraction of 0.719, and an AOD at 532 nm of 0.505. Additionally, the single-scattering albedo (SSA) from the HSRL-2 retrievals was 0.940. Overall, these results are in good agreement with those from the SPEX and RSP retrievals.

scholarly journals Experimental assessment of the lidar polarizing sensitivity

2016 ◽  
Author(s):  
L. Belegante ◽  
J. A. Bravo-Aranda ◽  
V. Freudenthaler ◽  
D. Nicolae ◽  
A. Nemuc ◽  
...  
Keyword(s):  
Mass Concentration ◽  
Depolarization Ratio ◽  
Lidar System ◽  
Experimental Assessment ◽  
Ice Particles ◽  
Lidar Measurements ◽  
Extended Analysis ◽  
532 Nm ◽  
Main Factor ◽  
Depolarization Ratios

Abstract. Particle depolarization ratio retrieved from lidar measurements are commonly used for aerosol typing studies, microphysical inversion, or mass concentration retrievals. The particle depolarization ratio is one of the primary parameters that can differentiate several major aerosol components, but only if the measurements are accurate enough. The uncertainties related to the retrieval of particle depolarization ratios are the main factor in determining the accuracy of the derived parameters in such studies. This paper presents an extended analysis of different depolarization calibration procedures, in order to reduce the related uncertainties. The calibration procedures are specific to each lidar system of the European Aerosol Research Lidar Network – EARLINET with polarising capabilities. The results illustrate a significant improvement of the depolarization lidar products for all the selected lidar stations. The calibrated volume and particle depolarization profiles at 532 nm show values that agree with the theory for all selected atmospheric constituents (several aerosol species, ice particles and molecules in the aerosol free regions).

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