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  • 1
    Publication Date: 2012-01-24
    Description: The decadal solar cycle modulation of Earth's radiative forcing via ionization of the atmosphere by galactic cosmic rays, aerosol formation from the gas phase, and the response of clouds to aerosol is quantified for the first time with a climate model that represents and couples the relevant processes. Simulations are conducted for solar maximum and minimum conditions, with present-day anthropogenic aerosol and aerosol precursor gas emissions, and contemporary large-scale meteorology. The solar cycle signal appears in atmospheric ionization, aerosol formation from the gas phase, aerosol concentrations, aerosol optical depth, and in cloud properties, and is most pronounced at mid- and high latitudes. The resulting solar cycle modulation of Earth's radiative forcing exhibits a distinct hemispheric asymmetry, with peak values of −0.14 W m−2 in the southern and −0.06 W m−2 in the northern mid-latitudes. Globally and annually averaged, the solar cycle modulation of Earth's radiative forcing, arising from the increase in atmospheric ionization by galactic cosmic rays from solar maximum to minimum, via charged nucleation of aerosol, the direct aerosol effect, and the cloud albedo effect, amounts to −0.05 W m−2. A limited relevance of this variation for the Earth's atmosphere and climate can be inferred, given that Earth's radiative forcing changes by −0.24 W m−2 from solar maximum to minimum because of a decrease in total solar irradiance.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
    Publication Date: 2002-10-26
    Description: The Mediterranean Intensive Oxidant Study, performed in the summer of 2001, uncovered air pollution layers from the surface to an altitude of 15 kilometers. In the boundary layer, air pollution standards are exceeded throughout the region, caused by West and East European pollution from the north. Aerosol particles also reduce solar radiation penetration to the surface, which can suppress precipitation. In the middle troposphere, Asian and to a lesser extent North American pollution is transported from the west. Additional Asian pollution from the east, transported from the monsoon in the upper troposphere, crosses the Mediterranean tropopause, which pollutes the lower stratosphere at middle latitudes.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lelieveld, J -- Berresheim, H -- Borrmann, S -- Crutzen, P J -- Dentener, F J -- Fischer, H -- Feichter, J -- Flatau, P J -- Heland, J -- Holzinger, R -- Korrmann, R -- Lawrence, M G -- Levin, Z -- Markowicz, K M -- Mihalopoulos, N -- Minikin, A -- Ramanathan, V -- De Reus, M -- Roelofs, G J -- Scheeren, H A -- Sciare, J -- Schlager, H -- Schultz, M -- Siegmund, P -- Steil, B -- Stephanou, E G -- Stier, P -- Traub, M -- Warneke, C -- Williams, J -- Ziereis, H -- New York, N.Y. -- Science. 2002 Oct 25;298(5594):794-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Max Planck Institute for Chemistry, Post Office Box 3060, 55020 Mainz, Germany. lelieveld@mpch-mainz.mpg.de〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/12399583" target="_blank"〉PubMed〈/a〉
    Keywords: Aerosols ; *Air Pollutants ; *Air Pollution ; Asia ; Atmosphere ; *Carbon Monoxide ; Climate ; Europe ; Mediterranean Region ; North America ; Ozone ; Weather
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 3
    Publication Date: 2013-04-12
    Description: [1]  This study investigates changes in extreme temperature and precipitation events under different future scenarios of anthropogenic aerosol emissions (i.e., SO 2 , black and organic carbon) simulated with the ECHAM5-HAM global climate model with focus on Europe. The simulations include a maximum feasible aerosol reduction (MFR) scenario, a CLE mod scenario where Europe implements the MFR scenario, but the rest of the world follows the current legislation scenario and a greenhouse gas scenario following SRES B2. Strongest changes relative to the year 2000 are projected for the MFR scenario in which the global aerosol reduction greatly enforces the general warming effect due to greenhouse gases and results in significant increases of temperature and precipitation extremes in Europe. Regional warming effects can also be identified from aerosol reductions under the CLE mod scenario. This becomes most obvious in the increase of the hottest summer day-time temperatures in Northern Europe.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 4
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The response of the global climate system to smoke from burning oil wells in Kuwait is investigated in a series of numerical experiments using a coupled atmosphere–ocean general circulation model with an interactive soot transport model and extended radiation scheme. The results show a ...
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Climate dynamics 13 (1997), S. 235-246 
    ISSN: 1432-0894
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract.  The atmospheric general circulation model ECHAM-4 is coupled to a chemistry model to calculate sulfate mass distribution and the radiative forcing due to sulfate aerosol particles. The model simulates the main components of the hydrological cycle and, hence, it allows an explicit treatment of cloud transformation processes and precipitation scavenging. Two experiments are performed, one with pre-industrial and one with present-day sulfur emissions. In the pre-industrial emission scenario SO2 is oxidized faster to sulfate and the in-cloud oxidation via the reaction with ozone is more important than in the present-day scenario. The atmospheric sulfate mass due to anthropogenic emissions is estimated as 0.38 Tg sulfur. The radiative forcing due to anthropogenic sulfate aerosols is calculated diagnostically. The backscattering of shortwave radiation (direct effect) as well as the impact of sulfate aerosols on the cloud albedo (indirect effect) is estimated. The model predicts a direct forcing of −0.35 W m-2 and an indirect forcing of −0.76 W m-2. Over the continents of the Northern Hemisphere the direct forcing amounts to −0.64 W m-2. The geographical distribution of the direct and indirect effect is very different. Whereas the direct forcing is strongest over highly polluted continental regions, the indirect forcing over sea exceeds that over land. It is shown that forcing estimates based on monthly averages rather than on instantaneous sulfate pattern overestimate the indirect effect but have little effect on the direct forcing.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Meteorology and atmospheric physics 33 (1984), S. 101-116 
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Description / Table of Contents: Summary Looking at the fields of divergence, vorticity and vertical motion, the formation and dynamics of cut-off lows has been studied and compared with the life cycle of an extratropical cyclone. In order to illustrate the energetics of cut-off lows, some terms of Lorenz's energy flow diagram have been computed. The essential difference between the formation of a cut-off low and an extratropical cyclone lies in the distribution of divergence and convergence at 300 hPa. With cut-off lows, the dominating feature is convergence aloft, above the cold air, whereas with extratropical cyclones it is divergence aloft, above the warm air. Accordingly, in a cut-off low sinking motion in the cold air predominates initially, in a cyclone, however, rising motion where the wave develops in the warm air. After the cut-off process has been completed, a region of rising motion develops along its eastern half. Initially, therefore, we have a thermally direct circulation predominating, with rigorous conversion of available potential into kinetic energy. In a later stage, however, an indirect circulation is gradually set up, with relatively cold air ascending in the eastern half of the cut-off low. As a consequence, the cut-off low is being dissolved.
    Notes: Zusammenfassung Anhand von Feldern der Divergenz, der Vorticity und der Vertikalbewegung wurde die Genese und Dynamik von Kalfufttropfen untersucht und mit der Entwicklung einer außertropischen Zyklone verglichen. Um Einblick in die Energetik von Kaltlufttropfen zu erhalten, wurden einige Terme aus dem Lorenzschen Energieflußdiagramm berechnet. Der wesentliche Unterschied zwischen der Genese eines Kaltlufttropfens und einer außertropischen Zyklone liegt in der Verteilung der Vergenzen in 300 hPa. Bei Kaltlufttropfen dominiert in der Höhe über der Kaltluft Konvergenz, bei der außertropischen Zyklone hingegen Divergenz über der Warmluft. Entsprechend überwiegt anfänglich beim Kaltlufttropfen Absinken in der Kaltluft, bei der Zyklogenese hingegen Aufsteigen am Ort der Wellenbildung innerhalb der Warmluft. Nach erfolgter Abschnürung des Kaltlufttropfens bildet sich in seiner östlichen Hälfte ein Aufsteigegebiet aus. Während also zuerst direkte Zirkulation vorherrscht mit kräftiger Umwandlung von verfügbarer potentieller in kinetische Energie, setzt allmählich indirekte Zirkulation durch Aufsteigen von relativ kalter Luft in der östlichen Hälfte des Tropfens ein, was in weiterer Folge zur Auflösung des Kaltlufttropfens führt.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied climatology 62 (1999), S. 85-108 
    ISSN: 1434-4483
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Summary  We study the three-dimensional transport of Mt. Pinatubo volcanic cloud with the climate model ECHAM4. In order to obtain model results comparable with observations a Newtonian relaxation technique was applied, which forces prognostic model variables towards the observations. A comparison of the simulated aerosol distribution with satellite data reveals good agreement for the first months after the eruption. The model, however, is unable to simulate the tropical aerosol maximum in 1992 and also overestimates the vertical downward and northward transport of aerosols. Substantial improvement was achieved with the introduction of reduced advective vertical transport through the 380 K isentropic layer. Heating rates and top of the atmosphere fluxes, which were calculated online for the first half year after the eruption, are in the observed range. A comparison of Pinatubo simulations between three different vertical ECHAM4 versions (ECHAM4 L19, ECHAM4 L39, MA/ECHAM4) indicates that a vertical resolution of ≈ 700 m in the tropopause region is sufficient to realistically reduce the vertical transport through the tropopause. Consideration of the upper branch of the Brewer Dobson circulation in the MA/ECHAM4 model improves the geographical distribution of the volcanic cloud. The application of a relaxation technique can further reduce major shortcomings of stratospheric simulations with the standard climate model. There remain, however some critical points in the global transport characteristics in all three models which are not fully understood.
    Type of Medium: Electronic Resource
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  • 8
  • 9
    Publication Date: 2009-09-01
    Print ISSN: 1951-6355
    Electronic ISSN: 1951-6401
    Topics: Physics
    Published by Springer
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  • 10
    Publication Date: 1984-06-01
    Print ISSN: 0177-7971
    Electronic ISSN: 1436-5065
    Topics: Geography , Physics
    Published by Springer
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