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  • 1
    ISSN: 1432-1041
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract We have used a ruby Lidar to study the space and time variations of atmospheric aerosols on a horizontal level above a town site. It has allowed us to locate the main sources of industrial pollution and to evaluate the amplitude of retrodiffusion signals due to the town activity. We have demonstrated the influence of the winds whose speed is higher than 3 m/s. We have observed that at any particular place in the town the ratio Am/Amo varied from 1 to 14, this radio characterizing the concentration in pollutants above a place in the town (Am is the amplitude of the retrodiffusion Lidar signal, Amo is the echo lidar amplitude characterizing the average noise of the urban site).
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 197 (1963), S. 583-584 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] In previous papers1"2, an apparatus for measuring the natural radioactivity of the air was described. We have examined the meteorological conditions by referring to the daily weather information of the Meteorologie Nationale, and the local data obtained at the K point, especially the wind direction ...
    Type of Medium: Electronic Resource
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  • 4
    Publication Date: 2011-08-24
    Description: Results of ozone and Aitken condensation nuclei measurements made over the rain forest in equatorial Africa during February 12-25, 1988 are presented. The results indicate the presence of a layer between 1 and 4 km altitude where these species are strongly enriched. Based on information derived from simultaneous measurements of other chemical and meteorological parameters, satellite imagery, and trajectory calculations, this enrichment is attributed to emissions from biomass burning in sub-Saharan Africa, from which ozone is formed by photochemical reactions.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 97; D6, A
    Format: text
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  • 5
    ISSN: 0029-554X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Physics
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-1472
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract For a ground-level continuous release of a trace substance like 222Rn, for which the vertical profile of concentrations is exponential, a quantity, ‘equivalent mixing height’ h, is defined in this paper in the following way. If the substance were to be redistributed uniformly through a layer such that the concentration were to be equal to that at the surface, then the top of the layer would be h. Relative values of h can be obtained from surface measurements of Radon concentrations, but absolute values require estimates of the vertical fluxes of Radon. A comparison is given of the estimates of h obtained from surface measurements with estimates derived from the vertical profile of Radon from the surface to 100 m. Practical methods are proposed for estimating the surface flux of Rn.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-1472
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Analysis of turbulent transfer inside a vegetative canopy can be realized by means of several methods. In our case, we have used principally the aerodynamic and the thoron methods. The thoron diffusivity profiles show an important distortion in the middle zone of the canopy, below the maximum of leaf area density. This distortion is associated with a maximum source of sensible heat flux at these levels, which partially invalidates the aerodynamic approach.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-1472
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Description / Table of Contents: Abstract Continuous measurements of the concentrations of radon and thorium B have been carried out at 3 levels (1.5, 30 and 100 m) during a period of 2 yr (from October 1966 to October 1968) at the site of the future airport of Paris, at Roissy-en-France; at the same time, standard meteorological elements have been measured at the station by the ‘Météorologie Nationale’ and the vertical gradients (wind and temperature profiles in the first 100 m) by J. Saissac. The work has been undertaken in order to determine the vertical exchange of matter near the ground. The computation of the exchange coefficients has been carried out by using the standard diffusion equation (K theory). The results in the literature as well as statistical analysis of our data lead us to believe that the flux of Rn and ThB at the ground can be considered as horizontally homogeneous in the neighbourhood of the measurement site (the soil is geologically homogeneous over a large area). The differential equation is thus simplified, containing only one space parameter (z), and timet. In this paper we describe the principal computation methods used for determining the exchange coefficients from the measurement of the vertical gradients of tracers. In order to illustrate the approximation errors and fields of applicability of different methods, we have applied them to the data provided from a numerical integration of the diffusion equation, in which one can introduce any profile of diffusivity. We show that during stable periods, the value of the flux of Rn or ThB can be determined forz = 0. Generally, during daylight hours when the motion near the ground is strongly turbulent, the vertical gradient of concentration is not measurable with sufficient accuracy. The daytime diffusion coefficient is therefore not computed by the general methods presented above. This deficiency can be overcome by assuming that the ratio between the mean concentration observed during these periods and the value of the flux at ground level are characteristic of the whole mixing layer. The values of the exchange coefficients obtained by this method are included and range from 5 to 30 m2s-1. The application of the proposed methods to the experimental results has been made for two atmospheric states. Firstly, we have used a simplified method (stationary state) which is applied to the whole experimental data set. We present the diurnal variation, the most probable value of the diffusion coefficients and the seasonal evolution. The values obtained from Rn and ThB measurements have been compared.
    Notes: Résumé Le radon (Rn86 222) et les descendants du thoron (ThB ou Pb82 212) sont utilisés comme traceurs pour l'étude des échanges verticaux de matière. Diverses méthodes permettant le calcul des coefficients de diffusion sont présentées soit dans l'hypothèse simplificatrice du régime stationnaire, soit dans le cas plus général du régime dépendant du temps. L'application de ces méthodes au calcul des coefficients de diffusion sur des données fournies à partir d'un modèle de simulation numérique permet de préciser le degré d'approximation représenté par les diverses hypothèses simplificatrices. Les méthodes de calcul présentées sont appliquées aux mesures expérimentales du radon et du ThB. Ces mesures ont été réalisées de manière continue durant deux ans en trois points de mesures, entre 0 et 100 m de hauteur. Une statistique est présentée sur la variation diurne des échanges et la variation saisonnière de cette variation diurne, ainsi qu'un exemple particulier du traitement des données en régime dépendant du temps.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1573-0662
    Keywords: biomass burning ; diurnal estimation ; fire propagation model (BEHAVE) ; Central African Republic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Experimental studies and mesoscale modeling of atmospheric chemistry require a good knowledge of the sources of the atmospheric constituent, at a temporal scale of about one hour and at a spatial scale corresponding to the model grid. A combined remote sensing/modeling approach for the estimation of the diurnal distribution of the amount of biomass burning in Central African Republic (C.A.R.) savanna fires is proposed. The fire propagation model (BEHAVE) developed by Rothermel was adapted to the fuel characteristics encountered in C.A.R. Ground and airborne measurements with satellite images (NOAA/AVHRR) were used to predict an accurate estimate of the burnt biomass. This combination allows the calculation of the distribution of the number of fires during the day providing an evaluation of the instantaneous fluxes of the compounds emitted in the atmosphere by these fires.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1573-0662
    Keywords: biomass burning ; West African savanna ; satellite data ; multispectral method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Remote sensing measurements provide a vauable means of determining the extent of burning areas and of estimating the overall distribution of pollutant sources (identified from experimental studies) in time and space. This distribution has to be taken into account in the boundary conditions of chemistry atmospheric models. Recent methods developed for the remote sensing of active fires in tropical or temperated forest zones, have been found to be completely inadequate for fire detection on West African savannas. In order to accurately estimate the active fire distribution in the function of different sorts of West African savannas (Sahelian, Sudanian and Guinean) and forests, a multispectral methodology has been developed based on NOAA/11-AVHRR satellite data, with the purpose of eliminating as much as possible the problems related to large surface heterogeneity, confusion and bias, produced by clouds, smoke, haze, background emissivities, etc. Unlike other methods, the results show that the multispectral method, in spite of its selectivity, provides realistic results, and does not under- or over-estimate the number of fires that can be sensed by the satellite. Consequently, this methodology is more appropriate than the simplest ones for a systematic sensing of this phenomenon.
    Type of Medium: Electronic Resource
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