Use of A-train satellite observations (CALIPSO–PARASOL) to evaluate tropical cloud properties in the LMDZ5 GCM     

D. Konsta  J.-L. Dufresne  H. Chepfer  A. Idelkadi  G. Cesana 《Climate Dynamics》2016,47(3-4):1263-1284

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Interpreting the inter-model spread in regional precipitation projections in the tropics: role of surface evaporation and cloud radiative effects     

Boutheina Oueslati  Sandrine Bony  Camille Risi  Jean-Louis Dufresne 《Climate Dynamics》2016,47(9-10):2801-2815

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The dependence of organohalogen compound concentrations on herring age and size in the Bothnian Sea, northern Baltic     

Parmanne R  Hallikainen A  Isosaari P  Kiviranta H  Koistinen J  Laine O  Rantakokko P  Vuorinen PJ  Vartiainen T 《Marine pollution bulletin》2006,52(2):149-161

The concentrations and composition profiles of polychlorinated dibenzo-p-dioxins and dibenzofurans, polychlorinated biphenyls, polybrominated diphenyl ethers and polychlorinated naphthalenes were determined in herring individuals collected from the commercial catches of the Bothnian Sea, northern Baltic. The median age of herring was 5.0 years and in the muscle the median toxic equivalent concentration of PCDD/Fs was 5.6 WHO(PCDD/F)-TEQ pg/g fresh weight (fw) and that of PCBs 2.7 WHO(PCB)-TEQ pg/g fw. The median sum concentration of PBDEs was 1.4 ng/g fw and that of PCNs 0.1 ng/g fw. Differences in age-dependent accumulation between the organohalogen groups and individual congeners were major. In the Bothnian Sea the content of organohalogen compounds in herring is obviously elevated due to the availability and large proportion of Mysis crustaceans in their diet. More intensive fishing could reduce the concentrations of organohalogens, including the abundant, accumulative and toxic 2,3,4,7,8-PeCDF congener in the Baltic herring catch.  相似文献   

Single-crystal polarized FTIR spectroscopy and neutron diffraction refinement of cancrinite     

Giancarlo Della Ventura  G. Diego Gatta  Gunter J. Redhammer  Fabio Bellatreccia  Anja Loose  Gian Carlo Parodi 《Physics and Chemistry of Minerals》2009,36(4):193-206

We relate a single-crystal FTIR (Fourier transform infrared) and neutron diffraction study of two natural cancrinites. The structural refinements show that the oxygen site of the H₂O molecule lies off the triad axis. The water molecule is almost symmetric and slightly tilted from the (0001) plane. It is involved in bifurcated hydrogen bridges, with Ow···O donor–acceptor distances >2.7 Å. The FTIR spectra show two main absorptions. The first at 3,602 cm^?1 is polarized for E ⊥ c and is assigned to the ν₃ mode. The second, at 3,531 cm^?1, is also polarized for E ⊥ c and is assigned to ν₁ mode. A weak component at 4,108 cm^?1 could possibly indicate the presence of additional OH groups in the structure of cancrinite. Several overlapping bands in the 1,300–1,500 cm^?1 range are strongly polarized for E ⊥ c, and are assigned to the vibrations of the CO₃ group.  相似文献   

Impacts of greenhouse gases and aerosol direct and indirect effects on clouds and radiation in atmospheric GCM simulations of the 1930–1989 period     

Johannes Quaas  Olivier Boucher  Jean-Louis Dufresne  Hervé Le Treut 《Climate Dynamics》2004,23(7-8):779-789

Among anthropogenic perturbations of the Earths atmosphere, greenhouse gases and aerosols are considered to have a major impact on the energy budget through their impact on radiative fluxes. We use three ensembles of simulations with the LMDZ general circulation model to investigate the radiative impacts of five species of greenhouse gases (CO₂, CH₄, N₂O, CFC-11 and CFC-12) and sulfate aerosols for the period 1930–1989. Since our focus is on the atmospheric changes in clouds and radiation from greenhouse gases and aerosols, we prescribed sea-surface temperatures in these simulations. Besides the direct impact on radiation through the greenhouse effect and scattering of sunlight by aerosols, strong radiative impacts of both perturbations through changes in cloudiness are analysed. The increase in greenhouse gas concentration leads to a reduction of clouds at all atmospheric levels, thus decreasing the total greenhouse effect in the longwave spectrum and increasing absorption of solar radiation by reduction of cloud albedo. Increasing anthropogenic aerosol burden results in a decrease in high-level cloud cover through a cooling of the atmosphere, and an increase in the low-level cloud cover through the second aerosol indirect effect. The trend in low-level cloud lifetime due to aerosols is quantified to 0.5 min day^–1 decade^–1 for the simulation period. The different changes in high (decrease) and low-level (increase) cloudiness due to the response of cloud processes to aerosols impact shortwave radiation in a contrariwise manner, and the net effect is slightly positive. The total aerosol effect including the aerosol direct and first indirect effects remains strongly negative.  相似文献   

Competition between pelagic and benthic microalgae for phosphorus and light   总被引：2，自引：0，他引：2  

Sabine Flöder  Anja Combüchen  Annika Pasternak  Helmut Hillebrand 《Aquatic Sciences - Research Across Boundaries》2006,68(4):425-433

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Optically stimulated luminescence dating of sublittoral and intertidal sediments from Dubai, UAE: Radioactive disequilibria in the uranium decay series   总被引：1，自引：0，他引：1  

Anja Zander  Detlev Degering  Frank Preusser  Haino Uwe Kasper  Helmut Brückner 《Quaternary Geochronology》2007,2(1-4):123-128

Shallow marine and intertidal shell rich sediments from the low coastal plain of Dubai were dated by optically stimulated luminescence. Combined high-resolution gamma spectrometry and ICP–MS analyses revealed significant disequilibria in the ²³⁸U decay series. Time dependent dose rates were modelled for two scenarios including a closed system and an open system with linear U and Ra uptake. OSL ages that were calculated using the linear uptake model are in good agreement with archaeological evidence and radiocarbon datings on shells and wood. The presented results illustrate that luminescence-dating techniques are suitable to set up a chronostratigraphic frame for calcareous coastal environments if an appropriate model is applied to consider the influence of radioactive disequilibria and time dependent dose rates. A comprehensive radionuclide analysis of the sediments is thought necessary to perform geochemically supported dose rate simulations.  相似文献   

Geodetic observations of ice flow velocities over the southern part of subglacial Lake Vostok, Antarctica, and their glaciological implications   总被引：1，自引：0，他引：1  

Jens Wendt  Reinhard Dietrich  Mathias Fritsche  Anja Wendt  Alexander Yuskevich  rey Kokhanov  Anton Senatorov  Valery Lukin  Kazuo Shibuya  Koichiro Doi 《Geophysical Journal International》2006,166(3):991-998

In the austral summer seasons 2001/02 and 2002/03, Global Positioning System (GPS) data were collected in the vicinity of Vostok Station to determine ice flow velocities over Lake Vostok. Ten GPS sites are located within a radius of 30 km around Vostok Station on floating ice as well as on grounded ice to the east and to the west of the lake. Additionally, a local deformation network around the ice core drilling site 5G-1 was installed.
The derived ice flow velocity for Vostok Station is  2.00 m a⁻¹± 0.01 m a⁻¹  . Along the flowline of Vostok Station an extension rate of about 10⁻⁵ a⁻¹ (equivalent to 1 cm km⁻¹ a⁻¹) was determined. This significant velocity gradient results in a new estimate of 28 700 years for the transit time of an ice particle along the Vostok flowline from the bedrock ridge in the southwest of the lake to the eastern shoreline. With these lower velocities compared to earlier studies and, hence, larger transit times the basal accretion rate is estimated to be 4 mm a⁻¹ along a portion of the Vostok flowline. An assessment of the local accretion rate at Vostok Station using the observed geodetic quantities yields an accretion rate in the same order of magnitude. Furthermore, the comparison of our geodetic observations with results inferred from ice-penetrating radar data indicates that the ice flow may not have changed significantly for several thousand years.  相似文献   

Long-wave radiative analysis of cloudy scattering atmospheres using a net exchange formulation     

V. Eymet  J. L. Dufresne  P. Ricchiazzi  R. Fournier  S. Blanco 《Atmospheric Research》2004,72(1-4):239

The Net Exchange Formulation (NEF) is an alternative to the usual radiative transfer equation. It was proposed in 1967 by Green [Q. J. R. Meteorol. Soc. 93 (1967) 371] for atmospheric sciences and by Hottel [H.C. Hottel, A.F. Sarofim. Radiative Transfer McGraw Hill, New York, 1967] for engineering sciences. Until now, the NEF has been used only in a very few cases for atmospheric studies. Recently we have developed a long-wave radiative code based on this formulation for a GCM of the Mars planet. Here, we will present results for the Earth atmosphere, obtained with a Monte Carlo Method based on the NEF. In this method, fluxes are not addressed any more. The basic variables are the net exchange rates (NER) between each pair of atmospheric layer (i, j), i.e. the radiative power emitted by i and absorbed by j minus the radiative power emitted by j and absorbed by i. The graphical representation of the NER matrix highlights the radiative exchanges that dominate the radiative budget of the atmosphere and allows one to have a very good insight of the radiative exchanges. Results will be presented for clear sky atmospheres with Mid-Latitude Summer and Sub-Arctic Winter temperature profiles, and for the same atmospheres with three different types of clouds. The effect of scattering on long-wave radiative exchanges will also be analysed.  相似文献   

Field and Laboratory Exposures of Two Moss Species to Low Level Metal Pollution     

Anja H. Tremper  M. Agneta  S. Burton  David E. B. Higgs 《Journal of Atmospheric Chemistry》2004,49(1-3):111-120

Moss transplants of the species Rhytidiadelphus squarrosus and Pleurozium schreberi were used as active biomonitoring organisms as a part of a monitoring study to assess the impact of metals associated with ambient particles on mosses at roadsides.The moss samples were exposed at a semi-urban and roadside site for 3 months for subsequent analysis of metal concentration (Cu, Pb and Zn). This field experiment was carried out to investigate the accumulation of the metals over a period of 0, 4, 8 and 12 weeks at the two sites. The metal concentration in the moss samples generally increased with the length of exposure and was higher at the roadside site. The two species, however, showed slightly different accumulation patterns. In addition to the metal analysis chlorophyll concentrations were analysed as a measure of stress response in the moss samples of the above mentioned field exposures. The chlorophyll concentrations of exposed mosses showed no or only weak correlations to the concentration of the three metals measured in the moss, which suggests that other conditions have a greater influence on the chlorophyll concentration.The effect of a single metal on the moss was studied in laboratory experiments exposing R. squarrosus to the metals copper, lead and zinc at concentrations based on the above field data. At the concentrations used there was a significant reduction in the chlorophyll a concentration after exposure to copper.  相似文献