Elias Mavromatidis

Heterogeneous Chemical Processes and Their Role on Particulate Matter Formation in the Mediterranean Region

The impact of particulate matter on air quality and the environment is an important subject for areas like the Greater Mediterranean Region, mostly due to the coexistence of major anthropogenic and natural sources. Such coexistence can create air quality conditions that exceed the imposed air quality limit values. Particulate matter formation and the factors enhancing or reducing such formation in the Mediterranean Region will be the primary focus of the work presented herein. Natural particulate matter appears mainly in the form of desert dust, sea salt and pollen among others and anthropogenic particulate matter appears as particulate sulfate and nitrate. The processes affecting the formation of new types of aerosols are based on the heterogeneous uptake of gases onto dust particles. New model development will be presented referring to the implementation of sea salt production and heterogeneous chemical processes leading to new aerosol formation in the photochemical model CAMx. Results from these simulations showed reasonable agreement with the available measurements. These results also revealed interesting effects of the coexistence of natural and anthropogenic particulate matter concerning the direct and indirect impacts on air quality and the environment.

Ten-year operational dust forecasting – Recent model development and future plans

The Sahara desert is one of the major sources of mineral dust on Earth, producing up to 2x108 t yr-1. A combined effort has been devoted during the last ten years at the University of Athens (UOA) from the Atmospheric Modeling and Weather Forecasting Group (AM&WFG) to the development of an analysis and forecasting tool that will provide early warning of Saharan dust outbreaks. The developed tool is the SKIRON limited-area forecasting system, based on the Eta limited area modeling system with embedded algorithms describing the dust cycle. A new version of the model is currently available, with extra features like eight-size particle bins, radiative transfer corrections, new dust source identification and utilization of rocky soil characterization and incorporation of more accurate deposition schemes. The new version of SKIRON modeling system is coupled with the photochemical model CAMx in order to study processes like the shading effect of dust particles on photochemical processes and the production of second and third generation of aerosols. Moreover, another new development in the AM&WFG is based on the RAMS model, with the incorporation of processes like dust and sea-salt production, gas and aqueous phase chemistry and particle formation. In this study, the major characteristics of the developed (and under development) modeling systems are presented, as well as the spatiotemporal distribution of the transported dust amounts, the interaction with anthropogenically-produced particles and the potential implications on radiative transfer.

A case of nighttime high ozone concentration over the greater Athens area

A cas e of abrupt and significant increase of surface ozone was examined, which is recorded during the night of October 9 th , 2003, over the area of the Thriassion Plain – Greece, being acco mpanied by the occurrence of a wind outbreak during the same period. As this increase cannot be explained by the ordinary diurnal evolution of tropospheric ozone concentration, the possibility of downward stratospheric ozone transport was investigated. It was indeed found that the case is associated with tropopause folding and subsequent stratospheric air intrusion in the upper troposphere over Greece. With the aid of mesoscale modeling, being also supported by the hydraulic theory, it was found that the intense wind outbreak is associated with the development of disturbances in the lee side of the neighbouring mountain ranges. These disturbances contribute to the free troposphere – atmospheric boundary layer interaction, facilitating the transportation of stratospheric air close to the surface, thus resulting to the observed tropospheric ozone increase. Zusammenfassung

Forest Fire Modeling and the Effect of Fire-Weather in Landscape Fire Behavior for the Region of Attica, Greece

The knowledge of meteorological conditions is critical for the description of fire weather. In this paper, the mesoscale numerical meteorological model RAMS has been used to simulate the surface wind and temperature in two fire events in the region of Attica in Greece. The FARSITE (Fire Area Simulator) fire model, for the description of forest fire behavior, taking into consideration the influence of fuels, topography and weather conditions. The accuracy of the results was evaluated and confirmed that the use of suitable fuel models is very important for achieving reliable simulations for the devastating fires.

Seasonal Forecasts for the 2010 Russian Heat Wave Using an Atmospheric General Circulation Model

In this study the capabilities of a state-of-the-art Atmospheric General Circulation Model (AGCM) for the estimation of the atmospheric conditions on seasonal scale are examined. Seasonal simulations were carried out using the NCAR Community Atmosphere Model (CAM 3). The unusual weather patterns prevailed over Europe and Asia during July and August of 2010, which led in the development of the Russian heat wave and provoked severe rainfall in Pakistan, were simulated by using an ensemble based methodology. The ensemble was consisting of 61 independent members and it has been produced by consecutive simulations performed for each day of January and April 2010. Each hindcast has been integrated for 8 and 5 months ahead. The model outputs have been statistically processed in order to estimate the monthly average temperature anomalies and the monthly accumulated precipitation probability of exceedance. Preliminary results suggest that the system is able to reproduce the large scales of the atmospheric circulation indicating that it can be a useful tool for better understanding the mechanisms of atmospheric variations on seasonal scale.