P. Katsafados

Long-Range Transport of Anthropogenically and Naturally Produced Particulate Matter in the Mediterranean and North Atlantic: Current State of Knowledge

Abstract During the past 20 years, organized experimental campaigns as well as continuous development and implementation of air-pollution modeling have led to significant gains in the understanding of the paths and scales of pollutant transport and transformation in the greater Mediterranean region (GMR). The work presented in this paper has two major objectives: 1) to summarize the existing knowledge on the transport paths of particulate matter (PM) in the GMR and 2) to illustrate some new findings related to the transport and transformation properties of PM in the GMR. Findings from previous studies indicate that anthropogenically produced air pollutants from European sources can be transported over long distances, reaching Africa, the Atlantic Ocean, and North America. The PM of natural origin, like Saharan dust, can be transported toward the Atlantic Ocean and North America mostly during the warm period of the year. Recent model simulations and studies in the area indicate that specific long-range tra...

Towards an Ocean Forecasting System for the Aegean Sea

A first approach towards an ocean forecasting system for the Aegean Sea is presented in this paper. The ocean forecasting component is part of the POSEIDON system which includes high resolution atmospheric and wave modeling of the Aegean Sea together with an extended network of observational buoys for the continuous monitoring of physical, biological and chemical parameters. The ocean forecast model system consists of a high-resolution (1/20° times; 1/20°) implementation of the Princeton Ocean Model (POM) forced by forecast surface fluxes of momentum, heat and freshwater provided by the regional ETA atmospheric model. The climatological runs of the model reproduce the basic features of the general circulation in the Aegean Sea. In the forecasting mode the model shows skill in forecasting the sea surface temperature (SST) phenomenology when compared with satellite-derived SST. Sensitivity tests (such as the inclusion of sea surface atmospheric pressure) have been performed in order to improve the models n...

Forecast errors in dust vertical distributions over Rome (Italy): Multiple particle size representation and cloud contributions

[1] In this study, forecast errors in dust vertical distributions were analyzed. This was carried out by using quantitative comparisons between dust vertical profiles retrieved from lidar measurements over Rome, Italy, performed from 2001 to 2003, and those predicted by models. Three models were used: the four-particle-size Dust Regional Atmospheric Model (DREAM), the older one-particle-size version of the SKIRON model from the University of Athens (UOA), and the pre-2006 one-particle-size Tel Aviv University (TAU) model. SKIRON and DREAM are initialized on a daily basis using the dust concentration from the previous forecast cycle, while the TAU model initialization is based on the Total Ozone Mapping Spectrometer aerosol index (TOMS AI). The quantitative comparison shows that (1) the use of four-particle-size bins in the dust modeling instead of only one-particle-size bins improves dust forecasts; (2) cloud presence could contribute to noticeable dust forecast errors in SKIRON and DREAM; and (3) as far as the TAU model is concerned, its forecast errors were mainly caused by technical problems with TOMS measurements from the Earth Probe satellite. As a result, dust forecast errors in the TAU model could be significant even under cloudless conditions. The DREAM versus lidar quantitative comparisons at different altitudes show that the model predictions are more accurate in the middle part of dust layers than in the top and bottom parts of dust layers.

Impact of coastal transportation emissions on inland air pollution over Israel: Utilizing numerical simulations, airborne measurements, and synoptic analyses

[1] The detection of high ozone levels over large inland areas in Israel during the early, mid and late summer triggered an analysis of air mass back-trajectories. This, in turn, pointed to the transportation system in the metropolitan coastal Tel Aviv region as the possible origin of the ozone’s precursors. To link the daily dynamics of rush hour transportation emissions to inland air pollution, in general, and airborne ozone measurements, in particular, an interdisciplinary modeling system was established. The simulations of transportation-to-inland air pollution integrated transportation, emission factor, atmospheric, transport/diffusion, and photochemical models. The modeling results elucidated a spatial and temporal overlap between the ozone precursors and ozone production. The model simulations indicated east to southeasterly dispersion of the pollution cloud. The results agreed well with both spatial and temporal ozone levels as recorded by aircraft over central Israel, as well as with ground-based monitoring station observations. The impact of the Tel Aviv metropolitan area as well as the Gaza Strip, as pivotal coastal transportation sources for inland air pollution in general and ozone formation in particular, is discussed. The synoptic analysis identified the conditions prevailing when elevated air pollution, and especially high ozone levels, exists over central Israel. The analysis showed that this season features a shallow mixed layer and weak zonal flow, which leads to poor ventilation rates and inhibit efficient dispersion of this secondary pollutant. These poor ventilation rates result in the slow transport of ozone precursors, enabling their photochemical transformation under intense solar radiation during their travel from the coast inland. Under these conditions, model results showed that traffic emissions during the morning rush hour from the Tel Aviv metropolitan area contribute about 60% to the observed ozone concentrations. INDEX TERMS: 0345 Atmospheric Composition and Structure: Pollution—urban and regional (0305); KEYWORDS: air pollution, numerical atmospheric modeling, transportation model, emission factors, photochemical model, ozone, photochemical aged air mass

Mapping long-term atmospheric variables over Greece

A gridded dataset representing near surface atmospheric fields has been developed to allow spatial analysis of long-term weather patterns over an area with significant climate spatiotemporal variability, Greece. The atmospheric elements considered are means of near surface temperature, means of relative humidity, as well as monthly and annual accumulated precipitation. The extracted patterns are based on the gridded European Centre for Medium-Range Weather Forecast (ECMWF) daily analyses interpolated on a regular 0.25° × 0.25° grid. Long-term means on annual and monthly bases for an 18-year reference period (1990–2007), are estimated for the continuous fields. Monthly and annual averages of accumulated precipitation for the period of 1980–2001 have also been created from near to analysis ECMWF forecasts and records gathered from surface meteorological stations. The extracted dataset has been accordingly formatted in order to allow visualization of the long-term atmospheric variables using a geographic information system.

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.

Contribution of Desert Dust Transport to Air Quality Degradation of Urban Environments Recent Model Developments

Mineral dust, produced by wind erosion over arid and semi-arid areas of North Africa, may transport away to the Middle East, Mediterranean, Europe, even into and across the Atlantic Ocean (Kallos et al., 2002). This material transported away from its origin is considered as an important climate and environment modifier. Dust particles by absorbing and backscattering both the incoming solar radiation and the infrared outgoing radiation modify the Earth’s radiation budget (Andreae, 1996). In addition, they alter the cloud microphysics processes acting as cloud condensation nuclei and having pH < 7.0 play a role in neutralization of the acid rains (Hedin and Likens, 1996). Also with the long-range dust transport, important nutrients are transported from their sources to other regions and may significantly modify the biogeochemistry of these marine and terrestrial ecosystems (Swap et al., 1996). For example, the deposition of the North African dust material on the Mediterranean Sea provides important nutrients, such as nitrogen species, phosphorus and iron, which may enhance the marine productivity. Some summer algal blooms in the Mediterranean Sea may be explained by such Saharan dust deposition (Dulac et al., 1996). Guerzoni et al. (1999) have estimated the amount of the atmospheric dust mass deposited on Mediterranean region to be ∼40×106 tons. Even though, they turned out to this magnitude by measured atmospheric mass flux at 9 coastal sites (which is considered as a small number of sites for such a work), this is considered as a valuable estimation since it is the only one found so far.

Model-derived seasonal amounts of dust deposited on Mediterranean Sea and Europe

Abstract The dust amounts deposited on the surface depends critically upon the seasonal varia- bility of the dust cycle in the atmosphere. Analyses of ground and satellite-based obser- vations can lead to useful results in relation to the seasonal variability of dust deposition. However, to gain a feeling of the magnitude and the geographical distribution of the dust deposition on ground surfaces and on coastal and open seas, the use of a credible numerical model is considered essential. In this study, using the SKIRON/Eta weather forecasting system, a database of seasonal amounts of dust deposited on Mediterranean Sea and Europe has been created.

Implementation of a Hybrid Surface Layer Parameterization Scheme for the Coupled Atmosphere-Ocean Wave System WEW

The two-way fully coupled atmosphere-ocean wave system WEW has been recently developed for studying the factors that contribute to the air-sea interaction processes and feedbacks. The new developed wind-wave parameterization scheme reduces both the near surface wind speed and the significant wave height as a response to the increased aerodynamic drag considered by the atmospheric model over rough sea surfaces. Such behavior is mainly attributed to the surface layer parameterization scheme of the atmospheric component which is based on the Mellor-Yamada-Janjic (MYJ) scheme. Therefore, we proceed to develop a new hybrid surface layer parameterization based on the MYJ and the Janssen schemes that operate in the atmospheric and ocean wave components of the WEW, respectively. In this case the roughness length depends on the wave age instead of the Charnock parameter following the formulation proposed by Drennan et al. (2003). The parameterization of the viscous sublayer and the universal functions for the estimation of the near surface wind speed have been accordingly revised. The new hybrid scheme has been statistically evaluated against buoys measurements and satellite retrievals across the Mediterranean Sea in a case study of high-impact weather and sea state event.