The Experts below are selected from a list of 1962 Experts worldwide ranked by ideXlab platform
G De Sadelaer - One of the best experts on this subject based on the ideXlab platform.
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photochemical ozone production in the convective mixed layer studied with a tethered Balloon Sounding system
Journal of Geophysical Research, 1997Co-Authors: Dirk De Muer, René Heylen, M Van Loey, G De SadelaerAbstract:In 1987, 1988, and 1990, four measuring campaigns with a tethered Balloon Sounding system were performed in a semirural area in Belgium to study the ozone distribution in the boundary layer in relation to meteorological parameters, during episodes of photochemical ozone production in the convective mixed layer. The detailed profiles of the ozone concentration between sunrise and sunset were used for a calculation of the change rate of the ozone column density in the boundary layer. These values allowed us to determine for the first time the integrated ozone production rates in the convective mixed layer, making use of a simplified form of the continuity equation of ozone mass. From all the measuring campaigns a range of integrated ozone production rates from 0 to 9 μg m−2 s−1 was found. Peak values of the ozone production rate were observed when the direct solar radiation intensity rises for the first time in the course of a day to about 400 W m−2 before noon. The upper envelope of a scatterplot of all ozone production rates as a function of the direct solar radiation shows a linear course up to about 650 W m−2. Beyond this value the intensity of direct solar radiation is no longer a rate-limiting factor in the photochemical ozone production process in the boundary layer; under these conditions the ozone production is limited by the supply rate of hydrocarbons. In general, the measured ozone production rates also show an increase with increasing ambient temperatures. At temperatures larger than 24°C the integrated net ozone production rate during the campaigns was always at least 3 μg m−2 s−1 when the direct solar radiation values were larger than 350 W m−2 . The surface ozone deposition velocity at the site of the campaigns was determined from the ozone data through an indirect method that does not require any parameterization of the vertical ozone flux; at daylight conditions an upper limit of 1.4 cm s−1 was found.
Zouhair Benkhaldoun - One of the best experts on this subject based on the ideXlab platform.
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meteorological profiles and optical turbulence in the free atmosphere with ncep ncar data at oukaimeden i meteorological parameters analysis and tropospheric wind regimes
Monthly Notices of the Royal Astronomical Society, 2012Co-Authors: Y. Hach, M. Sabil, A. Jabiri, A. Abahamid, Aziza Bounhir, A Ziad, Zouhair BenkhaldounAbstract:In this paper, we have used the National Centers for Environmental Prediction (NCEP)/National Centers for Atmospheric Research (NCAR) Reanalysis data base to study, first, a comparison between Balloon Sounding made at different stations with coinciding model-based meteorological analysis. The comparison allows the assessment of reliability of the analysis in the studied period and to highlight NCEP/NCAR Reanalysis as an interesting data base for site characterization. Using the same system of Reanalysis, we present, secondly, the first complete characterization of main meteorological parameters at Oukaimeden Observatory: wind speed, its direction, temperature and pressure. The statistical treatment of data will cover the years between 1990 and 2009. Monthly, seasonal and annual results are analysed. The comprehensive and reliable statistics of tropospheric wind speeds at Oukaimeden are presented. We found a clear annual periodicity of 200 mbar wind speed. This periodicity could be related to the seasonal dependence of seeing that is affected by the existence of cloud sea during the period around autumn–winter and by high wind speed regimes during spring. The connection of high- to low-altitude tropospheric winds has been explored. We found a high correlation comparable to the ones found at La Silla and La Palma sites. The local parameters in particular topography and stratocumulus formations might affect 700 mbar wind roses. Richardson numbers calculated for each month at Oukaimeden and La Palma are presented. By analysing the values, we found out that the periods and the regions of development of turbulence in relative terms of stability for the two locations are very similar. In addition, we present the first example of a profile estimated from NCEP/NCAR Reanalysis. We found that this profile presents a tendency very similar to the same averaged profile measured by the Balloon-born radiosondes.
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Meteorological profiles and optical turbulence in the free atmosphere with NCEP/NCAR data at Oukaïmeden – I. Meteorological parameters analysis and tropospheric wind regimes
Monthly Notices of the Royal Astronomical Society, 2011Co-Authors: Y. Hach, M. Sabil, A. Jabiri, A. Abahamid, Aziza Bounhir, A Ziad, Zouhair BenkhaldounAbstract:In this paper, we have used the National Centers for Environmental Prediction (NCEP)/National Centers for Atmospheric Research (NCAR) Reanalysis data base to study, first, a comparison between Balloon Sounding made at different stations with coinciding model-based meteorological analysis. The comparison allows the assessment of reliability of the analysis in the studied period and to highlight NCEP/NCAR Reanalysis as an interesting data base for site characterization. Using the same system of Reanalysis, we present, secondly, the first complete characterization of main meteorological parameters at Oukaimeden Observatory: wind speed, its direction, temperature and pressure. The statistical treatment of data will cover the years between 1990 and 2009. Monthly, seasonal and annual results are analysed. The comprehensive and reliable statistics of tropospheric wind speeds at Oukaimeden are presented. We found a clear annual periodicity of 200 mbar wind speed. This periodicity could be related to the seasonal dependence of seeing that is affected by the existence of cloud sea during the period around autumn–winter and by high wind speed regimes during spring. The connection of high- to low-altitude tropospheric winds has been explored. We found a high correlation comparable to the ones found at La Silla and La Palma sites. The local parameters in particular topography and stratocumulus formations might affect 700 mbar wind roses. Richardson numbers calculated for each month at Oukaimeden and La Palma are presented. By analysing the values, we found out that the periods and the regions of development of turbulence in relative terms of stability for the two locations are very similar. In addition, we present the first example of a profile estimated from NCEP/NCAR Reanalysis. We found that this profile presents a tendency very similar to the same averaged profile measured by the Balloon-born radiosondes.
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Meteorological parameters analysis above Oukaimeden Observatory using NCEP/NCAR data
Proceedings of SPIE, 2010Co-Authors: Y. Hach, M. Sabil, Zouhair Benkhaldoun, A. Benhida, A. Jabiri, A. Habib, A. Abahamid, Aziza BounhirAbstract:We present a characterization of meteorological parameters: Wind and direction speed, temperature, relative humidity and pressure. Data set is provided by the system of NCEP/NCAR Re-analysis. The statistical treatment of data will cover the years between 2003 and 2006 for the Observatory Oukaimeden. An analysis of monthly, seasonal, and annual results is presented. We calculated the Richardson number for each month of the year. In addition, this paper describes a comparison between Balloon-Sounding made at different stations and coincident model-based meteorological analysis. The comparison allows the assessment reliability of the analysis in studied period.
D. N. Asimakopoulos - One of the best experts on this subject based on the ideXlab platform.
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a tethered Balloon profiler system
Measurement Science and Technology, 1993Co-Authors: A T Soilemes, Costas G. Helmis, P G Papageorgas, D. N. AsimakopoulosAbstract:A microprocessor-based tethered Balloon Sounding system has been developed at the University of Athens. It can provide accurate measurements of relative pressure, dry and wet bulb temperature, wind speed and wind direction. Certain features arise from the implementation, like easy data handling, cheap and easy construction and maintenance, increased reliability and, above all, system adaptability to different experimental needs, as well as flexibility and expandability. Advantages and disadvantages of the method are discussed, as well as the implementation of the whole Sounding system.
Dirk De Muer - One of the best experts on this subject based on the ideXlab platform.
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photochemical ozone production in the convective mixed layer studied with a tethered Balloon Sounding system
Journal of Geophysical Research, 1997Co-Authors: Dirk De Muer, René Heylen, M Van Loey, G De SadelaerAbstract:In 1987, 1988, and 1990, four measuring campaigns with a tethered Balloon Sounding system were performed in a semirural area in Belgium to study the ozone distribution in the boundary layer in relation to meteorological parameters, during episodes of photochemical ozone production in the convective mixed layer. The detailed profiles of the ozone concentration between sunrise and sunset were used for a calculation of the change rate of the ozone column density in the boundary layer. These values allowed us to determine for the first time the integrated ozone production rates in the convective mixed layer, making use of a simplified form of the continuity equation of ozone mass. From all the measuring campaigns a range of integrated ozone production rates from 0 to 9 μg m−2 s−1 was found. Peak values of the ozone production rate were observed when the direct solar radiation intensity rises for the first time in the course of a day to about 400 W m−2 before noon. The upper envelope of a scatterplot of all ozone production rates as a function of the direct solar radiation shows a linear course up to about 650 W m−2. Beyond this value the intensity of direct solar radiation is no longer a rate-limiting factor in the photochemical ozone production process in the boundary layer; under these conditions the ozone production is limited by the supply rate of hydrocarbons. In general, the measured ozone production rates also show an increase with increasing ambient temperatures. At temperatures larger than 24°C the integrated net ozone production rate during the campaigns was always at least 3 μg m−2 s−1 when the direct solar radiation values were larger than 350 W m−2 . The surface ozone deposition velocity at the site of the campaigns was determined from the ozone data through an indirect method that does not require any parameterization of the vertical ozone flux; at daylight conditions an upper limit of 1.4 cm s−1 was found.
A T Soilemes - One of the best experts on this subject based on the ideXlab platform.
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a tethered Balloon profiler system
Measurement Science and Technology, 1993Co-Authors: A T Soilemes, Costas G. Helmis, P G Papageorgas, D. N. AsimakopoulosAbstract:A microprocessor-based tethered Balloon Sounding system has been developed at the University of Athens. It can provide accurate measurements of relative pressure, dry and wet bulb temperature, wind speed and wind direction. Certain features arise from the implementation, like easy data handling, cheap and easy construction and maintenance, increased reliability and, above all, system adaptability to different experimental needs, as well as flexibility and expandability. Advantages and disadvantages of the method are discussed, as well as the implementation of the whole Sounding system.
