M. Varinou

Some observational and modeling evidence of long-range transport of air pollutants from Europe toward the Israeli coast

The present paper reports results of a study that attempted to elucidate the factors causing relatively high levels of particulate sulfate that have frequently been observed over central Israel. Aircraft research flights were performed some 70 km west of and parallel to the Israeli coastline during September 1993 and June 1994. Comparison between the two measurement periods revealed a distinctive difference between the two different sampled air masses. While both air masses were nearly homogeneous throughout the measurement period and along the 180 km flight path, the air mass sampled in September 1993 was much cleaner than the air mass sampled during June 1994. The concentrations of the air pollutants measured during the 1993 campaign averaged 0.7 ± 0.4 parts per billion by volume (ppbv) SO 2 , 1.0 ± 0.6 ppbv NO y , 39 ± 7 ppbv O 3 and 38 ± 7 nmol/m 3 particulate sulfate, whereas in the second period the levels averaged 3.0 ± 1.0, 3.9 ± 1.8, 48 ± 9, and 108 ± 63, respectively. These results suggest that the two air masses traveled different paths before reaching the eastern Mediterranean region. Further examination of the air mass sources and transport were performed using the Regional Atmospheric Modeling System for meteorological simulations and the Hybrid Particle and Concentration Transport Package for dispersion modeling. The model simulation showed that during the 1993 measurement period, the pollution sources in southern Europe and the Balkans did not effect the eastern coasts of the Mediterranean, while the synoptic conditions and simulation results for the June 1994 period indicated that the winds over the eastern Mediterranean tended to be northwesterly and thus forcing the polluted air masses toward the coast of Israel.

Numerical Simulations of the Meteorological and Dispersion Conditions during an Air Pollution Episode over Athens, Greece

In this study a summer air pollution episode from 6 to 8 August 1994 over Athens, Greece, is investigated through advanced atmospheric modeling. This episode was reported from the air quality monitoring network, as well as from research aircraft measurements performed during this period for the Transport and Transformation of Air Pollutants from Europe to the East Mediterranean region project. The meteorological conditions prevailing during the period 6‐8 July 1994 are analyzed based on simulations performed with the Colorado State University‐ Regional Atmospheric Modeling System and on the available surface and upper-air observations. Indeed, the synoptic settings induced favorable conditions for the development of local-scale circulations, which defined the poor dispersion conditions over the area. The dispersion of the urban plume of Athens is studied with the use of the Hybrid Particle and Concentration Transport package model. The urban plume of Athens is tracked down the Saronic Gulf and the eastern coast of Peloponnisos, more than 200 km southward from the Athens Basin in good agreement with the research aircraft observations.

Observational evidence of an ozone episode over the Greater Athens Area

Research flights have been performed over the Greater Athens Area (GAA) and southwards over the Island of Aegina and east of Peloponnisos in order to investigate the evolution of an ozone episode over GAA and the transportation of the urban pollution plume southwards from the Athens region. During the 3 day period of 6 July to 8 July 1994, the GAA was under the influence of an ozone episode with ground-level noontime concentrations of more than 120 ppbv. Upper-air ozone concentrations measured during the flights were as high as 135 ppbv. The interaction of the weak synoptic conditions over the area along with the development of a mesoscale thermal circulation created poor dispersion conditions during the period of interest and resulted in elevated ozone levels. The primary pollutants emitted in the GAA during the night and early morning hours, were funneled out to the Saronic Gulf and southwards along the southwestern Aegean Sea, near the coast of east Peloponnisos. Under the influence of strong sunlight these primary pollutants continued to undergo photochemical reaction giving rise to elevated ozone levels tens of kilometers downwind of the pollution emission sources. Further evidence of the photochemically-aged air masses was the high correlation (R2 = 0.8) observed between NOy, and ozone. The ozone production efficiency in these transported air masses reached a value of close to six.

The role of anthropogenic and biogenic emissions on tropospheric ozone formation over greece

Abstract In the frame of this work, the sensitivity of a grid-based photochemical model on the emission inventory is examined. More precisely, the role of various emission categories on simulated oxidant formation is investigated and especially the biogenic ones. Special emphasis is given on the investigation of the role of the biogenic emissions on tropospheric ozone formation over areas with significant anthropogenic sources. The area of interest is the SE part of the Greek Peninsula where there are various types of anthropogenic pollutant sources and important biogenic sources from forest areas. Ozone air quality simulations were performed using the combined system of the atmospheric model RAMS and the photochemical model UAM. The simulations revealed that there is a significant increase of the calculated ozone concentrations over areas with significant precursor sources when biogenic emissions are taken into account. This increase is more pronounced during the days with a significant regional scale transport.

Temporal and Spatial Scales for Transport and Transformation Processes in the Eastern Mediterranean

In several studies during the past, the urban plumes have been extensively considered. In these studies, the spatial and temporal scales of episodic conditions have been described and emphasis was given to the formation and evolution of air pollution episodes within city limits (or in an area covering a few tens of kilometers around the city) and for a time period of one to two days. Moreover, the weather phenomena exhibiting strong diurnal variations (e. g. sea/land-breezes, upslope/downslope and drainage flows, orographic effects, heat islands etc.) were emphasized. The influence of the regional scale phenomena in such cases was not considered on a systematic manner. Actually, the role of phenomena with wavelengths larger than a few tens of kilometers was considered as not important for the formation of a specific air quality over the city of consideration. During the last few years, the influence of regional scale forcing on the formation of specific air quality conditions was found to be important. Kallos et al. (1993) reported that the regional scale phenomena should contribute significantly in the formation of specific air quality conditions in the Greater Athens Area (GAA). Luria et al. (1996) showed that significant degradation of the air quality in some areas should be attributed to regional scale transport phenomena. While the physicochemical properties of various urban plumes have been described at the urban scale with the aid of organized experimental campaigns and/or mesoscale and photochemical modeling (e. g. Ziomas, 1996), not enough attention was paid to the properties of the urban plume as it is passing to areas relatively far from its origin. Consequently, the urban plume impact on remote locations has not been extensively studied. Such phenomena should be considered as very important in some cases, especially in areas with specific characteristics like the Mediterranean Region.

Possible Mechanisms for Long Range Transport in the Eastern Mediterranean

The Mediterranean Sea is closed from all sides and has approximately an elliptical shape. Its major axis of about 3600 km has a W-E orientation, while the N-S width is variable from 200–800 km. It is surrounded by high peninsulas and important mountain barriers. The most important are the Alps and the Balcan Peninsula to the N, the Iberian Peninsula to the W, the Atlas Mountains to the SW, and the Asia Minor to the NE. The Asia Minor Plateau separates the Mediterranean from the Black Sea. The gaps between these major mountainous regions act as channels for the air mass transport from/to the Mediterranean. This kind of transport is considered as very important for the air quality in the Mediterranean Region. These topographic features along with the significant variation of the physiographic characteristics are partially responsible for the development of various-scale atmospheric circulations. These locally produced atmospheric circulations are quite strong, especially during the warm period of the year. The most significant from these regional to mesoscale circulations in the area are described in the publication of the UK. Meteorological Office “Weather in The Mediterranean”, (1962).

Modeling of Combined Aerosol and Photooxidant Processes in the Mediterranean Area

The combined UAM-AERO/RAMS modeling system has been applied to study the dynamics of photochemical gaseous species and particulate matter processes in the eastern Mediterranean area between the Greek mainland and the island of Crete. In particular, the modeling system is applied to simulate atmospheric conditions for two periods, i.e., 13-16 July 2000 and 26-30 July 2000. The spatial and temporal distributions of both gaseous and particulate matter pollutants have been extensively studied together with the identification of major emission sources in the area. New pre-processors were developed for the UAM-AERO model for evaluating detailed emission inventories for biogenic compounds, resuspended dust and sea salt. Comparison of the modeling results with measured data was performed and satisfactory agreement was found for a number of gaseous species. However, the model underestimates the PM10 measured concentrations during summer. This is mainly due to the considerable underestimation of particulate matter emissions and in particular dust resuspension, the effect of forest fire emissions and the contribution of Saharan dust episodes.

A Study of the Dispersion of Air Pollutants Released from Major Elevated Sources Located Near Athens, Greece

In the area around Athens is a number of elevated sources mainly power plants, refineries, cement plants etc. These industrial installations are using fuels of different types and characteristics. Almost all the examined installations are located near the coast and therefore the dispersion characteristics show significant spatial and temporal variations.

Photo-Oxidation Processes Over the Eastern Mediterranean Basin in Summer

In the present study, multi-scale analysis of the atmospheric circulation and photochemical processes was performed in order to investigate the behavior of photochemical plumes emitted from urban coastal areas. The simulations were combined with regional scale marine boundary layer airborne measurements of the atmospheric oxidants. The results showed a strong interaction between local and regional scale fluctuations. The previously identified main routes of transport were confirmed as routes of photochemical fluctuations. The key factor is the marine boundary layer. The plume maintains its characteristics inside this stable layer and the diurnal fluctuation of NOy in association with precursor VOCs define oxidant concentration at remote areas.