An Operational System For Monitoring Oil Spills In The Mediterranean Sea: The PROMED System

The primary objective of this work was the development of an operational system for early detection of oil-spills, monitoring of their evolution, and provision of support to responsible Public Authorities during cleanup operations, based on Remote Sensing and GIS technologies. In case of emergency, the principal characteristics of the oil spill are defined with the aid of a space-borne synthetic aperture radar (SAR). The transport, spreading and dispersion of the oil spill is subsequently simulated on the basis of wind forecasts of the area. The use of thematic maps of protected, fishing and urban areas, and regions of high tourism allows the better assessment of the impact of an oil spill on the areas to be affected in terms of environmental sensitivity. Finally, reports are generated notifying port authorities, the media, and local organizations to be potentially affected by the presence of the oil spill. The pilot site for testing the PROMED System in Greece is the island of Crete

Mini-acoustic sounding - A powerful tool for ABL applications: Recent advances and applications of acoustic mini-sodars

Atmospheric acoustic mini-sodar design characteristics, operating conditions and applications are described. Emphasis is given to the recent high space and time resolution applications in the field of the atmospheric boundary layer (ABL), such as wind energy, internal boundary layer, microclimate studies, etc. Special mention is made on modern data processing and layer classification techniques, which in association with the high space resolution characteristics of the instrument make a powerful tool for detailed ABL research. © 1996 Kluwer Academic Publishers

Some observations on the destruction of the morning temperature inversions in a large and broad mountain valley

Observations of the vertical thermal and wind structure made in a large and broad valley are reported here. The growth of the convective boundary layer is found to be responsible for the destruction of the nocturnal temperature inversion. No sinking of the inversion layer was observed in response to the morning upslope flow following the profiles of both potential temperature and wind data. These observations alongside previous published work do not permit a generalization of the behaviour of the flow and thermal structure for all valleys. Characteristics like the length, the depth and the ridgetop width of the valley play an important role to the mechanism of the destruction of the temperature inversion. -Author

Some observations on the destruction of the morning temperature inversions in a large and broad mountain valley

Observations of the vertical thermal and wind structure made in a large and broad valley are reported here. The growth of the convective boundary layer is found to be responsible for the destruction of the nocturnal temperature inversion. No sinking of the inversion layer was observed in response to the morning upslope flow following the profiles of both potential temperature and wind data. These observations alongside previous published work do not permit a generalization of the behaviour of the flow and thermal structure for all valleys. Characteristics like the length, the depth and the ridgetop width of the valley play an important role to the mechanism of the destruction of the temperature inversion. -Author

Estimation of the linke and Unsworth-Monteith turbidity factors in the visible spectrum: Application for Athens, Greece

Expressions for the Linke, T(Lvis), and Unsworth-Monteith, T(Uvis), turbidity parameters in the visible region of the solar spectrum are derived. They are based on new determinations of the visible transmittances for the various atmospheric constituents obtained by spectrally integrating the wavelength-dependent atmospheric transmittances. Application of the T(Lvis) and T(Uvis) expressions for Athens is made for the first time; this is done from measurements of direct solar irradiance in the period 1992-1995. A linear interdependence between T(Lvis) and T(Uvis) is derived, as in the case of their broadband counterparts. The seasonal, monthly and daily variations of these turbidity parameters are also investigated. Expressions for the Linke, TLvis, and Unsworth-Monteith, TUvis, turbidity parameters in the visible region of the solar spectrum are derived. They are based on new determinations of the visible transmittances for the various atmospheric constituents obtained by spectrally integrating the wavelength-dependent atmospheric transmittances. Application of the TLvis and TUvis expressions for Athens is made for the first time; this is done from measurements of direct solar irradiance in the period 1992-1995. A linear interdependence between TLvis and TUvis is derived, as in the case of their broadband counterparts. The seasonal, monthly and daily variations of these turbidity parameters are also investigated

Evaluation of minisodar performance operating in high wind conditions

The performance of a high resolution tristatic minisodar is evaluated over an area of complex topography using a 30m high meteorological mast equipped with cup anemometers and bivanes. The instrumentation was in operation at the Moni Toplou Wind Park (Island of Crete, Greece) and the comparison covered a range of high wind speed and different meteorological conditions during day and night-time periods. The Sodar measurements of mean wind speed and direction for 15 min time segments agreed with the in situ measurements although an underestimation of the wind speed is evident. On the other hand the standard deviations of the wind speed and direction as estimated by Sodar gave poor agreement with the in situ instrumentation. © 1997 Taylor & Francis Group, LLC

Inland propagation of sea breeze under opposing offshore wind

According to past experience, the nearly stagnant conditions by the presumed equilibrium between the Saronikos Gulf sea breeze and an opposing synoptic flow is identified as the principal mechanism leading to high pollution episodes in Athens during the summer. However, previous experimental work has not examined in detail the interaction of the sea breeze flow with the opposing background flow. In this context, recent experimental work covering the basic key-locations of the Athens Basin focused on the inland propagation of the southerly sea breeze from the coast to the northern part of the basin mainly under moderate northerly background wind. During this campaign, a network of four meteorological stations established along the Athens Basin and a high range acoustic sounder at the centre of Athens operated over a two months time period in the summer of 1993. In addition, tethered balloon flights in the centre of Athens and on a sea vessel about 15km offshore were employed during an experimental day with moderate opposing background wind. The results from this experimental campaign include the documentation of the sea breeze delay and its intensity as a function of a breeze index and features of the vertical structure of the sea breeze over land as well as over sea

MICROSTRUCTURE AND PROPERTIES OF Al-Li-Cu-Mg-Zr (8090) HEAVY SECTION FORGINGS

The microstructure and properties of heavy section forgings of the 8090 Al-Li alloy were investigated including the as-cast, homogenized, forged, and heat-treated conditions. The ingots, 305x965x2000-3600 mm in size, were cast by Alcan. Homogenization involved 24 to 48 h soaks at 545°C. Ingots were hand-forged by HDAF Ltd. to sizes up to 356x356x1524 mm, then solution-treated at 530°C for 6 h and water quenched. The material was aged at various times at temperatures of 150, 170, and 190°C. Microstructures were examined by TEM, CBED, SEM, AES, and optical microscopy. Mechanical properties were characterized by tensile, fracture toughness, and stress corrosion tests. A strong correlation was observed between grain boundary precipitation of a icosohedral (I) phase and certain mechanical properties. The I-phase has been tentatively identified as Al6CuLi3, historically called "T2". When the I-phase was predominant, the fracture toughness, SCC, and tensile ductility were invariably low. Factors identified as promoting the formation of I-phase were cooling rates from the solution treatment temperature slower than -10°C s-1, increased aging time, and increased aging temperatures in the range 150 to 190°C. Aging conditions which minimized the formation of the grain boundary I-phase and, consequently, improved the mechanical properties were determined. Three distinct constituent phases were found in cast ingots having only slightly different chemistries. Remnants of these constituent phases were present in every subsequent stage of thermal processing. One, AlLiSi, was discovered to promote surface pitting and to substantially lower the stress corrosion cracking resistance. This phase's reactivity with seawater appears to promote dissolution of the adjacent matrix. Material heat-treated to suppress the formation of the I-phase, but high in silicon, revealed low SCC resistance. In summary, many factors including composition, casting practice, metal-working, and heat-treatment, determine the mechanical properties of 8090 Al-Li in heavy section forgings, and which range from unacceptable to acceptable for high performance aerospace structures

An operational system for monitoring oil spills in the mediterranean Sea: The PROMED system

The primary objective of this work was the development of an operational system for early detection of oil-spills, monitoring of their evolution, and provision of support to responsible Public Authorities during cleanup operations, based on Remote Sensing and GIS technologies. In case of emergency, the principal characteristics of the oil spill are defined with the aid of a space-borne synthetic aperture radar (SAR). The transport, spreading and dispersion of the oil spill is subsequently simulated on the basis of wind forecasts of the area. The use of thematic maps of protected, fishing and urban areas, and regions of high tourism allows the better assessment of the impact of an oil spill on the areas to be affected in terms of environmental sensitivity. Finally, reports are generated notifying port authorities, the media, and local organizations to be potentially affected by the presence of the oil spill. The pilot site for testing the PROMED System in Greece is the island of Crete