47 research outputs found
Lidar-Radiometer Inversion Code (LIRIC) for the retrieval of vertical aerosol properties from combined lidar/radiometer data: development and distribution in EARLINET
The financial support by the European Union's Horizon 2020 research and innovation programme (ACTRIS-2, grant agreement no. 654109) is gratefully acknowledged. The background of LIRIC algorithm and software was developed under the ACTRIS Research Infrastructure project, grant agreement no. 262254, within the European Union Seventh Framework Programme, which financial support is gratefully acknowledged.r I. Binietoglou received funding from the European Union's Seventh Framework Programme for research, technological development and demonstration under the grant agreement no. 289923 - ITARS.This paper presents a detailed description of
LIRIC (LIdar-Radiometer Inversion Code) algorithm for simultaneous processing of coincident lidar and radiometric
(sun photometric) observations for the retrieval of the aerosol
concentration vertical profiles. As the lidar/radiometric input data we use measurements from European Aerosol Research Lidar Network (EARLINET) lidars and collocated
sun-photometers of Aerosol Robotic Network (AERONET).
The LIRIC data processing provides sequential inversion of
the combined lidar and radiometric data. The algorithm starts
with the estimations of column-integrated aerosol parameters
from radiometric measurements followed by the retrieval of
height dependent concentrations of fine and coarse aerosols
from lidar signals using integrated column characteristics of aerosol layer as a priori constraints. The use of polarized lidar observations allows us to discriminate between spherical
and non-spherical particles of the coarse aerosol mode.
The LIRIC software package was implemented and tested
at a number of EARLINET stations. Intercomparison of the
LIRIC-based aerosol retrievals was performed for the observations by seven EARLINET lidars in Leipzig, Germany on
25 May 2009. We found close agreement between the aerosol
parameters derived from different lidars that supports high
robustness of the LIRIC algorithm. The sensitivity of the retrieval results to the possible reduction of the available observation data is also discussed.European Union (EU)
654109ACTRIS Research Infrastructure project within the European Union
262254European Union (EU)
289923 - ITAR
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EARLINET evaluation of the CATS Level 2 aerosol backscatter coefficient product
We present the evaluation activity of the European Aerosol Research Lidar Network (EARLINET) for the quantitative assessment of the Level 2 aerosol backscatter coefficient product derived by the Cloud-Aerosol Transport System (CATS) aboard the International Space Station (ISS; Rodier et al., 2015). The study employs correlative CATS and EARLINET backscatter measurements within a 50km distance between the ground station and the ISS overpass and as close in time as possible, typically with the starting time or stopping time of the EARLINET performed measurement time window within 90min of the ISS overpass, for the period from February 2015 to September 2016. The results demonstrate the good agreement of the CATS Level 2 backscatter coefficient and EARLINET. Three ISS overpasses close to the EARLINET stations of Leipzig, Germany; Ăvora, Portugal; and Dushanbe, Tajikistan, are analyzed here to demonstrate the performance of the CATS lidar system under different conditions. The results show that under cloud-free, relative homogeneous aerosol conditions, CATS is in good agreement with EARLINET, independent of daytime and nighttime conditions. CATS low negative biases are observed, partially attributed to the deficiency of lidar systems to detect tenuous aerosol layers of backscatter signal below the minimum detection thresholds; these are biases which may lead to systematic deviations and slight underestimations of the total aerosol optical depth (AOD) in climate studies. In addition, CATS misclassification of aerosol layers as clouds, and vice versa, in cases of coexistent and/or adjacent aerosol and cloud features, occasionally leads to non-representative, unrealistic, and cloud-contaminated aerosol profiles. Regarding solar illumination conditions, low negative biases in CATS backscatter coefficient profiles, of the order of 6.1%, indicate the good nighttime performance of CATS. During daytime, a reduced signal-to-noise ratio by solar background illumination prevents retrievals of weakly scattering atmospheric layers that would otherwise be detectable during nighttime, leading to higher negative biases, of the order of 22.3%. © Author(s) 2019
A methodology for investigating dust model performance using synergistic EARLINET/AERONET dust concentration retrievals
Systematic measurements of dust concentration profiles at a continental scale were recently made possible by the development of synergistic retrieval algorithms using combined lidar and sun photometer data and the establishment of robust remote-sensing networks in the framework of Aerosols, Clouds, and Trace gases Research Infra-Structure Network (ACTRIS)/European Aerosol Research Lidar Network (EARLINET). We present a methodology for using these capabilities as a tool for examining the performance of dust transport models. The methodology includes considerations for the selection of a suitable data set and appropriate metrics for the exploration of the results. The approach is demonstrated for four regional dust transport models (BSC-DREAM8b v2, NMMB/BSC-DUST, DREAM-ABOL, DREAM8-NMME-MACC) using dust observations performed at 10 ACTRIS/EARLINET stations. The observations, which include coincident multi-wavelength lidar and sun photometer measurements, were processed with the Lidar-Radiometer Inversion Code (LIRIC) to retrieve aerosol concentration profiles. The methodology proposed here shows advantages when compared to traditional evaluation techniques that utilize separately the available measurements such as separating the contribution of dust from other aerosol types on the lidar profiles and avoiding model assumptions related to the conversion of concentration fields to aerosol extinction values. When compared to LIRIC retrievals, the simulated dust vertical structures were found to be in good agreement for all models with correlation values between 0.5 and 0.7 in the 1-6 km range, where most dust is typically observed. The absolute dust concentration was typically underestimated with mean bias values of -40 to -20 mu g m(-3) at 2 km, the altitude of maximum mean concentration. The reported differences among the models found in this comparison indicate the benefit of the systematic use of the proposed approach in future dust model evaluation studies
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The unprecedented 2017â2018 stratospheric smoke event: decay phase and aerosol properties observed with the EARLINET
Six months of stratospheric aerosol observations with the European Aerosol Research Lidar Network (EARLINET) from August 2017 to January 2018 are presented. The decay phase of an unprecedented, record-breaking stratospheric perturbation caused by wildfire smoke is reported and discussed in terms of geometrical, optical, and microphysical aerosol properties. Enormous amounts of smoke were injected into the upper troposphere and lower stratosphere over fire areas in western Canada on 12 August 2017 during strong thunderstormâpyrocumulonimbus activity. The stratospheric fire plumes spread over the entire Northern Hemisphere in the following weeks and months. Twenty-eight European lidar stations from northern Norway to southern Portugal and the eastern Mediterranean monitored the strong stratospheric perturbation on a continental scale. The main smoke layer (over central, western, southern, and eastern Europe) was found at heights between 15 and 20âkm since September 2017 (about 2 weeks after entering the stratosphere). Thin layers of smoke were detected at heights of up to 22â23âkm. The stratospheric aerosol optical thickness at 532ânm decreased from values >â0.25 on 21â23 August 2017 to 0.005â0.03 until 5â10 September and was mainly 0.003â0.004 from October to December 2017 and thus was still significantly above the stratospheric background (0.001â0.002). Stratospheric particle extinction coefficients (532ânm) were as high as 50â200âMmâ1 until the beginning of September and on the order of 1âMmâ1 (0.5â5âMmâ1) from October 2017 until the end of January 2018. The corresponding layer mean particle mass concentration was on the order of 0.05â0.5â”gâmâ3 over these months. Soot particles (light-absorbing carbonaceous particles) are efficient ice-nucleating particles (INPs) at upper tropospheric (cirrus) temperatures and available to influence cirrus formation when entering the tropopause from above. We estimated INP concentrations of 50â500âLâ1 until the first days in September and afterwards 5â50âLâ1 until the end of the year 2017 in the lower stratosphere for typical cirrus formation temperatures of â55ââC and an ice supersaturation level of 1.15. The measured profiles of the particle linear depolarization ratio indicated a predominance of nonspherical smoke particles. The 532ânm depolarization ratio decreased slowly with time in the main smoke layer from values of 0.15â0.25 (AugustâSeptember) to values of 0.05â0.10 (OctoberâNovember) and <â0.05 (DecemberâJanuary). The decrease of the depolarization ratio is consistent with aging of the smoke particles, growing of a coating around the solid black carbon core (aggregates), and thus change of the shape towards a spherical form. We found ascending aerosol layer features over the most southern European stations, especially over the eastern Mediterranean at 32â35ââN, that ascended from heights of about 18â19 to 22â23âkm from the beginning of October to the beginning of December 2017 (about 2âkm per month). We discuss several transport and lifting mechanisms that may have had an impact on the found aerosol layering structures
The unprecedented 2017-2018 stratospheric smoke event : Decay phase and aerosol properties observed with the EARLINET
© Author(s) 2019. This open access work is distributed under the Creative Commons Attribution 4.0 License (https://creativecommons.org/licenses/by/4.0/).Six months of stratospheric aerosol observations with the European Aerosol Research Lidar Network (EARLINET) from August 2017 to January 2018 are presented. The decay phase of an unprecedented, record-breaking stratospheric perturbation caused by wildfire smoke is reported and discussed in terms of geometrical, optical, and microphysical aerosol properties. Enormous amounts of smoke were injected into the upper troposphere and lower stratosphere over fire areas in western Canada on 12 August 2017 during strong thunderstorm-pyrocumulonimbus activity. The stratospheric fire plumes spread over the entire Northern Hemisphere in the following weeks and months. Twenty-eight European lidar stations from northern Norway to southern Portugal and the eastern Mediterranean monitored the strong stratospheric perturbation on a continental scale. The main smoke layer (over central, western, southern, and eastern Europe) was found at heights between 15 and 20 km since September 2017 (about 2 weeks after entering the stratosphere). Thin layers of smoke were detected at heights of up to 22-23 km. The stratospheric aerosol optical thickness at 532 nm decreased from values > 0.25 on 21-23 August 2017 to 0.005-0.03 until 5-10 September and was mainly 0.003-0.004 from October to December 2017 and thus was still significantly above the stratospheric background (0.001-0.002). Stratospheric particle extinction coefficients (532 nm) were as high as 50-200 Mm-1 until the beginning of September and on the order of 1 Mm-1 (0.5- 5 Mm-1) from October 2017 until the end of January 2018. The corresponding layer mean particle mass concentration was on the order of 0.05-0.5 Όg m-3 over these months. Soot particles (light-absorbing carbonaceous particles) are efficient ice-nucleating particles (INPs) at upper tropospheric (cirrus) temperatures and available to influence cirrus formation when entering the tropopause from above. We estimated INP concentrations of 50-500 L-1 until the first days in September and afterwards 5-50 L-1 until the end of the year 2017 in the lower stratosphere for typical cirrus formation temperatures of -55 ?C and an ice supersaturation level of 1.15. The measured profiles of the particle linear depolarization ratio indicated a predominance of nonspherical smoke particles. The 532 nm depolarization ratio decreased slowly with time in the main smoke layer from values of 0.15-0.25 (August-September) to values of 0.05-0.10 (October-November) and < 0.05 (December-January). The decrease of the depolarization ratio is consistent with aging of the smoke particles, growing of a coating around the solid black carbon core (aggregates), and thus change of the shape towards a spherical form. We found ascending aerosol layer features over the most southern European stations, especially over the eastern Mediterranean at 32-35? N, that ascended from heights of about 18-19 to 22-23 km from the beginning of October to the beginning of December 2017 (about 2 km per month). We discuss several transport and lifting mechanisms that may have had an impact on the found aerosol layering structures.Peer reviewe
Tropospheric and stratospheric smoke over Europe as observed within EARLINET/ACTRIS in summer 2017
For several weeks in summer 2017, strong smoke layers were observed over Europe at numerous EARLINET
stations. EARLINET is the European research lidar network and part of ACTRIS and comprises more than 30
ground-based lidars.
The smoke layers were observed in the troposphere as well as in the stratosphere up to 25 km from Northern
Scandinavia over whole western and central Europe to the Mediterranean regions.
Backward trajectory analysis among other tools revealed that these smoke layers originated from strong wild fires
in western Canada in combination with pyrocumulus convection. An extraordinary fire event in the mid of August
caused intense smoke layers that were observed across Europe for several weeks starting on 18 August 2017.
Maximum aerosol optical depths up to 1.0 at 532 nm were observed at Leipzig, Germany, on 22 August 2017
during the peak of this event.
The stratospheric smoke layers reached extinction coefficient values of more than 600 Mmâ1 at 532 nm, a factor
of 10 higher than observed for volcanic ash after the Pinatubo eruption in the 1990s. First analyses of the intensive
optical properties revealed low particle depolarization values at 532 nm for the tropospheric smoke (spherical
particles) and rather high values (up to 20%) in the stratosphere. However, a strong wavelength dependence of
the depolarization ratio was measured for the stratospheric smoke. This indicates irregularly shaped stratospheric
smoke particles in the size range of the accumulation mode. This unique depolarization feature makes it possible
to distinguish clearly smoke aerosol from cirrus clouds or other aerosol types by polarization lidar measurements.
Particle extinction-to-backscatter ratios were rather low in the order of 40 to 50 sr at 355 nm, while values between
70-90 sr were measured at higher wavelengths.
In the western and central Mediterranean, stratospheric smoke layers were most prominent in the end of August
at heights between 16 and 20 km. In contrast, stratospheric smoke started to occur in the eastern Mediterranean
(Cyprus and Israel) in the beginning of September between 18 and 23 km. Stratospheric smoke was still visible in
the beginning of October at certain locations (e.g. Evora, Portugal), while tropospheric smoke was mainly observed
until the end of August within Europe.
An overview of the smoke layers measured at several EARLINET sites will be given. The temporal development
of these layers as well as their geometrical and optical properties will be presented
Long-term aerosol and cloud database from correlative EARLINET-CALIPSO observations
The European Aerosol Research Lidar Network,
EARLINET, performs correlative observations during
CALIPSO overpasses based on a sophisticated measurement
strategy since June 2006. Within a dedicated
activity supported by the European Space Agency
(ESA), sixteen EARLINET stations contributed about
1500 measurements during an intensive observational
period from May 2008 to October 2009. From these
measurements, we establish a long-term aerosol and
cloud database of correlative EARLINET-CALIPSO
observations. This database shall provide a basis for
homogenizing long-term space-borne observations
conducted with different lidar instruments operating
at different wavelengths on various platforms over the
next decade(s). The database is also used to study the
quality and representativeness of satellite lidar cross
sections along an orbit against long-term lidar network
observations on a continental scale.Postprint (published version
EARLINET evaluation of the CATS Level 2 aerosol backscatter coefficient product
We present the evaluation activity of the European Aerosol Research Lidar Network (EARLINET) for the quantitative assessment of the Level 2 aerosol backscatter coefficient product derived by the Cloud-Aerosol Transport
System (CATS) aboard the International Space Station (ISS; Rodier et al., 2015). The study employs correlative CATS EARLINET backscatter measurements within a 50 km
distance between the ground station and the ISS overpass
and as close in time as possible, typically with the starting
time or stopping time of the EARLINET performed asurement time window within 90 min of the ISS overpass,
for the period from February 2015 to September 2016
Integrated Precipitable Water from GPS Observations and CIMEL Sunphotometer Measurements at CGO Belsk
This paper describes results of integrated precipitable water co-located measurements from two techniques: GPS solution and CIMEL-318 sunphotometer. Integrated Precipitable Water (IPW) is an important meteorological parameter and is derived from GPS tropospheric solutions for GPS station at Central Geophysical Observatory (CGO), Polish Academy of Sciences (PAS), Belsk and compared with sunphotometer (CIMEL-318 device by Cimel Electronique) data provided by Aerosol Robotic Network (AERONET). Two dedicated and independent GPS solutions: network solution in the sub-network of European Permanent Network (EPN) and precise point positioning solution have been made to obtain tropospheric delays. The quality of dedicated tropospheric solutions has been verified by comparison with EPN tropospheric combined product. Several IPW comparisons and analyses revealed systematic difference between techniques (difference RMS is over 1 mm). IPW bias changes with season: annual close to 1 mm IPW (and semi-annual term also present). IPW bias is a function of atmospheric temperature. Probable cause of this systematic deficiency in solar photometry as IPW retrieval technique is a change of optical filter characteristics in CIMEL