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 Optical characteristics of biomass burning aerosols over Southeastern Europe determined from UV-Raman lidar measurements

2009 ◽  
Vol 9 (7) ◽  
pp. 2431-2440 ◽  
Author(s):  
V. Amiridis ◽  
D. S. Balis ◽  
E. Giannakaki ◽  
A. Stohl ◽  
S. Kazadzis ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Hot Spot ◽  
Optical Parameters ◽  
Free Troposphere ◽  
Raman Lidar ◽  
Smoke Particles ◽  
Tropospheric Aerosol ◽  
Smoke Plumes ◽  
Lidar Measurements ◽  
Uv Raman

Abstract. The influence of smoke on the aerosol loading in the free troposphere over Thessaloniki, Greece is examined in this paper. Ten cases during 2001–2005 were identified when very high aerosol optical depth values in the free troposphere were observed with a UV-Raman lidar. Particle dispersion modeling (FLEXPART) and satellite hot spot fire detection (ATSR) showed that these high free tropospheric aerosol optical depths are mainly attributed to the advection of smoke plumes from biomass burning regions over Thessaloniki. The biomass burning regions were found to extend across Russia in the latitudinal belt between 45° N–55° N, as well as in Eastern Europe (Baltic countries, Western Russia, Belarus, and the Ukraine). The highest frequency of agricultural fires occurred during the summer season (mainly in August). The data collected allowed the optical characterization of the smoke aerosols that arrived over Greece, where limited information has so far been available. Two-wavelength backscatter lidar measurements showed that the backscatter-related Ångström exponent ranged between 0.5 and 2.4 indicating a variety of particle sizes. UV-Raman lidar measurements showed that for smoke particles the extinction to backscatter ratios (so-called lidar ratios) varied between 40 sr for small particles to 100 sr for large particles. Dispersion model estimations of the carbon monoxide tracer concentration profiles for smoke particles indicate that the variability of the optical parameters is a function of the age of the smoke plumes. This information could be useful on the lidar community for reducing uncertainty in the aerosol backscatter coefficient determination due to the lidar ratio assumption, starting from a simply elastic backscatter lidar as the first satellite-borne lidar CALIPSO.

scholarly journals Optical characteristics of biomass burning aerosols over Southeastern Europe determined from UV-Raman lidar measurements

2008 ◽  
Vol 8 (5) ◽  
pp. 18267-18293 ◽  
Author(s):  
V. Amiridis ◽  
D. S. Balis ◽  
E. Giannakaki ◽  
A. Stohl ◽  
S. Kazadzis ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Hot Spot ◽  
Optical Parameters ◽  
Free Troposphere ◽  
Raman Lidar ◽  
Smoke Particles ◽  
Tropospheric Aerosol ◽  
Smoke Plumes ◽  
Lidar Measurements ◽  
Uv Raman

Abstract. The influence of smoke on the aerosol loading in the free troposphere over Thessaloniki, Greece is examined in this paper. Ten cases during 2001–2005 were identified when very high aerosol optical depth values in the free troposphere were observed with a UV-Raman lidar. Particle dispersion modeling (FLEXPART) and satellite hot spot fire detection (ATSR) showed that these high free tropospheric aerosol optical depths are mainly attributed to the advection of smoke plumes from biomass burning regions over Thessaloniki. The biomass burning regions were found to extend across Russia in the latitudinal belt between 45° N–55° N, as well as in Eastern Europe (Baltic countries, Western Russia, Belarus, and the Ukraine). The highest frequency of agricultural fires occurred during the summer season (mainly in August). The data collected allowed the optical characterization of the smoke aerosols that arrived over Greece, where limited information has so far been available. Two-wavelength backscatter lidar measurements showed that the backscatter-related Ångström exponent ranged between 0.5 and 2.4 indicating a variety of particle sizes. UV-Raman lidar measurements showed that for smoke particles the extinction to backscatter ratios varied between 40 sr for small particles to 100 sr for large particles. Dispersion model estimations of the carbon monoxide tracer concentration profiles for smoke particles indicate that the variability of the optical parameters is a function of the age of the smoke plumes.

Study on the influence of different aerosol mixing states on lidar ratio

2020 ◽  
Author(s):  
zhijie zhang
Keyword(s):  
Refractive Index ◽  
Extinction Coefficient ◽  
Scale Parameter ◽  
Complex Refractive Index ◽  
Scattering Coefficient ◽  
Optical Parameters ◽  
Backscatter Signal ◽  
Back Scattering ◽  
Lidar Ratio ◽  
Mixing States

<p>             After years of development, Mie lidar has become an important technical means to explore aerosol particles in the atmosphere, and has been widely used to explore the optical and physical properties of aerosols in atmosphere. By Using backscatter signal collecting by lidar, optical characteristics of aerosols can be qualitatively analyzed. However, in order to get the actual value of optical parameters, the accurate lidar ratio (LR) (the ratio of extinction coefficient to back-scattering coefficient) is needed in inversion.</p><p>            Using the Mie scattering theory, the key parameter of inversion: LR, can be measured out. The value of LR has been discussed in detail by changing complex refractive index, size parameter  and field angle of a single particle. It is found that when the scale parameter is greater than 0.6, the value of LR increases first and then decreases with the increasing scale parameter, and there are several extremums; the value of LR decreases with the increasing imaginary part of the complex refractive index; the value of LR increases with the increasing filed angle.</p><p>            To study the influence of different mixing states on optical parameters of aerosol clusters, a three-component optical equilibrium spherical aerosol model is assumed. The results shows that when the mixing states of aerosol are complete external mixture, complete uniform internal mixture and complete coated mixture, the value of LR appears to be: complete uniform internal mixture > complete external mixture > complete coated mixture.</p><p>            Assuming that the hygroscopic growth factor of aerosol is a constant which does not increase with the particle size and its value is GF = 1.5[p2] , the value of LR after hygroscopic growing is discussed. It is found that the value of LR will increase after hygroscopic growing, but it still follows the law that: complete uniform internal mixture > complete external mixture > complete coated mixture.</p><p>            By correcting the value of LR, accurate extinction coefficient and back-scattering coefficient can be measured out with inversion. The production of lidar will be quantified instead of qualitative after doing this.</p>

scholarly journals One year of CNR-IMAA multi-wavelength Raman lidar measurements in correspondence of CALIPSO overpass: Level 1 products comparison

2009 ◽  
Vol 9 (2) ◽  
pp. 8429-8468 ◽  
Author(s):  
L. Mona ◽  
G. Pappalardo ◽  
A. Amodeo ◽  
G. D'Amico ◽  
F. Madonna ◽  
...  
Keyword(s):  
Relative Difference ◽  
Raman Lidar ◽  
Continental Scale ◽  
Tropospheric Aerosol ◽  
Lidar Measurements ◽  
Multi Wavelength ◽  
The Mean ◽  
Level 1 ◽  
The Difference ◽  
Mean Differences

Abstract. At CNR-IMAA, an aerosol lidar system is operative since May 2000 in the framework of EARLINET (European Aerosol Research Lidar Network), the first lidar network for tropospheric aerosol study on continental scale. High quality multi-wavelength measurements make this system a reference point for the validation of data products provided by CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations), the first satellite-borne lidar specifically designed for aerosol and cloud study. Since 14 June 2006, devoted measurements are performed at CNR-IMAA in coincidence of CALIPSO overpasses. For the first time, results on 1-year comparisons between ground-based multi-wavelength Raman lidar measurements and corresponding CALIPSO lidar Level 1 profiles are presented. A methodology for the comparison is presented and discussed into details. Cases with the detection of cirrus clouds in CALIPSO data are separately analysed for taking into account eventual multiple scattering effects. For cirrus cloud cases, few cases are available to draw any conclusions. For clear sky conditions, the comparison shows good performances of the CALIPSO on-board lidar: the mean relative difference between the ground-based and CALIPSO Level 1 measurements is always within its standard deviation at all altitudes, with a mean difference in the 3–8 km altitude range of (−2±12)%. At altitude ranges corresponding to the typical PBL height observed at CNR-IMAA, a mean underestimation of (−24±20)% is observed in CALIPSO data, probably due to the difference in the aerosol content at the location of PEARL and CALIPSO ground-track location. Finally, the mean differences are on average lower for the closest overpasses (at about 40 km), with an increment of the differences at all altitude ranges when the 80 km overpasses are considered.

Complex Refractive Index Dispersion of Strong Absorbing Material Determined Using Internal Reflectance Spectra Measurement

2018 ◽  
Vol 72 (9) ◽  
pp. 1349-1353 ◽  
Author(s):  
Zhichao Deng ◽  
Jin Wang ◽  
Zhixiong Hu ◽  
Jianchun Mei ◽  
Shike Liu ◽  
...  
Keyword(s):  
Refractive Index ◽  
Complex Refractive Index ◽  
Great Difficulty ◽  
Reflectance Spectra ◽  
Optical Parameters ◽  
Refractive Index Dispersion ◽  
Absorbing Material ◽  
Measuring Tool ◽  
Internal Reflectance

Complex refractive index dispersion (CRID) of offset inks is an important spectral property that affects the quality of printing. Due to the strong absorption of offset inks, great difficulty exists when measuring their CRID. In this study, a recently proposed apparatus that can detect the internal reflectance spectra was used to measure the CRID of three strong absorbing offset inks (magenta, yellow, and cyan). Both anomalous dispersion curve and extinction coefficient curve were well determined over the spectral range of 400–750 nm. This study experimentally proves that the apparatus and related method are feasible for the CRID measurement of strong absorbing materials and could serve as a powerful measuring tool for optical parameters.

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 Satellite retrieval of aerosol microphysical and optical parameters using neural networks: a new methodology applied to the Sahara desert dust peak

2013 ◽  
Vol 6 (6) ◽  
pp. 10955-11010
Author(s):  
M. Taylor ◽  
S. Kazadzis ◽  
A. Tsekeri ◽  
A. Gkikas ◽  
V. Amiridis
Keyword(s):  
Remote Sensing ◽  
Neural Networks ◽  
Refractive Index ◽  
Size Distribution ◽  
Aerosol Optical Depth ◽  
Principal Components ◽  
Complex Refractive Index ◽  
Remote Sensing Data ◽  
Optical Parameters ◽  
Desert Dust

Abstract. In order to exploit the full-Earth viewing potential of satellite instruments to globally characterise aerosols, new algorithms are required to deduce key microphysical parameters like the particle size distribution and optical parameters associated with scattering and absorption from space remote sensing data. Here, a methodology based on neural networks is developed to retrieve such parameters from satellite inputs and to validate them with ground-based remote sensing data. For key combinations of input variables available from MODIS and OMI Level 3 datasets, a grid of 100 feed-forward neural network architectures is produced, each having a different number of neurons and training proportion. The networks are trained with principal components accounting for 98% of the variance of the inputs together with principal components formed from 38 AERONET Level 2.0 (Version 2) retrieved parameters as outputs. Daily-averaged, co-located and synchronous data drawn from a cluster of AERONET sites centred on the peak of dust extinction in Northern Africa is used for network training and validation, and the optimal network architecture for each input parameter combination is identified with reference to the lowest mean squared error. The trained networks are then fed with unseen data at the coastal dust site Dakar to test their simulation performance. A NN, trained with co-located and synchronous satellite inputs comprising three aerosol optical depth measurements at 470, 500 and 660 nm, plus the columnar water vapour (from MODIS) and the modelled absorption aerosol optical depth at 500 nm (from OMI), was able to simultaneously retrieve the daily-averaged size distribution, the coarse mode volume, the imaginary part of the complex refractive index, and the spectral single scattering albedo – with moderate precision: correlation coefficients in the range 0.368 ≤ R ≤ 0.514. The network failed to recover the spectral behaviour of the real part of the complex refractive index with only 39–45% of the data falling within the acceptable level of uncertainty relative to ground-truth data at the daily timescale. In the context of Saharan desert dust, this new methodological approach appears to offer some potential for moderately accurate daily retrieval of previously inaccessible aerosol parameters from space.

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