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- Author or Editor: Jacques Fontan x
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Abstract
Simultaneous measurements of the vertical distribution on Rn-222, Aitken nuclei and small ions have been carried out in southwest France, several hundred kilometers from the Atlantic Ocean, between ground level and 6000 m.
These measurements demonstrate the importance of radon as a tracer characterizing the continental nature of an air mass. Every one of the measurements shows an increase in the concentration of radon at altitudes in excess of 3000 m. The radon does not appear to have originated in the European continental land mass. The concentrations of Aitken nuclei, small ions and radon show a sudden variation at the upper limit of the planetary boundary layer which is due, at least in part, to the geographic location of the site at which the measurements were made.
With certain simplifying hypotheses, the mean size of atmospheric aerosols can be deduced from these measurements.
Abstract
Simultaneous measurements of the vertical distribution on Rn-222, Aitken nuclei and small ions have been carried out in southwest France, several hundred kilometers from the Atlantic Ocean, between ground level and 6000 m.
These measurements demonstrate the importance of radon as a tracer characterizing the continental nature of an air mass. Every one of the measurements shows an increase in the concentration of radon at altitudes in excess of 3000 m. The radon does not appear to have originated in the European continental land mass. The concentrations of Aitken nuclei, small ions and radon show a sudden variation at the upper limit of the planetary boundary layer which is due, at least in part, to the geographic location of the site at which the measurements were made.
With certain simplifying hypotheses, the mean size of atmospheric aerosols can be deduced from these measurements.
Abstract
This study presents a method of obtaining the quantitative intensity of vertical diffusion during periods of atmospheric stability. This method associates the continuous measurement of radon concentration at ground level and the use of a monostatic sodar. The value of “equivalent mixing height” he is calculated using the radon variation which can be related to the global exchange coefficient of the inversion layer. The sodar detects the thickness of the nocturnal inversion layer.
Both systems operated simultaneously over several months at two sites (urban and suburban). In most cases the nocturnal layer was indicated both by sodar echoes and by a large decrease of the he value. In other cases the use of sodar alone can lead to a lack of detection of stable periods which, nevertheless, are shown clearly by radon. The comparison of measurement at two sites shows a modification of nocturnal stability above the urban site. The equivalent exchange coefficients are ∼0.3 m2 s−1 (at the urban site) and 0.08 m2 s−1 (at the suburban site).
Abstract
This study presents a method of obtaining the quantitative intensity of vertical diffusion during periods of atmospheric stability. This method associates the continuous measurement of radon concentration at ground level and the use of a monostatic sodar. The value of “equivalent mixing height” he is calculated using the radon variation which can be related to the global exchange coefficient of the inversion layer. The sodar detects the thickness of the nocturnal inversion layer.
Both systems operated simultaneously over several months at two sites (urban and suburban). In most cases the nocturnal layer was indicated both by sodar echoes and by a large decrease of the he value. In other cases the use of sodar alone can lead to a lack of detection of stable periods which, nevertheless, are shown clearly by radon. The comparison of measurement at two sites shows a modification of nocturnal stability above the urban site. The equivalent exchange coefficients are ∼0.3 m2 s−1 (at the urban site) and 0.08 m2 s−1 (at the suburban site).
Abstract
Pollutants (gaseous and aerosol) contained in urban atmospheres alter radiative fluxes at the surface.Numerous radiative models have been developed, and while few experimental data are available, results areoften contradictory. We have taken measurements, over several weeks, of downward radiation (solar andinfrared) over the city of Toulouse and a rural reference site. The downward IR flux was larger at the urbansite by day and night (increase between 15 and 25 W m2). Attenuation of the incident solar radiation atthe urban site was observed (30 W m2 in the middle of the day). A radiative model enabled us to show thatthe IR flux increase is mainly due to higher air temperature associated with the urban "heat island." Theenhissivity increase due to the addition of absorbing constituents in the urban area was very weak. Theattenuation of solar radiation was due to absorption by urban aerosol. Total incoming radiation (solar+ infrared) was similar at the two sites by day and was slightly higher at the urban site during the night.
Abstract
Pollutants (gaseous and aerosol) contained in urban atmospheres alter radiative fluxes at the surface.Numerous radiative models have been developed, and while few experimental data are available, results areoften contradictory. We have taken measurements, over several weeks, of downward radiation (solar andinfrared) over the city of Toulouse and a rural reference site. The downward IR flux was larger at the urbansite by day and night (increase between 15 and 25 W m2). Attenuation of the incident solar radiation atthe urban site was observed (30 W m2 in the middle of the day). A radiative model enabled us to show thatthe IR flux increase is mainly due to higher air temperature associated with the urban "heat island." Theenhissivity increase due to the addition of absorbing constituents in the urban area was very weak. Theattenuation of solar radiation was due to absorption by urban aerosol. Total incoming radiation (solar+ infrared) was similar at the two sites by day and was slightly higher at the urban site during the night.
