On the spectral depolarisation and lidar ratio of mineral dust provided in the AERONET version 3 inversion product

Abstract. Knowledge of the particle lidar ratio (Sλ) and the particle linear depolarisation ratio (δλ) for different aerosol types allows for aerosol typing and aerosol-type separation in lidar measurements. Reference values generally originate from dedicated lidar observations but might also be obtained from the inversion of AErosol RObotic NETwork (AERONET) sun/sky radiometer measurements. This study investigates the consistency of spectral Sλ and δλ provided in the recently released AERONET version 3 inversion product for observations of undiluted mineral dust in the vicinity of the following major deserts: Gobi, Sahara, Arabian, Great Basin, and Great Victoria. Pure dust conditions are identified by an Ångström exponent <0.4 and a fine-mode fraction <0.1. The values of spectral Sλ are found to vary for the different source regions but generally show an increase with decreasing wavelength. The feature correlates to AERONET, retrieving an increase in the imaginary part of the refractive index with decreasing wavelength. The smallest values of Sλ=35–45 sr are found for mineral dust from the Great Basin desert, while the highest values of 50–70 sr have been inferred from AERONET observations of Saharan dust. Values of Sλ at 675, 870, and 1020 nm seem to be in reasonable agreement with available lidar observations, while those at 440 nm are up to 10 sr higher than the lidar reference. The spectrum of δλ shows a maximum of 0.26–0.31 at 1020 nm and decreasing values as wavelength decreases. AERONET-derived δλ values at 870 and 1020 nm are in line with the lidar reference, while values of 0.19–0.24 at 440 nm are smaller than the independent lidar observations by a difference of 0.03 to 0.08. This general behaviour is consistent with earlier studies based on AERONET version 2 products.

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Optical properties of different aerosol types: seven years of combined Raman-elastic backscatter lidar measurements in Thessaloniki, Greece

Atmospheric Measurement Techniques ◽

10.5194/amt-3-569-2010 ◽

2010 ◽

Vol 3 (3) ◽

pp. 569-578 ◽

Cited By ~ 60

Author(s):

E. Giannakaki ◽

D. S. Balis ◽

V. Amiridis ◽

C. Zerefos

Keyword(s):

Saharan Dust ◽

Downward Movement ◽

Angstrom Exponent ◽

Lidar Measurements ◽

Ångström Exponent ◽

Lidar Ratio ◽

Local Path ◽

Aerosol Types ◽

Lidar Observations ◽

Ångstrom Exponent

Abstract. We present our combined Raman/elastic backscatter lidar observations which were carried out at the EARLINET station of Thessaloniki, Greece, during the period 2001–2007. The largest optical depths are observed for Saharan dust and smoke aerosol particles. For local and continental polluted aerosols the measurements indicate high aerosol loads. However, measurements associated with the local path indicate enhanced aerosol load within the Planetary Boundary Layer. The lowest value of aerosol optical depth is observed for continental aerosols, from West directions with less free tropospheric contribution. The largest lidar ratios, of the order of 70 sr, are found for biomass burning aerosols. A significant and distinct correlation between lidar ratio and backscatter related Ångström exponent values were estimated for different aerosol categories. Scatter plot between lidar ratio values and Ångström exponent values for local and continental polluted aerosols does not show a significant correlation, with a large variation in both parameters possibly due to variable absorption characteristics of these aerosols. Finally for continental aerosols with west and northwest directions that follow downward movement when arriving at our site constantly low lidar ratios almost independent of size are found.

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Optical properties of different aerosol types: seven years of combined Raman- elastic backscatter lidar measurements in Thessaloniki, Greece

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-2-3027-2009 ◽

2009 ◽

Vol 2 (6) ◽

pp. 3027-3054

Author(s):

E. Giannakaki ◽

D. S. Balis ◽

V. Amiridis ◽

C. Zerefos

Keyword(s):

Saharan Dust ◽

Scatter Plot ◽

Angstrom Exponent ◽

Lidar Measurements ◽

Ångström Exponent ◽

Lidar Ratio ◽

Local Path ◽

Aerosol Types ◽

Lidar Observations ◽

Ångstrom Exponent

Abstract. We present our combined Raman/elastic backscatter lidar observations which were carried out at the EARLINET station of Thessaloniki, Greece, during the period 2001–2007. The largest optical depths are observed for Saharan dust and smoke aerosol loads. For "local" and "continental polluted" aerosols the measurements indicate moderate aerosol loads. However, measurements associated with the "local" path show lower values of free tropospheric contribution (37% versus 46% for "continental polluted") and thus, enhanced aerosol load within the Planetary Boundary Layer. The lowest value of aerosol optical depth is observed for "continental clean" aerosols. The largest lidar ratios, of the order of 70 sr are found for biomass burning aerosols. A significant and distinct correlation between lidar ratio and backscatter related Ångström exponent values was estimated for well defined aerosol categories, which provides a statistical measure of the lidar ratio's dependency on aerosol-size, which is a useful tool for elastic lidar systems. Scatter plot between lidar ratio values and Ångström exponent values for "local" and "continental polluted" aerosols does not show a significant correlation, with a large variation in both parameters possibly due to variable absorption characteristics of these aerosols. Finally for "clean continental" aerosols we found constantly low lidar ratios almost independent of size.

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Investigating emission sources and transport of aerosols in Siberia using airborne and spaceborne LIDAR measurements

10.5194/acp-2020-195 ◽

2020 ◽

Author(s):

Antonin Zabukovec ◽

Gerard Ancellet ◽

Iwan E. Penner ◽

Mikhail Arshinov ◽

Valery Kozlov ◽

...

Keyword(s):

Optical Depth ◽

Forest Fire ◽

Airborne Lidar ◽

Aerosol Layer ◽

Gas Flaring ◽

Fire Plumes ◽

Lidar Measurements ◽

Lidar Ratio ◽

Aerosol Types ◽

Aerosol Type

Abstract. Airborne backscatter lidar measurements at 532 nm were carried out over Siberia in July 2013 and June 2017. The Russian Tu-134 flew over major Siberian cities (Novosibirsk, Tomsk, Krasnoyarsk, Yakutsk), the gas flaring fields of the Ob valley and Siberian Taiga in order to sample several kinds of Siberian aerosol sources. Aerosol types are derived using the Lagrangian FLEXible PARTicle dispersion model (FLEXPART) simulations, Moderate Resolution Imaging Spectrometer (MODIS) Aerosol Optical Depth (AOD), Infrared Atmospheric Sounding Interferometer (IASI) CO total column and AOD at 10 μm. Forest fire detection is based on NASA Fire Information for Resource Management System (FIRMS) from MODIS and the Visible Infrared Imaging Radiometer Suite (VIIRS) observations and airborne in-situ measurements when available. Six aerosol type could be identified in this work: (i) Dusty aerosol mixture (ii) Ob valley industrial emission (iii) fresh boreal forest fire plumes (iv) aged forest fire plumes (v) pollution over the Tomsk/Novosibirsk region (vi) long range transport of Chinese pollution over Yakutsk. The backscatter to extinction ratio and then the corresponding lidar ratio (LR) were derived for each of these 6 identified aerosol type, using an iterative method based on the Fernald forward inversion constrained by the 10 km MODIS collection 6 AOD distribution closed to the airborne lidar observation. The LR analysis showed that the lowest LR range was obtained for the Dusty Mix case (26–40 sr) and the highest for the urban and industrial pollution from the Tomsk/Novosibirsk area (71–90 sr). The comparison is good with previous estimate of LR according to the aerosol classification. The range of lidar ratio obtained for gas flaring emission (43–60 sr) was lower than the high values encountered in the Tomsk/Novosibirk urban area and has never been characterized using lidar observations. Airborne lidar backscatter ratio vertical structure, aerosol types and integrated LR derived from the airborne data analysis were compared to nearby CALIOP overpasses. These comparisons showed three main differences with the CALIOP LR and aerosol type classification over Siberia: (i) CALIOP aerosol layer can be classified as Elevated smoke instead of Polluted continental and vice versa, but with little influence on the LR value (ii) aging and transport of aerosol layers effect on the CALIOP LR value is not always properly accounted for even when the CALIOP classification is correct (iii) the lack of discrimination between fresh and old fire plume leads to an overestimation of the optical depth for the fresh fires in the CALIOP AOD over the fire source region.

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Airborne high spectral resolution lidar observation of pollution aerosol during EUCAARI-LONGREX

Atmospheric Chemistry and Physics ◽

10.5194/acp-13-2435-2013 ◽

2013 ◽

Vol 13 (5) ◽

pp. 2435-2444 ◽

Cited By ~ 14

Author(s):

S. Groß ◽

M. Esselborn ◽

F. Abicht ◽

M. Wirth ◽

A. Fix ◽

...

Keyword(s):

Spectral Resolution ◽

High Spectral Resolution ◽

Data Set ◽

Lidar Ratio ◽

Linear Depolarization Ratio ◽

High Spectral Resolution Lidar ◽

Aerosol Types ◽

Lidar Observations ◽

Aerosol Type

Abstract. Airborne high spectral resolution lidar observations over Europe during the EUCAARI-LONGREX field experiment in May 2008 are analysed with respect to the optical properties of continental pollution aerosol. Continental pollution aerosol is characterized by its depolarisation and lidar ratio. Over all, the measurements of the lidar ratio and the particle linear depolarization ratio of pollution aerosols provide a narrow range of values. Therefore, this data set allows for a distinct characterization of the aerosol type "pollution aerosol" and thus is valuable both to distinguish continental pollution aerosol from other aerosol types and to determine mixtures with other types of aerosols.

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Aerosol classification from airborne HSRL and comparisons with the CALIPSO vertical feature mask

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-6-1815-2013 ◽

2013 ◽

Vol 6 (1) ◽

pp. 1815-1858 ◽

Cited By ~ 10

Author(s):

S. P. Burton ◽

R. A. Ferrare ◽

M. A. Vaughan ◽

A. H. Omar ◽

R. R. Rogers ◽

...

Keyword(s):

High Spectral Resolution ◽

Dependent Observations ◽

Aerosol Retrieval ◽

Direct Measurements ◽

Aerosol Classification ◽

Lidar Ratio ◽

Langley Research Center ◽

High Spectral Resolution Lidar ◽

Aerosol Types ◽

Aerosol Type

Abstract. Aerosol classification products from the NASA Langley Research Center (LaRC) airborne High Spectral Resolution Lidar (HSRL-1) on the NASA B200 aircraft are compared with coincident V3.01 aerosol classification products from the CALIOP instrument on the CALIPSO satellite. For CALIOP, aerosol classification is a key input to the aerosol retrieval, and must be inferred using aerosol loading-dependent observations and location information. In contrast, HSRL-1 makes direct measurements of aerosol intensive properties, including the lidar ratio, that provide information on aerosol type. In this study, comparisons are made for 109 underflights of the CALIOP orbit track. We find that 62% of the CALIOP marine layers and 54% of the polluted continental layers agree with HSRL-1 classification results. In addition, 80% of the CALIOP desert dust layers are classified as either dust or dusty mix by HSRL-1. However, agreement is less for CALIOP smoke (13%) and polluted dust (35%) layers. Specific case studies are examined, giving insight into the performance of the CALIOP aerosol type algorithm. In particular, we find that the CALIOP polluted dust type is overused due to an attenuation-related depolarization bias. Furthermore, the polluted dust type frequently includes mixtures of dust plus marine aerosol. Finally, we find that CALIOP's identification of internal boundaries between different aerosol types in contact with each other frequently do not reflect the actual transitions between aerosol types accurately. Based on these findings, we give recommendations which may help to improve the CALIOP aerosol type algorithms.

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Assessment of tropospheric CALIPSO Version 4.2 aerosol types over the ocean using independent CALIPSO-SODA lidar ratios

10.5194/amt-2021-378 ◽

2021 ◽

Author(s):

Zhujun Li ◽

David Painemal ◽

Gregory Schuster ◽

Marian Clayton ◽

Richard Ferrare ◽

...

Keyword(s):

Optical Depth ◽

Classification Scheme ◽

Signal To Noise Ratio ◽

Open Ocean ◽

African Continent ◽

Marine Aerosols ◽

Lidar Ratio ◽

Aerosol Plume ◽

Aerosol Types ◽

Aerosol Type

Abstract. We assess the CALIPSO Version 4.2 (V4) aerosol typing and assigned lidar ratios over ocean using aerosol optical depth (AOD) retrievals from the Synergized Optical Depth of Aerosols (SODA) algorithm and retrieved columnar lidar ratio estimated by combining SODA AOD and CALIPSO attenuated backscatter (CALIPSO-SODA). Six aerosol types – clean marine, dusty marine, dust, polluted continental/smoke, polluted dust, and elevated smoke – are characterized using CALIPSO-SODA over ocean and the results are compared against the prescribed V4 lidar ratios, when only one aerosol type is present in the atmospheric column. For samples detected at 5-km or 20-km spatial resolutions and having AOD > 0.05, the CALIPSO-SODA lidar ratios are significantly different between different aerosol types, and are consistent with the type-specific values assigned in V4 to within 10 sr (except for polluted continental/smoke). This implies that the CALIPSO classification scheme generally categorizes aerosols correctly. We find remarkable daytime/nighttime regional agreement for clean marine aerosol over the open ocean (CALIPSO-SODA = 20–25 sr, V4 = 23 sr), elevated smoke over the southeast Atlantic (CALIPSO-SODA = 65–75 sr, V4 = 70 sr), and dust over the subtropical Atlantic adjacent to the African continent (CALIPSO-SODA = 40–50 sr, V4 = 44 sr). In contrast, daytime polluted continental/smoke lidar ratio is more than 20 sr smaller than the constant V4 vaue for that type, attributed in part to the challenge of classifying tenuous aerosol with low signal-to-noise ratio. Dust over most of the Atlantic Ocean features CALIPSO-SODA lidar ratios less than 40 sr, possibly suggesting the presence of dust mixed with marine aerosols or lidar ratio values that depend on source and evolution of the aerosol plume. The new dusty marine type introduced in V4 features similar magnitudes and spatial distribution as its clean marine counterpart with lidar ratio differences of less than 3 sr, and nearly identical values over the open ocean, implying that some modification of the classification scheme for the marine subtypes is warranted.

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

Atmospheric Measurement Techniques ◽

10.5194/amt-5-73-2012 ◽

2012 ◽

Vol 5 (1) ◽

pp. 73-98 ◽

Cited By ~ 252

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.

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The potential of elastic and polarization lidars to retrieve extinction profiles

Atmospheric Measurement Techniques ◽

10.5194/amt-13-893-2020 ◽

2020 ◽

Vol 13 (2) ◽

pp. 893-905 ◽

Cited By ~ 5

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.

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Aerosol-type classification based on AERONET version 3 inversion products

Atmospheric Measurement Techniques ◽

10.5194/amt-12-3789-2019 ◽

2019 ◽

Vol 12 (7) ◽

pp. 3789-3803 ◽

Cited By ~ 12

Author(s):

Sung-Kyun Shin ◽

Matthias Tesche ◽

Youngmin Noh ◽

Detlef Müller

Keyword(s):

East Asia ◽

Biomass Burning ◽

Mineral Dust ◽

Anthropogenic Pollution ◽

Single Scattering ◽

Asian Dust ◽

Dust Particles ◽

Aerosol Types ◽

Type Classification ◽

Aerosol Type

Abstract. This study proposes an aerosol-type classification based on the particle linear depolarization ratio (PLDR) and single-scattering albedo (SSA) provided in the AErosol RObotic NETwork (AERONET) version 3 level 2.0 inversion product. We compare our aerosol-type classification with an earlier method that uses fine-mode fraction (FMF) and SSA. Our new method allows for a refined classification of mineral dust that occurs as a mixture with other absorbing aerosols: pure dust (PD), dust-dominated mixed plume (DDM), and pollutant-dominated mixed plume (PDM). We test the aerosol classification at AERONET sites in East Asia that are frequently affected by mixtures of Asian dust and biomass-burning smoke or anthropogenic pollution. We find that East Asia is strongly affected by pollution particles with high occurrence frequencies of 50 % to 67 %. The distribution and types of pollution particles vary with location and season. The frequency of PD and dusty aerosol mixture (DDM+PDM) is slightly lower (34 % to 49 %) than pollution-dominated mixtures. Pure dust particles have been detected in only 1 % of observations. This suggests that East Asian dust plumes generally exist in a mixture with pollution aerosols rather than in pure form. In this study, we have also considered data from selected AERONET sites that are representative of anthropogenic pollution, biomass-burning smoke, and mineral dust. We find that average aerosol properties obtained for aerosol types in our PLDR–SSA-based classification agree reasonably well with those obtained at AERONET sites representative for different aerosol types.

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