LIVAS: a 3-D multi-wavelength aerosol/cloud database based on CALIPSO and EARLINET

Abstract. We present LIVAS (LIdar climatology of Vertical Aerosol Structure for space-based lidar simulation studies), a 3-D multi-wavelength global aerosol and cloud optical database, optimized to be used for future space-based lidar end-to-end simulations of realistic atmospheric scenarios as well as retrieval algorithm testing activities. The LIVAS database provides averaged profiles of aerosol optical properties for the potential spaceborne laser operating wavelengths of 355, 532, 1064, 1570 and 2050 nm and of cloud optical properties at the wavelength of 532 nm. The global database is based on CALIPSO observations at 532 and 1064 nm and on aerosol-type-dependent backscatter- and extinction-related Ångström exponents, derived from EARLINET (European Aerosol Research Lidar Network) ground-based measurements for the UV and scattering calculations for the IR wavelengths, using a combination of input data from AERONET, suitable aerosol models and recent literature. The required spectral conversions are calculated for each of the CALIPSO aerosol types and are applied to CALIPSO backscatter and extinction data corresponding to the aerosol type retrieved by the CALIPSO aerosol classification scheme. A cloud optical database based on CALIPSO measurements at 532 nm is also provided, neglecting wavelength conversion due to approximately neutral scattering behavior of clouds along the spectral range of LIVAS. Averages of particle linear depolarization ratio profiles at 532 nm are provided as well. Finally, vertical distributions for a set of selected scenes of specific atmospheric phenomena (e.g., dust outbreaks, volcanic eruptions, wild fires, polar stratospheric clouds) are analyzed and spectrally converted so as to be used as case studies for spaceborne lidar performance assessments. The final global data set includes 4-year (1 January 2008–31 December 2011) time-averaged CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) data on a uniform grid of 1° × 1° with the original high vertical resolution of CALIPSO in order to ensure realistic simulations of the atmospheric variability in lidar end-to-end simulations.

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LIVAS: a 3-D multi-wavelength aerosol/cloud climatology based on CALIPSO and EARLINET

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-15-2247-2015 ◽

2015 ◽

Vol 15 (2) ◽

pp. 2247-2304 ◽

Cited By ~ 5

Author(s):

V. Amiridis ◽

E. Marinou ◽

A. Tsekeri ◽

U. Wandinger ◽

A. Schwarz ◽

...

Keyword(s):

Optical Properties ◽

Volcanic Eruptions ◽

Retrieval Algorithm ◽

Uniform Grid ◽

Conversion Factors ◽

Multi Wavelength ◽

End To End ◽

532 Nm ◽

Aerosol Type ◽

Spectral Conversion

Abstract. We present LIVAS, a 3-dimentional multi-wavelength global aerosol and cloud optical climatology, optimized to be used for future space-based lidar end-to-end simulations of realistic atmospheric scenarios as well as retrieval algorithm testing activities. LIVAS database provides averaged profiles of aerosol optical properties for the potential space-borne laser operating wavelengths of 355, 532, 1064, 1570 and 2050 nm and of cloud optical properties at the wavelength of 532 nm. The global climatology is based on CALIPSO observations at 532 and 1064 nm and on aerosol-type-dependent spectral conversion factors for backscatter and extinction, derived from EARLINET ground-based measurements for the UV and scattering calculations for the IR wavelengths, using a combination of input data from AERONET, suitable aerosol models and recent literature. The required spectral conversion factors are calculated for each of the CALIPSO aerosol types and are applied to CALIPSO extinction and backscatter data correspondingly to the aerosol type retrieved by the CALIPSO aerosol classification scheme. A cloud climatology based on CALIPSO measurements at 532 nm is also provided, neglecting wavelength conversion due to approximately neutral scattering behavior of clouds along the spectral range of LIVAS. Averages of particle linear depolarization ratio profiles at 532 nm are provided as well. Finally, vertical distributions for a set of selected scenes of specific atmospheric phenomena (e.g., dust outbreaks, volcanic eruptions, wild fires, polar stratospheric clouds) are analyzed and spectrally converted so as to be used as case studies for space-borne lidar performance assessments. The final global climatology includes 4-year (1 January 2008–31 December 2011) time-averaged CALIPSO data on a uniform grid of 1×1 degree with the original high vertical resolution of CALIPSO in order to ensure realistic simulations of the atmospheric variability in lidar end-to-end simulations.

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OMPS LP Version 2.0 Multi-wavelength Aerosol Extinction Coefficient Retrieval Algorithm

10.5194/amt-2020-329 ◽

2020 ◽

Author(s):

Ghassan Taha ◽

Robert Loughman ◽

Tong Zhu ◽

Larry Thomason ◽

Jayanta Kar ◽

...

Keyword(s):

Extinction Coefficient ◽

Volcanic Eruptions ◽

Retrieval Algorithm ◽

Aerosol Extinction ◽

Data Set ◽

Detection And Tracking ◽

Accuracy And Precision ◽

Multi Wavelength ◽

Version 2.0 ◽

Aerosol Extinction Coefficient

Abstract. The OMPS Limb Profiler (LP) instrument is designed to provide high vertical resolution ozone and aerosol profiles from measurements of the scattered solar radiation in the 290–1000 nm spectral range. It collected its first Earth limb measurement on January 10, 2012 and continues to provide daily global measurements of ozone and aerosol profiles from the cloud top up to 60 km and 40 km respectively. The relatively high vertical and spatial sampling allow detection and tracking of sporadic events when aerosol particles are injected into the stratosphere, such as volcanic eruptions or PyroCb events. In this paper we discuss the newly released Version 2.0 OMPS multi-wavelength aerosol extinction coefficient retrieval algorithm. The algorithm now produces aerosol extinction profiles at 510, 600, 674, 745, 869, and 997 nm wavelengths. The OMPS LP Version 2.0 data products are compared to the SAGE III/ISS, OSIRIS and CALIPSO missions and shown to be of good quality and suitable for scientific studies. The comparison shows significant improvements in the OMPS LP retrieval performance in the Southern Hemisphere and at lower altitudes. These improvements arise from use of the longer wavelengths, in contrast with the V1.0 and V1.5 OMPS aerosol retrieval algorithms, which used radiances only at 675 nm and therefore had limited sensitivity in those regions. In particular, the extinction coefficients at 745, 869 and 997 nm are shown to be the most accurate, with relative accuracies and precisions close to 10 % and 15 % respectively, while the 675 nm relative accuracy and precision are on the order of 20 %. The 510 nm extinction coefficient is shown to have limited accuracy in SH and is only recommended for use between 20–24 km, and only in the Northern Hemisphere. The V2.0 retrieval algorithm has been applied to the complete set of OMPS LP measurements and the new data set is publicly available.

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Optical properties of Central Asian aerosol relevant for spaceborne lidar applications and aerosol typing at 355 and 532 nm

10.5194/acp-2020-258 ◽

2020 ◽

Cited By ~ 2

Author(s):

Julian Hofer ◽

Albert Ansmann ◽

Dietrich Althausen ◽

Ronny Engelmann ◽

Holger Baars ◽

...

Keyword(s):

Optical Properties ◽

Full Range ◽

Anthropogenic Pollution ◽

Data Set ◽

Central Asian ◽

Lidar Ratio ◽

Ground Based Lidar ◽

Complex Relationships ◽

532 Nm ◽

Depolarization Ratios

Abstract. For the first time, a dense data set of particle extinction-to-backscatter ratios (lidar ratios), linear depolarization ratios, and backscatter- and extinction-related Ångström exponents for a Central Asian site are presented. The observations were performed with a continuously running multiwavelength polarization Raman lidar at Dushanbe, Tajikistan, during an 18-month campaign (March 2015 to August 2016). The presented seasonally resolved observations fill an important gap in the data base of aerosol optical properties used in aerosol typing efforts with spaceborne lidars and ground-based lidar networks. Lidar ratios and depolarization ratios are also basic input parameters in spaceborne lidar data analyses and in efforts to harmonize long-term observations with different space lidar systems operated either at 355 or 532 nm. As a general result, the found optical properties reflect the large range of occurring aerosol mixtures consisting of long-range-transported dust (from the Middle East and the Sahara), regional desert, soil, and salt dust, and anthropogenic pollution. The full range from highly polluted to pure dust situations could be observed. Typical dust depolarization ratios of 0.23–0.29 (355 nm) and 0.30–0.35 (532 nm) were observed. In contrast, comparably low lidar ratios were found. Dust lidar ratios at 532 nm accumulated around 35–40 sr and were even lower for regional background dust conditions (20–30 sr). The reason for these low values may be partly related to the direct emission and emission of re-suspended salt dust (initially originated from numerous desiccating lakes and the Aralkum desert). Detailed correlation studies (e.g., lidar ratio vs. depolarization ratios and Ångström exponent vs. lidar ratio and vs. depolarization ratio) are presented to illuminate the complex relationships between the observed optical properties and to identify the contributions of anthropogenic haze, dust, and background aerosol to the overall aerosol mixtures found within the 18-month campaign.

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Aerosol type classification analysis using EARLINET multiwavelength and depolarization lidar observations

Atmospheric Chemistry and Physics ◽

10.5194/acp-21-2211-2021 ◽

2021 ◽

Vol 21 (3) ◽

pp. 2211-2227

Author(s):

Maria Mylonaki ◽

Elina Giannakaki ◽

Alexandros Papayannis ◽

Christina-Anna Papanikolaou ◽

Mika Komppula ◽

...

Keyword(s):

Optical Properties ◽

Lower Percentage ◽

Optical Parameters ◽

Full Data ◽

Data Set ◽

Classification Analysis ◽

Tropospheric Aerosol ◽

Aerosol Classification ◽

Type Classification ◽

Aerosol Type

Abstract. We introduce an automated aerosol type classification method, called Source Classification Analysis (SCAN). SCAN is based on predefined and characterized aerosol source regions, the time that the air parcel spends above each geographical region, and a number of additional criteria. The output of SCAN is compared with two independent aerosol classification methods, which use the intensive optical parameters from lidar data: (1) the Mahalanobis distance automatic aerosol type classification (MD) and (2) a neural network aerosol typing algorithm (NATALI). In this paper, data from the European Aerosol Research Lidar Network (EARLINET) have been used. A total of 97 free tropospheric aerosol layers from four typical EARLINET stations (i.e., Bucharest, Kuopio, Leipzig, and Potenza) in the period 2014–2018 were classified based on a 3β+2α+1δ lidar configuration. We found that SCAN, as a method independent of optical properties, is not affected by overlapping optical values of different aerosol types. Furthermore, SCAN has no limitations concerning its ability to classify different aerosol mixtures. Additionally, it is a valuable tool to classify aerosol layers based on even single (elastic) lidar signals in the case of lidar stations that cannot provide a full data set (3β+2α+1δ) of aerosol optical properties; therefore, it can work independently of the capabilities of a lidar system. Finally, our results show that NATALI has a lower percentage of unclassified layers (4 %), while MD has a higher percentage of unclassified layers (50 %) and a lower percentage of cases classified as aerosol mixtures (5 %).

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Optical properties of Central Asian aerosol relevant for spaceborne lidar applications and aerosol typing at 355 and 532 nm

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-9265-2020 ◽

2020 ◽

Vol 20 (15) ◽

pp. 9265-9280 ◽

Cited By ~ 3

Author(s):

Julian Hofer ◽

Albert Ansmann ◽

Dietrich Althausen ◽

Ronny Engelmann ◽

Holger Baars ◽

...

Keyword(s):

Optical Properties ◽

Full Range ◽

Anthropogenic Pollution ◽

Data Set ◽

Central Asian ◽

Lidar Ratio ◽

Ground Based Lidar ◽

Complex Relationships ◽

532 Nm ◽

Depolarization Ratios

Abstract. For the first time, a dense data set of particle extinction-to-backscatter ratios (lidar ratios), linear depolarization ratios, and backscatter- and extinction-related Ångström exponents for a Central Asian site are presented. The observations were performed with a continuously running multiwavelength polarization Raman lidar at Dushanbe, Tajikistan, during an 18-month campaign (March 2015 to August 2016). The presented seasonally resolved observations fill an important gap in the database of aerosol optical properties used in aerosol typing efforts with spaceborne lidars and ground-based lidar networks. Lidar ratios and depolarization ratios are also basic input parameters in spaceborne lidar data analyses and in efforts to harmonize long-term observations with different space lidar systems operated at either 355 or 532 nm. As a general result, the found optical properties reflect the large range of occurring aerosol mixtures consisting of long-range-transported dust (from the Middle East and the Sahara), regional desert, soil, and salt dust, and anthropogenic pollution. The full range from highly polluted to pure dust situations could be observed. Typical dust depolarization ratios of 0.23–0.29 (355 nm) and 0.30–0.35 (532 nm) were observed. In contrast, comparably low lidar ratios were found. Dust lidar ratios at 532 nm accumulated around 35–40 sr and were even lower for regional background dust conditions (20–30 sr). Detailed correlation studies (e.g., lidar ratio vs. depolarization ratios, Ångström exponent vs. lidar ratio and vs. depolarization ratio) are presented to illuminate the complex relationships between the observed optical properties and to identify the contributions of anthropogenic haze, dust, and background aerosol to the overall aerosol mixtures found within the 18-month campaign. The observation of 532 nm lidar ratios (<25 sr) and depolarization ratios (around 15 %–20 %) in layers with very low particle extinction coefficient (<30 sr) suggests that direct emission and emission of resuspended salt dust (initially originated from numerous desiccating lakes and the Aralkum desert) have a sensitive impact on the aerosol background optical properties over Dushanbe.

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Aerosol optical properties variability during biomass burning events observed by the eole-aias depolarization lidars over Athens, Greece (2007-2016)

EPJ Web of Conferences ◽

10.1051/epjconf/201817605022 ◽

2018 ◽

Vol 176 ◽

pp. 05022

Author(s):

Maria Mylonaki ◽

Alexandros Papayannis ◽

Rodanthi Mamouri ◽

Athina Argyrouli ◽

Panagiotis Kokkalis ◽

...

Keyword(s):

Optical Properties ◽

Biomass Burning ◽

Vertical Profiles ◽

Aerosol Optical Properties ◽

Smoke Particles ◽

Range Transport ◽

Multi Wavelength ◽

Lidar Ratio ◽

Sun Photometer ◽

532 Nm

The EOLE multi-wavelength aerosol Ramandepolarization lidar, and the AIAS depolarization lidar, in synergy with a sun photometer (CIMEL), were used, in the period 2007-2016, to provide the vertical profiles of the aerosol optical properties over Athens, Greece. More than 30 biomass burning events (fresh and aged smoke particles) were observed, with smoke layers between 1.5 up to 4-5 km height, while their duration ranged from 1-3 days. Lidar ratio (LR) values ranged from 40-105 sr (at 355 nm) and from 40-100 sr (at 532 nm), while the linear particle depolarization ratio (LPDR) at both 355 and 532 nm, remained <7%. The extinction-related Ångström exponent (AEa) at 355 nm/532 nm) ranged from 0.3 to 2.1. Additionally, a case of a near-range transport of biomass burning aerosols arriving over Athens up to 4 km height, between 27 and 28 June 2016, was studied. For this case, we found LRs of the order of 70±5 sr (355 nm) and 65±15 sr (532 nm) and AEa(355 nm/532 nm) around 1.

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Biomass burning aerosols characterization from ground based and profiling measurements

EPJ Web of Conferences ◽

10.1051/epjconf/201817608013 ◽

2018 ◽

Vol 176 ◽

pp. 08013

Author(s):

Cristina Marin ◽

Jeni Vasilescu ◽

Luminita Marmureanu ◽

Dragos Ene ◽

Liliana Preda ◽

...

Keyword(s):

Optical Properties ◽

Chemical Composition ◽

Biomass Burning ◽

Chemical Speciation ◽

Low Level ◽

Lidar Measurements ◽

Organic Markers ◽

Multi Wavelength ◽

Aerosol Type

The study goal is to assess the chemical and optical properties of aerosols present in the lofted layers and at the ground. The biomass burning aerosols were evaluated in low level layers from multi-wavelength lidar measurements, while chemical composition at ground was assessed using an Aerosol Chemical Speciation Monitor (ACSM) and an Aethalometer. Classification of aerosol type and specific organic markers were used to explore the potential to sense the particles from the same origin at ground base and on profiles.

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Properties of biomass burning aerosol mixtures derived at fine temporal and spatial scales from Raman lidar measurements: Part I optical properties

10.5194/acp-2019-207 ◽

2019 ◽

Cited By ~ 5

Author(s):

Lucja Janicka ◽

Iwona S. Stachlewska

Keyword(s):

Optical Properties ◽

Biomass Burning ◽

Spatial Scales ◽

Depolarization Ratio ◽

Data Set ◽

Lidar Ratio ◽

Biomass Burning Aerosol ◽

The Mean ◽

Temporal And Spatial ◽

532 Nm

Abstract. The analysis of the aerosol optical properties derived at fine temporal and spatial scales were performed based on measurements obtained during heat wave event in vicinity of a cold weather front in Warsaw on August 9th–11th, 2015. The signals collected by the PollyXT-UW lidar allowed for the calculation of 23 sets of so-called 3β + 2α + 2δ + wv profiles averaged by 30-minutes periods during 2 nights. The total number of 11 different aerosol types and aerosol mixtures were identified with reference to properties within 116 sub-layers in the profiles and were characterized by the mean values. The statistical sample of various optical properties being in agreement for consecutive profiles allowed to assess the spatio-temporal extent of aerosol/mixture types. The mean lidar ratio values of 53–73 sr (355 nm) and 31–45 sr (532 nm) in the layers dominated by the anthropogenic pollution were found. For the layers dominated by the biomass burning aerosol (fresh, moderately fresh, moderately aged) mean lidar ratio was of 69–114 sr (355 nm) and 57–85 sr (532 nm). The colour ratio of lidar ratio (532 / 355) higher than 1, characteristic for aged biomass burning aerosol, was found only in one scattered layer, accompanying with low value of extinction related Ångström exponent of 0.60 ± 0.32 and low particle depolarization ratio. The maximum of the particle depolarization ratio of 4.8–5.0 % at 532 nm were observed in a layer likely contaminated with pollen and in a layer dominated by fresh biomass burning aerosol. This study provides an excellent data set for exploration of separation algorithms, aerosol typing algorithms and microphysical inversion.

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OMPS LP Version 2.0 multi-wavelength aerosol extinction coefficient retrieval algorithm

Atmospheric Measurement Techniques ◽

10.5194/amt-14-1015-2021 ◽

2021 ◽

Vol 14 (2) ◽

pp. 1015-1036

Author(s):

Ghassan Taha ◽

Robert Loughman ◽

Tong Zhu ◽

Larry Thomason ◽

Jayanta Kar ◽

...

Keyword(s):

Extinction Coefficient ◽

Volcanic Eruptions ◽

Retrieval Algorithm ◽

Aerosol Extinction ◽

Detection And Tracking ◽

Accuracy And Precision ◽

Multi Wavelength ◽

High Vertical Resolution ◽

Version 2.0 ◽

Aerosol Extinction Coefficient

Abstract. The OMPS Limb Profiler (LP) instrument is designed to provide high-vertical-resolution ozone and aerosol profiles from measurements of the scattered solar radiation in the 290–1000 nm spectral range. It collected its first Earth limb measurement on 10 January 2012 and continues to provide daily global measurements of ozone and aerosol profiles from the cloud top up to 60 and 40 km, respectively. The relatively high vertical and spatial sampling allow detection and tracking of sporadic events when aerosol particles are injected into the stratosphere, such as volcanic eruptions or pyrocumulonimbus (PyroCb) events. In this paper we discuss the newly released Version 2.0 OMPS multi-wavelength aerosol extinction coefficient retrieval algorithm. The algorithm now produces aerosol extinction profiles at 510, 600, 674, 745, 869 and 997 nm wavelengths. The OMPS LP Version 2.0 data products are compared to the SAGE III/ISS, OSIRIS and CALIPSO missions and shown to be of good quality and suitable for scientific studies. The comparison shows significant improvements in the OMPS LP retrieval performance in the Southern Hemisphere (SH) and at lower altitudes. These improvements arise from use of the longer wavelengths, in contrast with the V1.0 and V1.5 OMPS aerosol retrieval algorithms, which used radiances only at 675 nm and therefore had limited sensitivity in those regions. In particular, the extinction coefficients at 745, 869 and 997 nm are shown to be the most accurate, with relative accuracies and precisions close to 10 % and 15 %, respectively, while the 675 nm relative accuracy and precision are on the order of 20 %. The 510 nm extinction coefficient is shown to have limited accuracy in the SH and is only recommended for use between 20–24 km and only in the Northern Hemisphere. The V2.0 retrieval algorithm has been applied to the complete set of OMPS LP measurements, and the new dataset is publicly available.

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Classification of Tree Species as Well as Standing Dead Trees Using Triple Wavelength ALS in a Temperate Forest

Remote Sensing ◽

10.3390/rs11222614 ◽

2019 ◽

Vol 11 (22) ◽

pp. 2614 ◽

Cited By ~ 3

Author(s):

Nina Amiri ◽

Peter Krzystek ◽

Marco Heurich ◽

Andrew Skidmore

Keyword(s):

Tree Species ◽

Feature Selection Method ◽

Silver Fir ◽

Maximum Point ◽

Individual Tree ◽

Dead Trees ◽

Multi Wavelength ◽

Standing Dead ◽

Standing Dead Trees ◽

532 Nm

Knowledge about forest structures, particularly of deadwood, is fundamental for understanding, protecting, and conserving forest biodiversity. While individual tree-based approaches using single wavelength airborne laserscanning (ALS) can successfully distinguish broadleaf and coniferous trees, they still perform multiple tree species classifications with limited accuracy. Moreover, the mapping of standing dead trees is becoming increasingly important for damage calculation after pest infestation or biodiversity assessment. Recent advances in sensor technology have led to the development of new ALS systems that provide up to three different wavelengths. In this study, we present a novel method which classifies three tree species (Norway spruce, European beech, Silver fir), and dead spruce trees with crowns using full waveform ALS data acquired from three different sensors (wavelengths 532 nm, 1064 nm, 1550 nm). The ALS data were acquired in the Bavarian Forest National Park (Germany) under leaf-on conditions with a maximum point density of 200 points/m 2 . To avoid overfitting of the classifier and to find the most prominent features, we embed a forward feature selection method. We tested our classification procedure using 20 sample plots with 586 measured reference trees. Using single wavelength datasets, the highest accuracy achieved was 74% (wavelength = 1064 nm), followed by 69% (wavelength = 1550 nm) and 65% (wavelength = 532 nm). An improvement of 8–17% over single wavelength datasets was achieved when the multi wavelength data were used. Overall, the contribution of the waveform-based features to the classification accuracy was higher than that of the geometric features by approximately 10%. Our results show that the features derived from a multi wavelength ALS point cloud significantly improve the detailed mapping of tree species and standing dead trees.

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