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AEGEAN_GAME2: AEGEAN Pollution: Gaseous and Aerosol airborne MEasurements

Start date: 29-08-2011 - End date: 08-09-2011

Status: Confirmed

Open to sharing: Yes

Confidential: No

Transnational Access: Yes

Open to training: Yes

Grounded / Maintenance: No


Aircraft name: BAe146 - FAAM

Airport: The flights will be performed over the Aegean Sea, Greece, between the northern part of Aegean Sea (island of Lesvos) and Crete. Aegean Sea offers a challenging domain to apply the atmospheric and chemistry transport models, as it is an area 1) with remarkably high levels of air pollution (from anthropogenic and natural sources that interact chemically) from the surface to the top of the troposphere and 2) where the Etesians winds, responsible for the pollution transport from distant sources, are more pronounced (Pinardi et al., 2005).

Project description

Project theme: Physical and chemical processes of polluted air masses over the Aegean Sea during summer period

Science context: Transport and transformation processes in the Eastern Mediterranean have been the topic of intensive studies that aim to evaluate their impact on regional air quality and visibility, climate and atmospheric composition change (e.g. Mihalopoulos, 2007; Hildebrandt et al., 2010; Pikridas et al., 2010). Though the proper incorporation of these processes in modelling systems is considered critical, it is not always so efficient (Tombrou et al., 2009). We propose to investigate the physical and chemical processing of polluted air transported over the Aegean troposphere during the Etesian winds, and to evaluate the representation of these processes in models of atmospheric composition and transport. The experiment will involve flights of long legs; near surface and close to PBL top, along the direction from Lesvos to Crete (figure) to sample the spatial structure of the atmospheric parameters and of the chemical concentrations. Deep profiles exceeding the PBL top and including 30 minute closed legs at two different levels will provide information regarding radiation balance and flow divergences and fluxes. The interpretation of the airborne measurements will be enriched by the analysis of in situ continuous air pollution and meteorological measurements on the islands of Lesvos and Crete. Furthermore, measurements using instruments onboard commercial vessels commuting across the Aegean Sea will be used. The measured physical parameters and chemical/aerosol concentrations will be compared with model predictions to assess their ability to capture various processes in the atmosphere over the Aegean Sea. This database will provide an excellent tool for further development of parameterization schemes.

Measurements to be made by aircraft: During the prevailing strong north-easterly winds (the so called ‘Etesians’, the most common synoptic situation that occurs over the Aegean Sea during summer), increased concentrations of gaseous pollutants and aerosol particles are observed, due to the simultaneous contribution of local and distant sources (Salisbury et al., 2003; Kalabokas et al., 2008). This complex mixture of fresh and aged pollution over the Aegean Sea, is mainly controlled by the wind field that is modified by the numerous islands of the Aegean Sea (channel and obstacle effects) and especially Crete (which is oriented perpendicular to the flow) during the Etesians (Kotroni et al., 2001). See also figure below. Previous experiments in the Aegean Sea, which also involve aircraft measurements, were in the framework of STAAARTE-MED and MINOS campaigns. The former covered a north-south path away from the Attica peninsula and easterly of Cyclades, without performing east-west transects (Formenti et al., 2002a; b). The measurement period took place over a decade ago (1998). Meteorological airborne data were not published, while the scientific concern for aerosol focuses on the relationship between SO2 and sulfates and on direct radiative forcing. Publications related to the MINOS campaign (MINOS special issue) show that flights provided in situ trace gas measurements, while aerosol is not involved in the research linked to this campaign (Ladstätter-Weißenmayer et al., 2003). Previous intensive studies focused mainly on the investigation of long range transport phenomena in the area (Formenti et al., 2002a; Lelieveld et al., 2002; Kocak et al., 2004; Kallos et al., 2007), whereas modelling experiments focusing on the linkage between concentration and atmospheric parameters have been performed mainly with global models (e.g. Roelofs et al., 2003; Lawrence et al., 2003; Scheeren et al., 2003). Recent results of coupling a regional to a global air pollution model have shown that the existing dynamic and chemical processes in modelling systems could not always efficiently represent the observed physical and chemical atmospheric conditions in this area (Tombrou et al., 2009). One of the main difficulties to diagnose the reasons for these discrepancies comes from the fact that only ground measurements are available, thereby limiting the mapping of the dynamic evolution of the PBL. These processes, therefore, warrant the availability of field measurements for the calibration of the models. Our objectives, which differentiate the proposed work from the aforementioned, are to: - Determine the meteorological atmospheric parameters including turbulence and consequently enhance the knowledge of the PBL evolution over the Aegean Sea, during an Etesian event. - Measure the current concentrations of gaseous pollutants as well as the physical and chemical properties of the suspended aerosol particles in the area. - Determine the photochemical oxidants and bulk aerosol entering the boundaries over the Aegean Sea, for regional modelling. - Determine ozone and SOA increases between the northern and the southern Aegean in order to investigate this ageing. - Evaluate the dynamic and chemical processes of atmospheric models towards efficient configuration of the physical and chemical profiles (and not just ground data) into the atmosphere of an area where local emissions, medium and long-range transport, as well as stratospheric intrusions shape the atmospheric regime. The currently proposed work aims at covering the greater Aegean area, through dedicated flights of the FAAM - BAe146 aircraft. Sea traffic emissions mainly around Cyclades and the Attica plume are critical to be involved in the study, as anthropogenic pollution mixes with sea-salt aerosol. The latter is already predicted to offer an important relationship between NO2 and nitrates, which is also into the research field of this study, unlike previous campaigns. The interpretation of the project results will be enriched by the analysis of ground measurements that will be conducted by the Water and Air Analysis Laboratory (Un. of the Aegean) on the island of Lesvos, sited at the northern Aegean, by the Environmental Chemical Processes Laboratory (Finokalia monitoring station, Un. of Crete) on the island of Crete at the southern Aegean, and onboard commercial vessels. The monitoring station on Lesvos will provide continuous measurements of gaseous species (i.e., concentrations of O3, NOx, and SO2), aerosol particle properties (i.e., size distributions, volatility, hygroscopicity, and optical properties) as well as meteorological parameters (temperature, relative humidity, wind speed and direction). The monitoring station at Crete will provide ground level measurements of gaseous pollutants (O3, NOx, and CO), various aerosol particle parameters (PM10 mass, mass and number size distributions, optical properties, chemical composition measurements), as well as meteorological parameters (temperature, relative humidity, wind speed and direction) . The AEGEAN_GAME data will add to the poor experimental data pool for the greater area of Greece. Furthermore, it will comprise a comprehensive description of the three-dimensional structure of both the PBL and pollutants concentrations over the Aegean Sea during Etesian synoptic conditions. Therefore, these data will be valuable to: - Improve knowledge on the current atmospheric composition and on chemical and dynamic processes occurring in the PBL over the Aegean, during the Etesian regime. - Validate the atmospheric (WRF) and chemistry transport models (CAMx or WRF-CHEM) under the Etesian synoptic conditions. - Identify areas of parameterization, which are poorly treated in relation to requirements for air pollution and dispersion applications. - Improve and validate several parameterization schemes of physical and chemical processes in models (e.g. the radiative transfer code, mixing processes, photolysis rates). In particular, data will be used to explain how efficient do the entrainment mechanism bring air from the dry quasi laminar free atmosphere, into the moist turbulent boundary layer and the role of the existing barriers (islands) to the flow. - Identify the main requirements for the initial and boundary conditions. The testing of the models dynamics description will be further supported by diagnostic evaluation (Russell and Dennis, 2000). Specifically, regarding gas-phase chemistry, in situ measurements of indicator species will be used either directly to infer aspects of processes in the atmosphere, or to compare against model-predicted values. For aerosols, the proposed instruments will provide information on their chemical composition as well as the interaction between natural (e.g. sea salt) and anthropogenic (e.g. ship emissions) sources. The information will be used to compare with predicted size-resolved aerosol chemical concentrations (e.g. sulfate, nitrate, ammonium, POA, PEC, SOA, sodium, chloride, crustal; ISORROPIA II and SOAP schemes are used for the partitioning of inorganic and secondary organic aerosols, respectively). The model results will be further elucidated by using Ozone Source Apportionment Technology module to identify the origin of pollution. The vertical profiles of the aerosol, total particle number and size distribution, in combination with the radiation measurements will be used to validate several radiative transfer codes, already included in the meteorological and chemical models, particularly the diffuse radiation, which is generally overestimated by models (Noorian et al., 2008). Refereed publications in pre-reviewed journal and conference presentations are planned for the dissemination of the scientific results. Several researchers could also use the database in the future.

Season: 15/07/2011- 20/08/2011. We are flexible on dates

Weather constraints: Etesians is the most common synoptic condition that occurs over the Aegean Sea, during summer (especially in July and August), with prevailing winds from the north-eastern direction and clear skies.

Time constraints: Periods during summer, morning and afternoon hours to study the evolution of the PBL structure and the chemical processes

Flights (number and patterns): The target area of the aircraft measurements will cover the Aegean area (TR corner: 39°04’40”, 26°35’27”, (Mytilene airport); BL corner: 35°20’11”, 25°08’26”, (Heraklion airport, Crete). In total, a minimum of 15 flight hours are requested that correspond to three aircraft missions (~5hrs per mission). The aircraft is proposed to take off from the island of Crete and perform the two flights, measuring at two predefined levels along the main wind direction a) a straight leg near the surface towards the island of Mytilene and b) an intermittent leg close to PBL top with successive paths directly above and below the PBL top (every 50 km) back to Crete. Flights will also involve deep profiles exceeding the PBL top, incorporating 30 minute closed legs (about 50 km diameter) at two different levels (below and above PBL top); a) in the north of Crete and b) approximately halfway between Lesvos and Crete. One flight is proposed during the morning hours (~ 0500–1100LT) and the second one during the afternoon hours (~ 1300-1800LT). A supplementary third flight is proposed to cover east-west transects above the greater Cycladic area during daylight (~1100-1600LT).

Instruments: Information is included in the attached file FAAM-Instruments An Aerodyne Compact Time of Flight Aerosol Mass Spectrometer (C-AMS) is already part of the FAAM BAE-146 fit and has successfully flown in a number of studies since 2004 (Crosier et al 2007; Capes et al., 2008; Morgan et al., 2010a and Morgan et al., 2010b). The instrument has already been approved on the aircraft and has a standalone data system. The University of Manchester also maintain and operate a Scanning Mobility Particle Sizer (SMPS) on the same rack as the C-AMS. UOM will also operate this instrument for AEGEAN-GAME. A DMT Single particle soot photometer uses an intra cavity laser to heat and subsequently incandesce absorbing particles. The light from the incandescence is proportional to the mass of BC in a single particle. Information on the mixing state of black carbon can also be obtained. This instrument has been successfully operated on the BAE-146 aircraft for the last 3 years (McMeeking et al., 2010). The University of Manchester has agreed to provide an operator for these instruments.

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