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Temporal and Spatial Scales for Transport and Transformation Processes in the Eastern Mediterranean
Abstract
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.
... 176 P. Kalkavouras et al.: New Particle Formation in the southern Aegean Sea Sea (AS), which is part of the EM, has led to a number of experimental campaigns during the warm period (Mihalopoulos et al., 1997;Paronis et al., 1998;Formenti et al., 2002a, b;Kouvarakis et al., 2002;Lelieveld et al., 2002;Zerefos et al., 2002), focusing initially on the interpretation of ozone (O 3 ) enhancement under the Etesian regime. Apart from the simultaneous contribution of local and distant sources in the area, in the presence of enhanced photochemistry, strong subsidence was also identified in most of these events (Kallos et al., 1998(Kallos et al., , 2007Lelieveld et al., 2002;Salisbury et al., 2003;Kalabokas et al., 2007Kalabokas et al., , 2008Kalabokas et al., , 2013Kanakidou et al., 2011;Bossioli et al., 2016). Airborne measurements performed during an Etesian outbreak (Aegean-GAME campaign; Tombrou et al., 2015) clearly showed that neutral to stable atmospheric conditions prevailed over the northern and central AS, with reduced friction velocities and absolute turbulent fluxes (momentum or heat) cumulating the concentrations below the planetary boundary layer (PBL) and mainly inside the shallow marine atmospheric boundary layer (MABL). ...
This study examines how new particle formation (NPF) in the eastern Mediterranean in summer affects CCN (cloud condensation nuclei) concentrations and cloud droplet formation. For this, the concentration and size distribution of submicron aerosol particles, along with the concentration of trace gases and meteorological variables, were studied over the central (Santorini) and southern Aegean Sea (Finokalia, Crete) from 15 to 28 July 2013, a period that includes Etesian events and moderate northern surface winds. Particle nucleation bursts were recorded during the Etesian flow at both stations, with those observed at Santorini reaching up to 1.5 × 104 particles cm−3; the fraction of nucleation-mode particles over Crete was relatively diminished, but a higher number of Aitken-mode particles were observed as a result of aging. Aerosol and photochemical pollutants covaried throughout the measurement period; lower concentrations were observed during the period of Etesian flow (e.g., 43–70 ppbv for ozone and 1.5–5.7 µg m−3 for sulfate) but were substantially enhanced during the period of moderate surface winds (i.e., increase of up to 32 for ozone and 140 % for sulfate). We find that NPF can double CCN number (at 0.1 % supersaturation), but the resulting strong competition for water vapor in cloudy updrafts decreases maximum supersaturation by 14 % and augments the potential droplet number only by 12 %. Therefore, although NPF events may strongly elevate CCN numbers, the relative impacts on cloud droplet number (compared to pre-event levels) is eventually limited by water vapor availability and depends on the prevailing cloud formation dynamics and the aerosol levels associated with the background of the region.
We examine the concentration levels and size distribution of submicron aerosol particles along with the concentration of trace gases and meteorological variables over the central (Santorini) and south Aegean Sea (Crete) from 15 to 28 July 2013, a period that includes Etesian events and moderate northern winds. Particle nucleation bursts were recorded during the Etesian flow at both stations, with those observed at Santorini reaching up to 1.5 × 104 particles cm−3. On Crete (at Finokalia station), the fraction of nucleation-mode particles was diminished, but a higher number of Aitken-mode was observed as a result of the downward mixing and photochemistry. Aerosol and photochemical pollutants covaried throughout the measurement period: lower concentrations were observed during the period of strong Etesian flow (e.g. 43–70 ppbv for ozone, 1.5–5.7 μg m−3 for sulfate), but were substantially enhanced during the period of moderate winds (i.e., increase of up to 32 % for ozone, and 140 % for sulfate). To understand how new particle formation (NPF) affects cloud formation, we quantify its impact on the CCN levels and cloud droplet number concentration. We find that NPF can double CCN number (at 0.1 % supersaturation) but the resulting strong competition for water vapor in cloudy updrafts decreases maximum supersaturation by 14 % and augments the potential droplet number only by 12 %. Therefore, although NPF events may strongly elevate CCN numbers, the relative impacts on cloud droplet number (compared to pre-event levels) is eventually limited by water vapor availability and depends on the prevailing cloud formation dynamics and the aerosol levels associated with the background in the region.
The Black Sea is closed from all sides by land and communicates with the Aegean Sea and Mediterranean through the Vosporous strait (Fig. 1). It is surrounded by land with elevation varying from a few meters to a few kilometers. The most important orographic features are located at the eastern and south-eastern sides. More specifically, there is the Caucasus Peninsula in the East and the Pontine Mountains across the northern Turkish coast. Towards west, there is the opening of the Danube Valley with the Carpathian mountains to the North of it and the Balkan Peninsula to the South in a considerable distance from the coast. The northern part is adjacent to almost flat land with relatively complicated coastline. At a larger distance, the Balkan and Asia Minor Peninsulas together with the Aegean Sea between them and the Mediterranean Region in general are forming a unique pattern for the development of atmospheric circulations of a wide spectrum ranging from the synoptic to meso-gamma scale with significant implications to the air quality of the region.
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.
The physical and chemical processes involved in the mercury cycle in the atmosphere are very complicated and need special treatment. At the framework of the EU/DG-XII project MAMCS a significant effort has been devoted for the development of appropriate models for studying the mercury cycle in the atmosphere. In addition, an improved emission inventory is created while monitoring data in various locations in Europe are selected and used for model calibration and inter-comparison. Our model development includes the incorporation of almost any type of source (point or area), gas and aqueous phase chemistry, gas-to-particle conversion, wet and dry deposition, air-water exchange processes etc. The development was performed within two well-known atmospheric modeling systems: the Regional Atmospheric Modeling System (RAMS) and the SKIRON/Eta. There are several reasons for performing the development of the mercury cycle modeling within these two models: The main reason for using RAMS is its unique capability of two-way interactive nesting of any number of grids which is considered as absolutely necessary for studying near-source dispersion of mercury species. Additional capabilities are the full microphysical parameterization for wet processes, the detailed parameterization of surface processes and the non-hydrostatic formulation. The main reason for using the SKIRON/Eta model for development is its unique capability of describing the dust cycle (uptake, transport, deposition) and the existence of a viscous sub-layer formulation which is necessary for description of mercury fluxes from the sea surface. In both models the mercury cycle formulation is called simultaneously at each time-step in order
The Mediterranean Atmospheric Mercury Cycle System (MAMCS) project was performed between 1998 and 2000 and involved the collaboration of universities and research institutes from Europe, Israel and Turkey. The main goal of MAMCS was to investigate dynamic processes affecting the cycle of mercury in the Mediterranean atmosphere by combining ad hoc field measurements and modelling tasks. To study the fate of Hg in the Mediterranean Basin an updated emission inventory was compiled for Europe and the countries bordering the Mediterranean Sea. Models were developed to describe the individual atmospheric processes which influence the chemical and physical characteristics of atmospheric Hg, and these were coupled to meteorological models to examine the dispersion and deposition of Hg species in the Mediterranean Basin. One intercomparison and four two-week measurement campaigns were carried out over a three-year period. The work presented here describes the results in general terms but focuses on the areas where definite conclusions were unforthcoming and thus highlights those aspects where, in spite of advances made in the understanding of Hg cycling, further work is necessary in order to be able to predict confidently Hg and Hg compound concentration fields and deposition patterns.
The atmospheric part of the mercury cycle is considered as very complicated because of the various physicochemical processes involved. The temporal and spatial scales of various processes are varying according to mercury species. While Hg
0 is considered as long-range transport pollutant, Hg
II is fast reacting and deposits quickly (wet and dry). Hg
P
has behaviour similar to the other particulate in the atmosphere. There is enough evidence now about the various disturbances in what are considered as background quantities. The most important reasons are (i) the increase of emissions from sources like coal burning, waste incinerators, cement production, mining etc, (ii) the lack of understanding of important physicochemical processes like fluxes, transport, transformation and deposition. Because of these verified disturbances, during the last years, a considerable effort has been devoted to reduce the mercury emissions. At the framework of the EU/DG-XII project MAMCS a significant effort has been devoted at the development of appropriate models for studying the mercury cycle in the atmosphere. The model development is performed within the atmospheric models RAMS and SKIRON/Eta. In this development we tried to transfer and utilize the modeling techniques applied in conventional air pollution modelling studies. In addition, we had to develop new methodologies for processes like re-emissions from soil and water bodies and gas to particle formation. The developed modeling systems have been applied in the Mediterranean Region where the multi-scale atmospheric processes (thermal and mechanical circulations at regional and mesoscale) are considered as important, according to a number of past air pollution studies. Seasonal-type of simulation has been performed and annual deposition patterns have been estimated. As it was found, the regional-scale pattern and the trade wind systems (from North to South) and the photochemistry are the key factors for controlling the mercury deposition, especially the Hg
P
.
Based on regular climatological and air quality data from the Greater Athens Area (GAA), the air pollution episodes observed
in Athens during the period 1983–1990 were analysed and classified. The main characteristics of atmospheric conditions during
days with high air pollution concentrations are summarized too. Model simulations show that the worst air pollution episodes
in Athens occur during days with a critical balance between synoptic and mesoscale circulations and/or during days with warm
advection in the lower troposphere.
This paper presents a range of applications of the Regional Atmospheric Modeling System (RAMS), a comprehensive mesoscale meterological modeling system. Applications discussed in this paper include large eddy simulations (LES) and simulations of thunderstorms, cumulus fields, mesoscale convective systems, mid-latitude cirrus clouds, winter storms, mechanically- and thermally-forced mesoscale systems, and mesoscale atmospheric disperision. A summary of current RAMS options is also presented. Improvements to RAMS currently underway include refinements to the cloud radiation, cloud microphysics, cumulus, and surface soil/vegetative parameterization schemes, the parallelization of the code, development of a more versatile visualization capability, and research into meso--scale cumulus parameterization.
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).
Recent advances in computer technology have now placed supercomputer power on the desktop for a small fraction of the price. Many traditional supercomputer applications have benefited greatly in the move from the realm of the supercomputer center to more direct local control of the end user. Two of the atmospheric applications that have and will continue to benefit greatly from these advances in computer technology is in the arenas of local weather forecasting and emergency response systems.
Particulate sulfate has been measured intermittently at various ground sites in Israel and from an instrumented aircraft for a 10-year period between 1984 and 1993. The measurements were accompanied by concurrent monitoring of primary and secondary air pollutants and meteorological parameters. In three studies, Etzion 1984-1986, Jerusalem 1987-1988, and Jerusalem 1990-1991, measurements were taken for at least a year. The other studies were performed during summer months when higher levels of secondary pollutants, including particulate sulfate, were observed. In most of the studies samples were taken for four sequential 6-hour time segments. In one study, at Caesarea 1993, sulfate samples were taken only when wind flows were perpendicular to the coastline. The airborne measurements were performed along three north-south paths inside the planetary boundary layer, over the Mediterranean coast, over the Judea-Samaria mountains and over the Jordan Valley. Each flight path consisted of 30 to 45 minutes of continuous sampling of SO2 and one integrated sample of particulate sulfate. In all of our studies the concentration of particulate sulfate observed was relatively high compared with other world locations. The highest values, occasionally exceeding 500 nmolem-3, were found during the summer. Wintertime levels were in the range of 50-100 nmolem-3. The annual average, calculated for the three long studies, is 100+/-15 nmolem-3, which is twice as high as predicted for the region by a global model and as high as reported for some of the more polluted regions in the US. Several indicators suggested that the origin of the sulfate in the region is not from local sources but the result of long range transport. The indicators include the lack of correlation between particulate sulfate and primary pollutants, the high sulfate to total sulfur values, the origin of the airmass back trajectories and the fact that similar levels were observed during concurrent periods at different sites. Throughout the study, higher concentration of particulate sulfate was found during the afternoon hours, especially during the summer and at the inland locations. The contribution to the afternoon elevated values could not be associated with long range transport and results probably from major sulfur emission sources located along the Israeli Mediterranean coast.
The MEDCAPHOT-TRACE experiment took place in the Greater Athens Area (GAA) during the summer of 1994 (20 August–20 September) with the participation of 16 European scientific groups. The purpose of MEDCAPHOT-TRACE was to study the chemical and meteorological evolution of ozone and related trace gases (over land and sea), modulated by the various synoptic and local meteorological conditions (sea/land breeze circulation, local winds, inversion layers, etc.) in one of the largest urban agglomerations in the Mediterranean region. In addition to the operating stations of the existing air pollution monitoring network, 18 new stations operated in the vicinity of the GAA. The scientific instrumentation used in the experiment consisted of ground-based air pollution measuring systems (gas analysers and gas chromatographs), integrated-path air pollution measuring systems (DOAS systems), ground-based laser remote sensing systems (LIDAR technique), meteorological instrumentation (slow- and fast-response) and aircraft measurements (air pollution and meteorological). Although the monitoring programme was intensified during the 10 d period of aircraft measurements, the larger proportion of measurements was carried out on a regular day-and-night basis throughout the 30 d period of the campaign. The data collected cover a variety of meteorological situations and will be made available for general use in the near future. An introduction to some of the results are given in the following.
South European Cycles of Air Pollution(SECAP). Final Report prepared for the DGXII
- G Kallos
- V Kotroni
- K Lagouvardos
- M Varinou
- A Papadopoulos
An emergency response and local weather forecasting software system. Preproceedings of the 20th ITM on Air Pollution and its Application
- C J Tremback
- W A Lyons
- W P Thorson
- R L Walko
Mesometeorological Cycles of Air Pollution in the Iberian Peninsula. Final Report for the DGXII of EU
- M Millan
- B Artinano
- L Alonso
- M Castro
- R Fernandez-Patier
- J Goberna