27 research outputs found
Contribution of EARLINET/ACTRIS to the summer 2013 Special Observing Period of the ChArMEx project: monitoring of a Saharan dust event over the western and central Mediterranean
In the framework of the Chemistry-Aerosol Mediterranean
Experiment (ChArMEx; http://charmex.lsce.ipsl.fr/) initiative, a
field campaign took place in the western Mediterranean Basin
between 10 June and 5 July 2013 within the ADRIMED (Aerosol
Direct Radiative Impact on the regional climate in the
MEDiterranean region) project. The scientific objectives of
ADRIMED are the characterization of the most common
‘Mediterranean aerosols’ and their direct radiative forcing (column
closure and regional scale). During 15–24 June a multiintrusion
dust event took place over the western and central
Mediterranean Basin. Extra measurements were carried out by
some EARLINET/ACTRIS (European Aerosol Research Lidar
Network /Aerosols, Clouds, and Trace gases Research
InfraStructure Network, http://www.actris.net/) lidar stations in
Spain and Italy, in particular on 22 June in support to the flight
over southern Italy of the Falcon 20 aircraft involved in the
campaign. This article describes the physical and optical properties
of dust observed at the different lidar stations in terms ofdust plume centre of mass, optical depth, lidar ratio, and particle
depolarization ratio. To link the differences found in the
origin of dust plumes, the results are discussed on the basis
of back-trajectories and air- and space-borne lidars. This work
puts forward the collaboration between a European research
infrastructure (ACTRIS) and an international project (ChArMEx)
on topics of interest for both parties, and more generally for the
atmospheric community.Published4698-47114A. Clima e OceaniJCR Journalrestricte
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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 InfraStructure 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, DREAMABOL, 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 μg 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
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
TARJETA DE VISITA [Material gráfico]
EUROPACopia digital. Madrid : Ministerio de Educación, Cultura y Deporte, 201
Methodologies to obtain aerosol property profiles from three-wavelength elastic lidar signals
The Lidar/Radiometer Inversion Code (LIRIC) and the Constrained Iterative Inversion (CII) procedure combined with a graphical aerosol classification framework (GF) have been used to analyse their ability in characterizing the altitude dependence of aerosol properties and evaluate their benefits and weaknesses. LIRIC and the CII technique rely on elastic lidar signals at 355, 532, and 1064 nm and collocated Aerosol Robotic Network (AERONET) Sun/sky photometer measurements to retrieve aerosol parameter profiles at the lidar wavelengths. The aerosol GF relies on the combined analysis of the Ångström exponent at the wavelength pairs 355 and 1064 nm (A(355, 1064)) and its spectral curvature (ΔA = A(355, 532) – A(532, 1064)) to estimate the fine-modal radius and the 532 nm fine-mode fraction. The application of the LIRIC and CII-GF techniques to three selected case studies representative of Central Mediterranean aerosol scenarios has revealed that the differences between the aerosol products from LIRIC and the corresponding ones from the CII-GF procedure varied with altitude, increased with the lidar wavelength decrease, and were significantly large when aerosol from different sources and/or from different advection routes was located at the altitudes sounded by the lidar. The plot on the aerosol GF of A(355, 1064) versus the spectral curvature has indicated that the LIRIC constraint that the fine-modal radius is height independent may represent a weakness if aerosol types and hence aerosol size distributions vary with altitude. The use of lidar ratios (LRs) constant with altitude could represent one of the main weaknesses of the CII-GF technique. The combined use of both techniques should allow obtaining a better characterization of the altitude dependence of aerosol properties from three-wavelength elastic lidar signals
Mediterranean aerosol typing by integrating three-wavelength lidar and sun photometer measurements
Backscatter lidar measurements at 355, 532, and 1064 nm combined with aerosol optical thicknesses (AOTs) from sun photometer measurements collocated in space and time were used to retrieve the vertical profiles of intensive and extensive aerosol parameters. Then, the vertical profiles of the Ångström coefficients for different wavelength pairs (Å(λ1, λ2, z)), the color ratio (CR(z)), the fine mode fraction (η(z)) at 532 nm, and the fine modal radius (R f (z)), which represent aerosol characteristic properties independent from the aerosol load, were used for typing the aerosol over the Central Mediterranean. The ability of the Ångström coefficients to identify the main aerosol types affecting the Central Mediterranean with the support of the backward trajectory analysis was first demonstrated. Three main aerosol types, which were designed as continental-polluted (CP), marine-polluted (MP), and desert-polluted (DP), were identified. We found that both the variability range and the vertical profile structure of the tested aerosol intensive parameters varied with the aerosol type. The variability range and the altitude dependence of the aerosol extinction coefficients at 355, 532, and 1064 nm, respectively, also varied with the identified aerosol types even if they are extensive aerosol parameters. DP, MP, and CP aerosols were characterized by the Å(532, 1064 nm) mean values ± 1 standard deviation equal to 0.5 ± 0.2, 1.1 ± 0.2, 1.6 ± 0.2, respectively. η(%) mean values ± 1SD were equal to 50 ± 10, 73 ± 7, and 86 ± 6 for DP, MP, and CP aerosols, respectively. The R f and CR mean values ± 1SD were equal to 0.16 ± 0.05 μm and 1.3 ± 0.3, respectively, for DP aerosols; to 0.12 ± 0.03 μm and 1.8 ± 0.4, respectively, for MP aerosols; and to 0.11 ± 0.02 μm and 1.7 ± 0.4, respectively, for CP aerosols. CP and DP aerosols were on average responsible for greater AOT and LR values, but the LR and AOT dependence on wavelength was stronger for CP than for DP aerosols. The plots of the lidar ratio values at 355 nm versus the mean columnar values of the 532-1064 nm Ångström coefficient (Å c), the fine mode radius, the fine mode fraction at 532 nm (η c), and the color ratio, respectively, furthermore revealed the greater ability of the Å c and η c values to characterize different aerosol types
Profiling of fine- and coarse-mode particles with LIRIC (LIdar/Radiometer Inversion Code)
The paper investigates numerical procedures that allow determining the dependence
on altitude of aerosol properties from multi wavelength elastic lidar signals. In particular,
the potential of the LIdar/Radiometer Inversion Code (LIRIC) to retrieve the ver-
5 tical profiles of fine and coarse-mode particles by combining 3-wavelength lidar measurements
and collocated AERONET (AErosol RObotic NETwork) sun/sky photometer
measurements is investigated