Seventeen-year systematic measurements of dust aerosol optical properties using the eole ntua lidar system (2000-2016)

A comprehensive analysis of the seasonal variability of the optical properties of Saharan dust aerosols over Athens, Greece, is presented for a 17-year time period (2000-2016), as derived from multi-wavelength Raman lidar measurements (57 dust events with more than 80 hours of measurements). The profiles of the derived aerosol optical properties (aerosol backscatter and extinction coefficients, lidar ratio and aerosol Ångström exponent) at 355 nm are presented. For these dust events we found a mean value of the lidar ratio of ~52±13 sr at 355 nm and of ~58±8 sr (not shown) at 532 nm (2-4 km a.s.l. height). For our statistical analysis, presented here, we used monthly-mean values and time periods under cloud-free conditions. The number of dust events was greatest in late spring, summer, and early autumn periods. In this paper we also present a selected case study (04 April 2016) of desert dust long-range transport from the Saharan desert.

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Systematic lidar observations of Saharan dust layers over Athens, Greece in the frame of EARLINET project (2004–2006)

Annales Geophysicae ◽

10.5194/angeo-27-3611-2009 ◽

2009 ◽

Vol 27 (9) ◽

pp. 3611-3620 ◽

Cited By ~ 35

Author(s):

A. Papayannis ◽

R. E. Mamouri ◽

V. Amiridis ◽

S. Kazadzis ◽

C. Pérez ◽

...

Keyword(s):

Center Of Mass ◽

Mean Value ◽

Saharan Dust ◽

Dust Layer ◽

Lidar Measurements ◽

Multi Wavelength ◽

Moderate Resolution ◽

Moderate Resolution Imaging Spectroradiometer ◽

Dust Events ◽

Aerosol Dust

Abstract. In this paper we present a statistical analysis on the geometrical and optical properties of Saharan dust layers observed over Athens, Greece, in a three-year period from 1 January 2004 up to 31 December 2006. The observations of the vertical aerosol profile were performed by the multi-wavelength (355-532-1064-387-607 nm) Raman lidar system of the National Technical University of Athens (NTUA) operated in the city of Athens (37°98' N, 23°77' E), Greece, in the frame of the European Aerosol Research Lidar Network (EARLINET-ASOS) project. The number of dust events was greatest in late spring, summer, and early autumn periods. This was evident also by aerosol observations during dust outbreaks obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS). In our lidar measurements, multiple aerosol dust layers of variable thickness (680–4800 m) were observed. The center of mass of these layers was located in altitudes between 1600 and 5800 m. However, the mean thickness of the dust layer typically stayed around 2700 m and the corresponding mean center of mass was of the order of 2900 m. The top of the dust layer ranged from 2000 to 8000 m, with a mean value of the order of 4700 m. MODIS observations during dust outbreaks showed that the AOD values at 550 nm ranged between 0.3–0.6, while the corresponding Angström exponent (AE) values were of the order of 0.5–0.65, indicating the presence of rather large particles.

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Detection of Saharan dust and biomass burning events using near real-time intensive aerosol optical properties in the northwestern Mediterranean

10.5194/acp-2015-902 ◽

2016 ◽

Author(s):

M. Ealo ◽

A. Alastuey ◽

A. Ripoll ◽

N. Pérez ◽

M. C. Minguillón ◽

...

Keyword(s):

Optical Properties ◽

Biomass Burning ◽

Mineral Dust ◽

Organic Aerosol ◽

Saharan Dust ◽

Aerosol Optical Properties ◽

Angstrom Exponent ◽

Ångström Exponent ◽

Dust Events ◽

Ångstrom Exponent

Abstract. The study of Saharan dust events (SDE) and biomass burning (BB) emissions are both topic of great scientific interest since they are frequent and important polluting scenarios affecting air quality and climate. The main aim of this work is evaluating the feasibility of using near real-time in situ aerosol optical measurements for the detection of these atmospheric events in the Western Mediterranean Basin (WMB). With this aim, intensive aerosol optical properties (SAE: scattering Ångström exponent, AAE: absorption Ångström exponent, SSAAE: single scattering albedo Ångström exponent, and g: asymmetry parameter) were derived from multi-wavelength aerosol light scattering, hemispheric backscattering and absorption measurements performed at regional (Montseny; MSY, 720 m a.s.l.) and continental (Montsec; MSA, 1570 m a.s.l.) background sites in the WMB. A sensitivity study aiming at calibrating the measured intensive optical properties for SDE and BB detection is presented and discussed. The detection of Saharan dust events (SDE) by means of the SSAAE parameter and Ångström matrix depended on the altitude of the measurement station, and on SDE intensity. At MSA (mountain-top site) SSAAE detected around 85% of SDE compared with 50% at MSY station, where pollution episodes dominated by fine anthropogenic particles frequently masked the effect of mineral dust on optical properties during less intense SDE. Furthermore, an interesting feature of SSAAE was its capability to detect the presence of mineral dust after the end of SDE. Thus, resuspension processes driven by summer regional atmospheric circulations and dry conditions after SDE favored the accumulation of mineral dust at regional level having important consequences for air quality. On average, SAE, AAE and g ranged between -0.7 and 1, 1.3 and 2.5, and 0.5 and 0.75, respectively, during SDE. Based on the Aethalometer model, biomass burning (BB) contribution to equivalent black carbon (BC) accounted for 36% and 40% at MSY and MSA respectively. Linear relationships were found between AAE and %BCbb, with AAE values reaching around 1.5 when %BCbb was higher than 50%. BB contribution to organic matter (OM) at MSY was around 30%. Thus FF combustion sources showed important contributions to both BC and OM in the region under study. Results for OM source apportionment showed good agreement with simultaneous biomass burning organic aerosol (BBOA) and hydrocarbon-like organic aerosol (HOA) calculated from Positive Matrix Factorization (PMF) applied to simultaneous Aerosol Mass Spectrometer (ACSM) measurements. A wildfire episode was identified at MSY, showing AAE values up to 2 when daily BB contributions to BC and OM were 73% and 78% respectively.

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Seasonal variability of aerosol optical properties observed by means of a Raman lidar at an EARLINET site over Northeastern Spain

Atmospheric Chemistry and Physics ◽

10.5194/acp-11-175-2011 ◽

2011 ◽

Vol 11 (1) ◽

pp. 175-190 ◽

Cited By ~ 47

Author(s):

M. Sicard ◽

F. Rocadenbosch ◽

M. N. M. Reba ◽

A. Comerón ◽

S. Tomás ◽

...

Keyword(s):

Boundary Layer ◽

Optical Properties ◽

Planetary Boundary Layer ◽

Optical Thickness ◽

Seasonal Variability ◽

Aerosol Optical Thickness ◽

Saharan Dust ◽

Raman Lidar ◽

Aerosol Optical Properties ◽

Lidar Ratio

Abstract. The annual and seasonal variability of aerosol optical properties observed by means of a Raman lidar over Northeastern Spain has been assessed. The lidar representativeness has first been checked against sun-photometer measurements in terms of aerosol optical thickness. Then the annual cycle and the seasonal variability of the planetary boundary layer aerosol optical thickness and its fraction compared to the columnar optical thickness, the lidar ratio, the backscatter-related Ångström exponent and the planetary boundary layer height are analyzed and discussed. Winter and summer mean profiles of extinction, backscatter and lidar ratio retrieved with the Raman algorithm are presented. The analysis shows the impact of most of the natural events (Saharan dust intrusions, wildfires, etc.) and meteorological situations (summer anticyclonic situation, the formation of the Iberian thermal low, winter long-range transport from North Europe and/or North America, re-circulation flows, etc.) occurring in the Barcelona area. A detailed study of a special event including a combined intrusion of Saharan dust and biomass-burning particles proves the suitability of combining the retrieval of aerosol optical properties from Raman and pure elastic lidar measurements to discriminate spatially different types of aerosols and to follow their spatial and temporal evolution.

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Measurements of Saharan dust aerosols over the Eastern Mediterranean using elastic backscatter-Raman lidar, spectrophotometric and satellite observations in the frame of the EARLINET project

Atmospheric Chemistry and Physics ◽

10.5194/acp-5-2065-2005 ◽

2005 ◽

Vol 5 (8) ◽

pp. 2065-2079 ◽

Cited By ~ 140

Author(s):

A. Papayannis ◽

D. Balis ◽

V. Amiridis ◽

G. Chourdakis ◽

G. Tsaknakis ◽

...

Keyword(s):

Eastern Mediterranean ◽

Mean Value ◽

Saharan Dust ◽

Back Trajectory ◽

Air Mass ◽

Mean Values ◽

Dust Aerosols ◽

Back Trajectory Analysis ◽

Spectrophotometric Data ◽

Lidar Ratio

Abstract. We report on the vertical distributions of Saharan dust aerosols over the N.E. Mediterranean region, which were obtained during a typical dust outbreak on August 2000, by two lidar systems located in Athens and Thessaloniki, Greece, in the frame of the European EARLINET project. MODIS and ground sun spectrophotometric data, as well as air-mass backward trajectories confirmed the existence of Saharan dust in the case examined, which was also successfully forecasted by the DREAM dust model. The lidar data analysis for the period 2000-2002 made possible, for the first time, an estimation of the vertical extent of free tropospheric dust layers [mean values of the aerosol backscatter and extinction coefficients and the extinction-to-backscatter ratio (lidar ratio, LR) at 355 nm], as well as a seasonal distribution of Saharan dust outbreaks over Greece, under cloud-free conditions. A mean value of the lidar ratio at 355 nm was obtained over Athens (53±1 sr) and over Thessaloniki (44±2 sr) during the Saharan dust outbreaks. The corresponding aerosol optical thickness (AOT) at 355 nm, in the altitude range 0-5 km, was 0.69±0.12 and 0.65±0.10 for Athens and Thessaloniki, respectively (within the dust layer the AOT was 0.23 and 0.21, respectively). Air-mass back-trajectory analysis performed in the period 2000-2002 for all Saharan dust outbreaks over the N.E. Mediterranean indicated the main pathways followed by the dust aerosols.

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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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Multi-wavelength Raman lidar observations of the Eyjafjallajökull volcanic cloud over Potenza, Southern Italy

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-11-12763-2011 ◽

2011 ◽

Vol 11 (4) ◽

pp. 12763-12803 ◽

Cited By ~ 12

Author(s):

L. Mona ◽

A. Amodeo ◽

G. D'Amico ◽

A. Giunta ◽

F. Madonna ◽

...

Keyword(s):

Southern Italy ◽

Saharan Dust ◽

Depolarization Ratio ◽

Raman Lidar ◽

Lidar Measurements ◽

Ångström Exponent ◽

Multi Wavelength ◽

Lidar Ratio ◽

Linear Depolarization Ratio ◽

532 Nm

Abstract. Multi-wavelength Raman lidar measurements were performed at CNR-IMAA Atmospheric Observatory (CIAO) during the entire Eyjafjallajökull explosive eruptive period in April–May 2010, whenever weather conditions permitted. A methodology for volcanic layer identification and accurate aerosol typing has been developed on the basis both of the multi-wavelength Raman lidar measurements and EARLINET measurements performed at CIAO since 2000. The aerosol mask for lidar measurements performed at CIAO during the 2010 Eyjafjallajökull eruption has been obtained. Volcanic aerosol layers have been observed in different periods: 19–22 April, 27–29 April, 8–9 May, 13–14 May and 18–19 May. A maximum aerosol optical depth of about 0.12–0.13 was observed on 20 April, 22:00 UTC and 13 May, 20:30 UTC. Volcanic particles have been detected both at low altitudes, in the free troposphere and in the upper troposphere. Intrusions into the PBL have been revealed on 21–22 April and 13 May. In the April–May period Saharan dust intrusions typically occur in Southern Italy. For the period under investigations, a Saharan dust intrusion was observed on 13–14 May: dust and volcanic particles have been simultaneously observed at CIAO both at separated different levels and mixed within the same layer. Lidar ratios at 355 and 532 nm, Ångström exponent at 355/532 nm, backscatter related Ångström exponent at 532/1064 nm and particle linear depolarization ratio at 532 nm measured inside the detected volcanic layers have been discussed. The dependence of these quantities on relative humidity (RH) has been investigated by using co-located microwave profiler measurements. The particle linear depolarization ratio increasing with RH, lidar ratio values at 355 nm around 80 sr, and values of the ratio of lidar ratios greater than 1 suggest the presence of sulfates mixed with continental aerosol. Lower lidar ratio values (around 40 sr) increasing with RH and values of the ratio of lidar ratios lower than 1 indicate the presence of some aged ash inside these sulfate layers.

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Seasonal variability of aerosol optical properties observed by means of an elastic-Raman lidar over Northeastern Spain

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-10-14053-2010 ◽

2010 ◽

Vol 10 (6) ◽

pp. 14053-14094

Author(s):

M. Sicard ◽

M. N. M. Reba ◽

F. Rocadenbosch ◽

A. Comerón ◽

S. Tomás ◽

...

Keyword(s):

Boundary Layer ◽

Optical Properties ◽

Planetary Boundary Layer ◽

Optical Thickness ◽

Seasonal Variability ◽

Aerosol Optical Thickness ◽

Saharan Dust ◽

Raman Lidar ◽

Aerosol Optical Properties ◽

Lidar Ratio

Abstract. The annual and seasonal variability of aerosol optical properties observed by means of an elastic-Raman lidar over Northeastern Spain has been assessed. The lidar representativeness has first been checked against sun-photometer measurements in terms of aerosol optical thickness. Then the annual cycle and the seasonal variability of the planetary boundary layer aerosol optical thickness and its fraction compared to the columnar optical thickness, the lidar ratio, the backscatter-related Ångström exponent and the planetary boundary layer height have been analyzed and discussed. Winter and summer mean profiles of extinction, backscatter and lidar ratio retrieved with the Raman algorithm have been presented. The analysis shows the impact of most of the natural events (Saharan dust intrusions, wildfires, etc.) and meteorological situations (summer anticyclonic situation, the formation of the Iberian thermal low, winter long-range transport from North Europe and/or North America, re-circulation flows, etc.) occurring in the Barcelona area. A detail study of a special event including a combined intrusion of Saharan dust and biomass-burning particles has proven the suitability of combining nighttime Raman- and daytime pure elastic-inversions to discriminate spatially different types of aerosols and to follow their spatial and temporal evolution.

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Measurements of Saharan dust aerosols over the Eastern Mediterranean using elastic backscatter-Raman lidar, spectrophotometric and satellite observations in the frame of the EARLINET project

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-5-2075-2005 ◽

2005 ◽

Vol 5 (2) ◽

pp. 2075-2110 ◽

Cited By ~ 4

Author(s):

A. Papayannis ◽

D. Balis ◽

V. Amiridis ◽

G. Chourdakis ◽

G. Tsaknakis ◽

...

Keyword(s):

Eastern Mediterranean ◽

Mean Value ◽

Saharan Dust ◽

Back Trajectory ◽

Air Mass ◽

Mean Values ◽

Dust Aerosols ◽

Back Trajectory Analysis ◽

Spectrophotometric Data ◽

Lidar Ratio

Abstract. We report on the vertical distributions of Saharan dust aerosols over the N.E. Mediterranean region, which were obtained during a typical dust outbreak on August 2000, by two lidar systems located in Athens and Thessaloniki, Greece, in the frame of the European EARLINET project. MODIS and ground sun spectrophotometric data, as well as air-mass backward trajectories confirmed the existence of Saharan dust in the case examined, which was also successfully forecasted by the DREAM dust model. The lidar data analysis for the period 2000–2002 made possible, for the first time, an estimation of the vertical extent of free tropospheric dust layers (mean values of the aerosol backscatter and extinction coefficients and the extinction-to-backscatter ratio (lidar ratio, LR) at 355 nm), as well as a seasonal distribution of Saharan dust outbreaks over Greece, under cloud-free conditions. A mean value of the lidar ratio at 355 nm was obtained over Athens (52.81±1.02 sr) and over Thessaloniki (44.19±1.72 sr) during the Saharan dust outbreaks. The corresponding aerosol optical thickness (AOT) at 355 nm, in the altitude range 0–5 km, was 0.69±0.12 and 0.65±0.10 for Athens and Thessaloniki, respectively (within the dust layer the AOT was 0.23 and 0.21, respectively). Air-mass back-trajectory analysis performed in the period 2000–2002 for all Saharan dust outbreaks over the N. E. Mediterranean indicated the main pathways followed by the dust aerosols.

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EARLINET dust observations vs. BSC-DREAM8b modeled profiles: 12-year-long systematic comparison at Potenza, Italy

Atmospheric Chemistry and Physics ◽

10.5194/acp-14-8781-2014 ◽

2014 ◽

Vol 14 (16) ◽

pp. 8781-8793 ◽

Cited By ~ 39

Author(s):

L. Mona ◽

N. Papagiannopoulos ◽

S. Basart ◽

J. Baldasano ◽

I. Binietoglou ◽

...

Keyword(s):

Center Of Mass ◽

Saharan Dust ◽

Raman Lidar ◽

Dust Layer ◽

Systematic Comparison ◽

Dust Extinction ◽

Lidar Measurements ◽

Order Of Magnitude ◽

Lidar Ratio ◽

532 Nm

Abstract. In this paper, we report the first systematic comparison of 12-year modeled dust extinction profiles vs. Raman lidar measurements. We use the BSC-DREAM8b model, one of the most widely used dust regional models in the Mediterranean, and Potenza EARLINET lidar profiles for Saharan dust cases, the largest one-site database of dust extinction profiles. A total of 310 dust cases were compared for the May 2000–July 2012 period. The model reconstructs the measured layers well: profiles are correlated within 5% of significance for 60% of the cases and the dust layer center of mass as measured by lidar and modeled by BSC-DREAM8b differ on average 0.3 ± 1.0 km. Events with a dust optical depth lower than 0.1 account for 70% of uncorrelated profiles. Although there is good agreement in terms of profile shape and the order of magnitude of extinction values, the model overestimates the occurrence of dust layer top above 10 km. Comparison with extinction profiles measured by the Raman lidar shows that BSC-DREAM8b typically underestimates the dust extinction coefficient, in particular below 3 km. Lowest model–observation differences (below 17%) correspond to a lidar ratio at 532 nm and Ångström exponent at 355/532 nm of 60 ± 13 and 0.1 ± 0.6 sr, respectively. These are in agreement with values typically observed and modeled for pure desert dust. However, the highest differences (higher than 85%) are typically related to greater Ångström values (0.5 ± 0.6), denoting smaller particles. All these aspects indicate that the level of agreement decreases with an increase in mixing/modification processes.

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