It is widely accepted by the scientific community that our planet is experiencing a gradual climate change trend with a systematic rise in temperature, which is more pronounced during the last 50 years (Intergovernmental Panel on Climate Change – IPCC, 2018). In addition, in some regions, such as the Arctic or the Mediterranean, the degree of change in the associated processes is higher than the average increase of temperature.
There is an urgent need to intensify the research to investigate all factors that exacerbate or mitigate the effects on the earth-atmosphere energy balance. In particular, there is a limited understanding of the effect of aerosols on the characteristics and properties of clouds (indirect effect) and on their ability to absorb radiation (direct effect), an ability that changes with their ageing. These uncertainties affect both the future climate projections and the estimates of the contribution of various pollutants and other factors to the increase in global temperature and changes of other climatic parameters.
The topic of the PhD thesis is the understanding of the processes that configure, directly and indirectly the aerosols’ optical properties and feedback mechanisms on the local and regional atmospheric system of the Mediterranean. This will be accomplished with a targeted study of the optical properties of aged particles, through time series of observations in characteristic Mediterranean environments along with a comparative study of the background environment, including that of the free troposphere (ACTRIS/GAW Helmos station) and the urban background in Athens (ACTRIS/GAW Athens-Democritus station). Specific phenomena that will be examined among others are the nucleation and modelling to understand the particle condensation to cloud condensation nuclei and their direct effect in radiation transfer (scattering-absorption of radiation), including phenomena such as the wildfires in the Eastern Mediterranean and dust transport from Africa.
The study of the effect of aerosols on the climate for the above cases will be also carried out using advanced radiative transfer models. In parallel, advanced statistical models will be used to identify and extract patterns related to the study of the aerosols’ characteristics and their interaction with the climate over the Mediterranean. The complexity associated with the above interactions requires the use of both linear and non-linear models to derive properties that highlight the role of aerosols in the observed climate change the area of study.

The present Ph.D. study titled “Study on the relation of radioactive pollution and satellite observations of marine parameters and comparative analysis on a Geographic Information System”, aims at the creation of an innovative tool dedicated to the remote control of the conservative pollutants in the marine environment, by integration of in situ measurements, satellite observations and GIS for routine and emergency radiological inventory at first, but also extrapolated to other diluted pollutants too. The case study which will be investigated during this project is in the Aegean Sea, Eastern Mediterranean. Therefore, a program has been developed to explore the relations of Sea Surface Temperature, Sea Surface Salinity, Ocean Colour (OC) parameters (Chlorophyll-A concentration, Particulate Inorganic Carbon concentration, Particulate Organic Carbon concentration, Instantaneous and Daily Photosynthetically Available Radiation) and Biogeochemical parameters (Nitrates concentration, Phosphates Concentration, pH) with 137Cs activity concentrations in the Aegean Sea and analyze them to a GIS platform, as a first step for the development of this tool. SMOS, MODIS, VIIRS and CMEMS time series data are acquired processed and correlated with real time measurements of 137Cs activity concentrations from the Aegean Sea aspiring to result to a conjoint modelscheme for remote survey recording and forecasting pollutant inventory. Furthermore, additional environmental and radiological parameters and models (e.g. ecological and biological half-lives, relative biological effectiveness) will be used to the inter-relations among the study variables and biota in a GIS platform for integration to the impact level. Therefore, the innovative tool will be used for the remote detecting of: a) the inventory of radioactive pollution for a cost efficient monitoring in the marine environment to assess the radiological status, b) the impact assessment of possible radiological events and incidents, c) the estimation of the effects on the ecological pyramid (food chain) of radioactive pollution for dose estimations to both humans and ecosystems on the basis of “the one health concept” (potential capacity) whereas could be used: for the application of scenarios for forecast under accidental releases and furthermore and to investigate the application for other conservative pollutants (e.g. potential capacity heavy/trace metals). Moreover, it may be a reliable tool for support to the decision makers for early application of countermeasures in case of radiological events.

3 member supervising committee:

• Dr. G. Kitis Professor AUTH (School of Physics, Department of Nuclear and Elementary Particle Physics)
• Dr. H. Florou Collaborative Researcher NCSR”D” (Former Head of Research ERL/INRASTES/NCSR”D”)
• Dr. O. Sykioti Senior Researcher NOA (IAASARS)