Optical, size and mass properties of mixed type aerosols in Greece and Romania as observed by synergy of lidar and sunphotometers in combination with model simulations: A case study
Introduction
Aerosols are important constituents of the atmosphere, influencing both the air quality and the Earth's climate. They scatter and absorb solar and terrestrial radiation (direct effect) and alter the physical, optical and lifetime properties of clouds and thus the precipitation formation (indirect effect), as they act as cloud condensation nuclei (Ackermann and Chung, 1992, Seinfeld and Pandis, 1998, Lance et al., 2009, Cerully et al., 2011, Moore et al., 2013). However, the overall uncertainties in the radiative forcing effect of aerosols (anthropogenic and natural) remain still very high (Forster et al., 2007). These uncertainties can only be reduced by better quantifying the vertical and horizontal distribution of aerosols over the globe. Laser remote sensing (lidar) measurements of the vertical distribution of the aerosol optical, microphysical and mass properties can contribute to such quantification (Meloni et al., 2005, Heinold et al., 2011, Noh et al., 2012, Papayannis et al., 2012a, Kanitz et al., 2013, Reddy et al., 2013).
Aerosols belong to two categories (Pandis et al., 1995): those of natural origin (marine, volcanic, desert, biogenic, etc.) and those of anthropogenic origin (biomass burning, fossil fuel burning, etc.). However, the main sources of aerosols are mainly the large deserts, the strong volcanic eruptions and the biomass-fossil fuels burning. As a result, there is a strong spatial and temporal variation of their vertical and horizontal distribution in the troposphere (Andreae and Crutzen, 1997, Prospero et al., 2002, Balin, 2004, Abbatt et al., 2006, Tunved et al., 2006, Yu et al., 2012, Lathem et al., 2013).
Since the establishment of the European Aerosol Research Lidar Network (EARLINET) in May 2000 (Bösenberg et al., 2003, Pappalardo et al., 2004), aerosol systematic observations combining active and passive remote sensors are performed over the European continent (Pérez et al., 2004, Mona et al., 2006, Papayannis et al., 2008, Guerrero-Rascado et al., 2009, Pappalardo et al., 2010, Amiridis et al., 2013, Müller et al., 2013). In the South-Eastern (SE) European sector, systematic lidar measurements are performed in single stations in Greece, Bulgaria, Romania and recently in Cyprus, within the frame of EARLINET (Papayannis et al., 2008, Pappalardo et al., 2010, Mamouri et al., 2013, Nemuc et al., 2013, Nicolae et al., 2013).
Although the Balkan area and more specifically the Black and Aegean Seas are a cross road of several air pollutants (Lelieveld et al., 2002), no combined systematic aerosol profiling data (optical, micro-physical and mass properties) are available yet in Greece and Romania. Therefore, the level of understanding of the aerosol properties related to transport processes in SE Europe and especially over the Aegean and around the Black Sea, remains still quite low, despite some recently published data (e.g. Sciare et al., 2005, Koulouri et al., 2008, Kanakidou et al., 2011, Papayannis et al., 2012b, Theodosi et al., 2013).
To address these issues a coordinated experimental field campaign with synchronized aerosol observations was organized for the first time in Greece and Romania, at five selected stations (Fig. 1): Athens (Lat: 37.96°N, Lon: 23.78°E, 220 m above sea level (a.s.l.)), Oxylithos (Lat: 38.57°N, Lon: 24.13°E, 120 m a.s.l.), Bucharest (Lat: 44.35°N, Lon: 26.03°E, 93 m a.s.l.), Iasi (Lat: 47.17°N, Lon: 27.57°E, 200 m a.s.l.), and Timisoara (Lat: 45.73°N, Lon: 21.22°E, 102 m a.s.l.). The structure of this paper is as follows. Section 2 presents the methodology of the measurements and the models involved, while Section 3 shows the instrument description concerning the Greek and the Romanian infrastructure. Section 4 discusses a selected case study of Saharan dust particles advected and measured over the five sites, while in Section 5 we present our main conclusions.
Section snippets
Methodology
In order to investigate the vertical and spatial distribution of the aerosol optical, size and mass properties over our geographical area, related to long-range transport, an intensive campaign, called AGRO (including synergy of several instruments) was organized between 15 and 29 September 2012, simultaneously, in Greece and Romania at the aforementioned selected sites: Athens and Evia island on the Aegean Sea (Greece) and Bucharest, Iasi, and Timisoara (Romania). The AGRO campaign was
Athens site
The Athens (Greece) site belongs to the Laser Remote Sensing Unit of the National Technical University of Athens (NTUA) and is located in the Greater Athens area (Fig. 1). The NTUA lidar system (EOLE) is based on a pulsed Nd:YAG laser, emitting simultaneously at 355, 532, and 1064 nm, at 10 Hz repetition rate. The full overlap of the system is obtained at 0.5 km (at 532 nm) snd at 0.7 km (at 1064 nm) above ground, according to the detected wavelengths. A 300 mm diameter optical Cassegrainian telescope
Case study of 23–24 September 2012
Out of the total period of the AGRO campaign (15–29 September 2012), we selected to focus on the spatial distribution of the aerosol properties, in four dimensions (2 dimensional horizontal, vertical and temporal scales) during a special event of Saharan dust transported from Northern Africa over the Balkans area. This Saharan dust was captured during the AGRO campaign; starting on the night of 23 September in Athens, arriving in the early morning hours at Oxylithos and Timisoara and reaching
Conclusions
Vertical profiles of the aerosol optical, size and mass properties were studied during a 2-day case study in the frame of a coordinated experimental campaign in September 2012 based on the synergy of lidar and sunphotometers over five different sites, in Greece and Romania. Dust particles mixed with biomass burning and continental polluted ones were confined from the PBL region up to around 4–4.5 km height. High aerosol linear depolarization and lidar ratio values were measured inside the
Acknowledgements
This work was supported by grants of the Romanian National Authority for Scientific Research project no. PN 09-27 01 03, 62EU/2009 and PN-II-RU-PD-2011-3-0082 and by the European Community's FP7-INFRASTRUCTURES-2010-1 under grant no. 262254-ACTRIS and by FP7-AAT-2008-RTD-1 under grant no. 233801. The research of AP and GT has been co-financed by the European Union (European Regional Development Fund—ERDF) and the General Secretariat for Research and Technology (GSRT) of the Greek Ministry of
References (87)
- et al.
An automated method for determining the mixing layer depth from lidar observations
Atmos Environ
(1979) - et al.
An enhanced contextual fire detection algorithm for MODIS
Remote Sens Environ
(2003) - et al.
AERONET–a federated instrument network and data archive for aerosol characterization
Remote Sens Environ
(1998) - et al.
Megacities as hot spots of air pollution in the East Mediterranean
Atmos Environ
(2011) - et al.
Chemical composition and sources of fine and coarse aerosol particles in the Eastern Mediterranean
Atmos Environ
(2008) - et al.
Influence of the vertical profile of Saharan dust on the visible direct radiative forcing
J Quant Spectrosc Radiat Transf
(2005) - et al.
Estimation of radiative forcing by the dust and non-dust content in mixed East Asian pollution plumes on the basis of depolarization ratios measured with lidar
Atmos Environ
(2012) - et al.
Optical properties and vertical extension of ash layers over the Eastern Mediterranean as observed by Raman lidars during the Eyjafjallajökull eruption (May 2010)
Atmos Environ
(2012) - et al.
Summertime re-recirculations of air pollutants over the North-Eastern Iberian coast observed from systematic EARLINET lidar measurements in Barcelona
Atmos Environ
(2004) - et al.
Cloud-screening and quality control algorithms for the AERONET database
Remote Sens Environ
(2000)
Validation of the Lagrangian particle dispersion model FLEXPART against large scale tracer experiments
Atmos Environ
Solid ammonium sulfate aerosols as ice nuclei: a pathway for cirrus cloud formation
Science
Radiative effects of airborne dust and regional energy budget at the top of the atmosphere
J Appl Meteorol
Optimizing Saharan dust CALIPSO retrievals
Atmos Chem Phys
Atmospheric aerosols: biochemical sources and role in atmospheric chemistry
Science
Some remarks about lidar data preprocessing and different implementations of the gradient method for determining the aerosol layers
Ann Geophys
Combined Raman elastic-backscatter lidar for vertical profiling of moisture, aerosol extinction, backscatter, and lidar ratio
Appl Phys
Ash and fine-mode particle mass profiles from EARLINET-AERONET observations over central Europe after the eruptions of the Eyjafjallajokull volcano in 2010
J Geophys Res
Profiling of fine and coarse particle mass: case studies of Saharan dust and Eyjafjallajökull/Grimsvötn volcanic plumes
Atmos Chem Phys
Measurement and analysis of aerosols, cirrus-contrails, water vapor and temperature in the upper troposphere with the Jungfraujoch LIDAR system
Aerosol lidar intercomparison in the framework of the EARLINET project: Part II—aerosol backscatter algorithms
Appl Opt
EARLINET: A European Aerosol Research Lidar Network
Aerosol hygroscopicity and CCN activation kinetics in a boreal forest environment during the 2007 EUCAARI campaign
Atmos Chem Phys
Algorithm and software for the retrieval of vertical aerosol properties using combined lidar/radiometer data: Dissemination in EARLINET
Wavelet correlation transform method and gradient method to determine aerosol layering from lidar returns: some comments
J Atmos Oceanic Tech
Chemical composition of free tropospheric aerosol for PM1 and coarse mode at the high alpine site Jungfraujoch
Atmos Chem Phys
Automatic detection of atmospheric boundary layer height using ceilometer backscatter data assisted by a boundary layer model
Q J R Meteorol Soc
Hysplit 4 User's Guide
Variability of absorption and optical properties of key aerosol types observed in worldwide locations
J. Atmos Sci
Accuracy assessment of aerosol optical properties retrieved from AERONET sun and sky radiance measurements
J Geophys Res
Changes in atmospheric constituents and in radiative forcing
Depolarization ratio profiling at several wavelengths in pure Saharan dust during SAMUM 2006
Tellus
Optical properties of different aerosol types: seven years of combined Raman-elastic backscatter lidar measurements in Thessaloniki, Greece
Atmos Meas Tech
Extreme Saharan dust event over the southern Iberian Peninsula in September 2007: active and passive remote sensing from surface and satellite
Atmos Chem Phys
Regional modelling of Saharan dust and biomass-burning smoke
Tellus
Optical properties of aerosols and clouds: the software package OPAC
Bull Am Meteorol Soc
AERONET's version 2.0 quality assurance criteria
Proc SPIE
An alternative approach to non hydrostatic modelling
Mon Weather Rev
Radiative effect of aerosols above the northern and southern Atlantic Ocean as determined from ship-borne lidar observations
J Geophys Res
Stable analytical inversion for processing lidar returns
Appl Opt
Lidar inversion with variable backscatter extinction ratios
Appl Opt
The EOLE lidar system of the National Technical University of Athens
Optical, microphysical, mass and geometrical properties of aged volcanic particles observed over Athens, Greece, during the Eyjafjallajökull eruption in April 2010 through synergy of Raman lidar and sunphotometer measurements
Atmos Chem Phys
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