Validation of OMI erythemal doses with multi-sensor ground-based measurements in Thessaloniki, Greece

The aim of this study is to validate the Ozone Monitoring Instrument (OMI) erythemal dose rates using ground-based measurements in Thessaloniki, Greece. In the Laboratory of Atmospheric Physics of the Aristotle University of Thessaloniki, a Yankee Environmental System UVB-1 radiometer measures the erythemal dose rates every minute, and a Norsk Institutt for Luftforskning (NILU) multi-filter radiometer provides multi-filter based irradiances that were used to derive erythemal dose rates for the period 2005–2014. Both these datasets were independently validated against collocated UV irradiance spectra from a Brewer MkIII spectrophotometer. Cloud detection was performed based on measurements of the global horizontal radiation from a Kipp & Zonen pyranometer and from NILU measurements in the visible range. The satellite versus ground observation validation was performed taking into account the effect of temporal averaging, limitations related to OMI quality control criteria, cloud conditions, the solar zenith angle and atmospheric aerosol loading. Aerosol optical depth was also retrieved using a collocated CIMEL sunphotometer in order to assess its impact on the comparisons. The effect of total ozone columns satellite versus ground-based differences on the erythemal dose comparisons was also investigated. Since most of the public awareness alerts are based on UV Index (UVI) classifications, an analysis and assessment of OMI capability for retrieving UVIs was also performed. An overestimation of the OMI erythemal product by 3–6% and 4–8% with respect to ground measurements is observed when examining overpass and noontime estimates respectively. The comparisons revealed a relatively small solar zenith angle dependence, with the OMI data showing a slight dependence on aerosol load, especially at high aerosol optical depth values. A mean underestimation of 2% in OMI total ozone columns under cloud-free conditions was found to lead to an overestimation in OMI erythemal doses of 1–5%.While OMI overestimated the erythemal dose rates over the range of cloudiness conditions examined, its UVIs were found to be reliable for the purpose of characterising the ambient UV radiation impact

Study of the pollution exchange between Bulgaria and northern Greece

The present work aims at a detailed study and explanation of the pollution transport in the air basin over south-western Bulgaria and northern Greece and assessment of the air pollution exchange between Bulgaria and Greece. Some well-known specific climatic air pollution effects were studied and explained. Calculations were made of the SO2 pollution of the Balkan Peninsula from both Greek and Bulgarian sources for 1995, and the country-to-country pollution budget diagrams were built. Days with extreme mean concentration for Bulgaria and northern Greece were picked out, and some further specification of the contribution of the different sources in both the countries to these cases of extreme pollution was made. Some preliminary studies of possible mesoscale effects on the pollution exchange between Bulgaria and northern Greece were carried out. A three-layer pollution transport model with a more complex chemistry block was introduced, and some preliminary simulations of the transport of sulfur and nitrogen compounds were performed

Study of the pollution exchange between Bulgaria and northern Greece

The present work aims at a detailed study and explanation of the pollution transport in the air basin over south-western Bulgaria and northern Greece and assessment of the air pollution exchange between Bulgaria and Greece. Some well-known specific climatic air pollution effects were studied and explained. Calculations were made of the SO2 pollution of the Balkan Peninsula from both Greek and Bulgarian sources for 1995, and the country-to-country pollution budget diagrams were built. Days with extreme mean concentration for Bulgaria and northern Greece were picked out, and some further specification of the contribution of the different sources in both the countries to these cases of extreme pollution was made. Some preliminary studies of possible mesoscale effects on the pollution exchange between Bulgaria and northern Greece were carried out. A three-layer pollution transport model with a more complex chemistry block was introduced, and some preliminary simulations of the transport of sulfur and nitrogen compounds were performed

STAAARTE-MED 1998 summer airborne measurements over the Aegean Sea: 2. Aerosol scattering and absorption, and radiative calculations

[1] Chemical, physical, and optical measurements of aerosol particle properties within an aged biomass-burning plume were performed on board a research aircraft during a profile descent over a ground-based site in northeastern Greece (40degrees24'N, 23degrees57'E; 170 m asl) where continuous measurements of the spectral downwelling solar irradiance (global, direct, and diffuse) are being made. The aerosol optical depth measured at the ground during the time of overflight was significantly enhanced (0.39 at a wavelength of 500 nm) due to a haze layer between 1 and 3.5 km altitude. The dry particle scattering coefficient within the layer was around 80 Mm(-1), and the particle absorption coefficient was around 15 Mm(-1), giving a single scattering albedo of 0.89 at 500 nm (dry state). The black carbon fraction is estimated to account for 6-9% of the total accumulation mode particle mass (<1 μm diameter). The increase of the particle scattering coefficient with increasing relative humidity at 500 nm is of the order of 40% for a change in relative humidity from 30 to 80%. The dry, altitude- dependent, particle number size distribution is used as input parameter for radiative transfer calculations of the spectral short-wave, downwelling irradiance at the surface. The agreement between the calculated irradiances and the experimental results from the ground-based radiometer is within 10%, both for the direct and the diffuse components (at 415, 501, and 615 nm). Calculations of the net radiative forcing at the surface and at the top of the atmosphere (TOA) show that due to particle absorption the effect of aerosols is much stronger at the surface than at the TOA. Over sea the net short-wave radiative forcing (daytime average) between 280 nm and 4 μm is up to -64 W m(-2) at the surface and up to -22 W m(-2) at the TOA

Signification pronostique de l'envahissement occulte du ganglion sentinelle dans le mélanome cutané

ST ETIENNE-BU Médecine (422182102) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF