P. Kokkalis

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

A coordinated experimental campaign aiming to study the aerosol optical, size and mass properties was organized in September 2012, in selected sites in Greece and Romania. It was based on the synergy of lidar and sunphotometers. In this paper we focus on a specific campaign period (23-24 September), where mixed type aerosols (Saharan dust, biomass burning and continental) were confined from the Planetary Boundary Layer (PBL) up to 4-4.5 km height. Hourly mean linear depolarization and lidar ratio values were measured inside the dust layers, ranging from 13 to 29 and from 44 to 65sr, respectively, depending on their mixing status and the corresponding air mass pathways over Greece and Romania. During this event the columnar Aerosol Optical Depth (AOD) values ranged from 0.13 to 0.26 at 532 nm. The Lidar/Radiometer Inversion Code (LIRIC) and the Polarization Lidar Photometer Networking (POLIPHON) codes were used and inter-compared with regards to the retrieved aerosol (fine and coarse spherical/spheroid) mass concentrations, showing that LIRIC generally overestimates the aerosol mass concentrations, in the case of spherical particles. For non-spherical particles the difference in the retrieved mass concentration profiles from these two codes remained smaller than ±20%. POLIPHON retrievals showed that the non-spherical particles reached concentrations of the order of 100-140 μg/m(3) over Romania compared to 50-75 μg/m(3) over Greece. Finally, the Dust Regional Atmospheric Model (DREAM) model was used to simulate the dust concentrations over the South-Eastern Europe.

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.

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.

From Hygroscopic Aerosols to Cloud Droplets: The HygrA-CD Campaign in the Athens Basin—An Overview

The international experimental campaign Hygroscopic Aerosols to Cloud Droplets (HygrA-CD), organized in the Greater Athens Area (GAA), Greece from 15 May to 22 June 2014 provided an unprecedented record of data on aerosols, clouds and meteorology. HygrA-CD brought together different active/passive remote sensing and in situ instrumentation/teams for the purpose of fostering our understanding on the physico-chemical properties of aerosols and their impact on the cloud formation in the lower troposphere, with emphasis on the top of the Planetary Boundary Layer (PBL). The use of well-established numerical weather prediction and atmospheric modeling, such as the Flexible particle (FLEXPART) dispersion model and the Weather Research and Forecasting (WRF) model enabled us to simulate air mass back-trajectories and atmospheric variables in the PBL, such as PBL height (PBLH), relative humidity, wind fields etc. This paper presents the major findings and highlights of the HygrA-CD campaign.

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.