R. E. Mamouri

Ground-, satellite-and simulation-based analysis of a strong dust event over Abastumani, Georgia, during May 2009

A strong dust event over Abastumani, Georgia, during May 2009 was studied using light detection and ranging (lidar), satellite and sun photometric measurements. High aerosol optical depth (AOD) values (0.45–0.57) at 500 nm were measured over the closest Aerosol Robotic Network (AERONET) site (Erdemli, Turkey), whereas over Georgia, the AOD measured by the Moderate Resolution Imaging Spectroradiometer (MODIS) was about 0.9 at 550 nm. The AERONET data analysis showed a mean aerosol effective radius of about 2.5 μm, whereas the mean value of the Ångström exponent (α) (wavelength pair 440/870 nm) was smaller than 1, indicating the dominance of large aerosols. The aerosol lidar over Abastumani showed the existence of a strong particle load from the near ground up to a height of 3.5 km. The BSC-DREAM8b forecast model showed that the dust aerosols travelled from the Saharan and the Arabic deserts to the studied area, even reaching southern Russia, covering a total distance of about 5500 km, in the height region from about 2 to 11.5 km.

An Adaptive Base Point Algorithm for the Retrieval of Aerosol Microphysical Properties

We propose a new iterative algorithm for the retrieval of the microphysical properties of stratospheric and tropospheric aerosols from multiwavelength lidar data. We consider the basic equation as an ill-posed problem and solve the system derived from spline collocation via a Pade iteration. The algorithm takes special care of the fact that the reconstruction of the distribution via spline collocation is very sensitive to the choice of base points of the chosen spline basis. The algorithm makes use of this fact by changing the base points used for the spline collocation at certain iteration steps. In addition, the effects of projection to ensure a nonnegative solution are examined. We tested how well this and other algorithms are suitable for retrieving the complex refractive index of the particles as well. We also examine whether the algorithm is capable of distinguishing between different, very small imaginary parts of the refractive index, which is often a main problem in practice. Finally, the algorithm is applied to real multiwavelength Raman lidar data and our results are partially validated by the thermodynamic chemical model Isorropia II.

EARLINET observations of the Eyjafjallajökull ash plume over Europe

EARLINET, the European Aerosol Research Lidar NETwork, established in 2000, is the first coordinated lidar network for tropospheric aerosol study on the continental scale. The network activity is based on scheduled measurements, a rigorous quality assurance program addressing both instruments and evaluation algorithms, and a standardised data exchange format. At present, the network includes 27 lidar stations distributed over Europe. EARLINET performed almost continuous measurements since 15 April 2010 in order to follow the evolution of the volcanic plume generated from the eruption of the Eyjafjallajökull volcano, providing the 4-dimensional distribution of the volcanic ash plume over Europe. During the 15-30 April period, volcanic particles were detected over Central Europe over a wide range of altitudes, from 10 km down to the local planetary boundary layer (PBL). Until 19 April, the volcanic plume transport toward South Europe was nearly completely blocked by the Alps. After 19 April volcanic particles were transported to the south and the southeast of Europe. Descending aerosol layers were typically observed all over Europe and intrusion of particles into the PBL was observed at almost each lidar site that was affected by the volcanic plume. A second event was observed over Portugal and Spain (6 May) and then over Italy on 9 May 2010. The volcanic plume was then observed again over Southern Germany on 11 May 2010.

Evaluation of CALIPSO’s Aerosol Classification Scheme During the ACEMED Experimental Campaign Over Greece: The Case Study of 9th of September 2011

In order to assess the validity of CALIPSO’s aerosol classification scheme, an experimental campaign called ACEMED (Evaluation of CALIPSO’s aerosol classification scheme over Eastern Mediterranean) has been organized over Greece on September 2011. In this study, we concentrate on the characterization of the aerosol load over Greece on 9th of September, using advanced in-situ aircraft instrumentation (onboard the FAAM-Bae146 aircraft of the UK Met Office). The analytical evaluation of CALIPSO’s aerosol-type classification scheme that is performed using synchronous/collocated satellite/airborne measurements, show a qualitatively reasonable performance of the CALIPSO’s aerosol classification scheme in the complex aerosol environment of the case under study, where smoke, continental, urban and dust aerosol components are present.

Forest Fire Aerosols: Vertically Resolved Optical and Microphysical Properties and Mass Concentration from Lidar Observations

The influence of smoke on the aerosol loading in the free troposphere from EARLINET observations are examined in this paper. Several cases during 2001–2011 were identified over Thessaloniki and Athens, Greece, when very high aerosol optical depth values in the free troposphere were observed with a UV-Raman lidar. Particle dispersion modeling (FLEXPART) and satellite hot spot fire detection (ATSR) showed that these high free tropospheric aerosol optical depths are mainly attributed to the advection of smoke plumes from biomass burning regions. The biomass burning regions were found to extend across Russia in the latitudinal belt between 45°N and 55°N, as well as in Eastern Europe. The highest frequency of agricultural fires occurred during the summer season (mainly in August). Emphasis is also given on the 2007 wild fires surrounding Athens and earlier studies performed in the frame of EARLINET. The data collected allowed the optical and microphysical characterization of the smoke aerosols that arrived over Greece, where limited information has so far been available and in synergy with AERΟNET and CALIPSO observation a first attempt is made for the vertically resolved mass concentration of the smoke plumes.

Coordinated lidar observations of Saharan dust over Europe in the frame of EARLINET-ASOS project during CALIPSO overpasses: A strong dust case study analysis with modeling support

Coordinated lidar observations of Saharan dust over Europe are performed in the frame of the EARLINET-ASOS (2006-2011) project, which comprises 25 stations: 16 Raman lidar stations, including 8 multi-wavelength (3+2 station) Raman lidar stations, are used to retrieve the aerosol microphysical properties. Since the launch of CALIOP, the two-wavelength lidar on board the CALIPSO satellite (June 2006) our lidar network has been performing correlative aerosol measurements during CALIPSO overpasses over the individual stations. In our presentation, we report on the correlative measurements obtained during Saharan dust intrusions in the period from June 2006 to June 2008. We found that the number of dust events is generally greatest in late spring, summer and early autumn periods, mainly in southern and south-eastern Europe. A measurement example is presented that was analyzed to show the potential of a ground based lidar network to follow a dust event over a specific study area, in correlation with the CALIOP measurements. The dust transport over the studied area was simulated by the DREAM forecast model. Cross-section analyses of CALIOP over the study area were used to assess the model performance for describing and forecasting the vertical and horizontal distribution of the dust field over the Mediterranean. Our preliminary results can be used to reveal the importance of the synergy between the CALIOP measurement and the dust model, assisted by ground-based lidars, for clarifying the overall transport of dust over the European continent.