52 search hits
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Quantifying transport into the lowermost stratosphere using simultaneous in-situ measurements of SF6 and CO2
(2008)
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Harald Bönisch
Andreas Engel
Joachim Curtius
Thomas Birner
Peter Hoor
- The seasonality of transport and mixing of air into the lowermost stratosphere (LMS) is studied using distributions of mean age of air and a~mass balance approach, based on in-situ observations of SF6 and CO2 during the SPURT (Spurenstofftransport in der Tropopausenregion, trace gas transport in the tropopause region) aircraft campaigns. Combining the information of the mean age of air and the water vapour distributions we demonstrate that the tropospheric air transported into the LMS above the extratropical tropopause layer (ExTL) originates predominantly from the tropical tropopause layer (TTL). The concept of our mass balance is based on simultaneous measurements of the two passive tracers and the assumption that transport into the LMS can be described by age spectra which are superposition of two different modes. Based on this concept we conclude that the stratospheric influence on LMS composition is strongest in April with tropospheric fractions (α1) below 20% and that the strongest tropospheric signatures are found in October with (α1 greater than 80%. Beyond the fractions, our mass balance concept allows to calculate the associated transit times for transport of tropospheric air from the tropics into the LMS. The shortest transit times (<0.3 years) are derived for the summer, continuously increasing up to 0.8 years by the end of spring. These findings suggest that strong quasi-horizontal mixing across the weak subtropical jet from summer to mid of autumn and the considerably shorter residual transport time-scales within the lower branch of the Brewer-Dobson circulation in summer than in winter dominates the tropospheric influence in the LMS until the beginning of next year's summer.
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Experimental characterization of the COndensation PArticle counting System for high altitude aircraft-borne application
(2008)
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Ralf Weigel
Markus Hermann
Joachim Curtius
Christiane Voigt
Saskia Walter
Thomas Böttger
Boris Lepukhov
Gennady Belyaev
Stephan Borrmann
- his study aims at a detailed characterization of an ultra-fine aerosol particle counting system for operation on board the Russian high altitude research aircraft M-55 "Geophysica" (maximum ceiling of 21 km). The COndensation PArticle counting Systems (COPAS) consists of an aerosol inlet and two dual-channel continuous flow Condensation Particle Counters (CPCs).
The aerosol inlet, adapted for COPAS measurements on board the M-55 "Geophysica", is described concerning aspiration, transmission, and transport losses. The counting efficiencies of the CPCs using the chlorofluorocarbon FC-43 as the working fluid are studied experimentally at two pressure conditions, 300 hPa and 70 hPa. Three COPAS channels are operated with different temperature differences between the saturator and the condenser block yielding smallest detectable particle sizes (dp50 – as 50% detection "cut off" diameters) of 6 nm, 11 nm, and 15 nm, respectively, at ambient pressure of 70 hPa. The fourth COPAS channel is operated with an aerosol heating line (250°C) for a determination of the non-volatile number of particles. The heating line is experimentally proven to volatilize pure H2SO4-H2O particles for a particle diameter (dp) range of 11 nm<dp<200 nm.
Additionally this study includes investigation to exclude auto-nucleation of the working fluid inside the CPCs. An instrumental inter-comparison (cross-correlation) has been performed for several measurement flights and mission flights in the Arctic and the Tropics are discussed. Finally, COPAS measurements are used for an aircraft plume crossing analysis.
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Applicability of condensation particle counters to measure atmospheric clusters
(2008)
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Mikko Sipilä
Katrianne Lehtipalo
Markku Kulmala
Tuukka Petäjä
Heikki Junninen
Pasi Aalto
Hanna Manninen
E. Vartianinen
Ilona Riipinen
Ella-Maria Kyrö
Joachim Curtius
Andreas Kürten
Stephan Borrmann
Colin D. O'Dowd
- The ambient and laboratory molecular and ion clusters were investigated. Here we present data on the ambient concentrations of both charged and uncharged molecular clusters as well as the performance of a pulse height condensation particle counter (PH-CPC) and an expansion condensation particle counter (E-CPC). The ambient molecular cluster concentrations were measured using both instruments, and they were deployed in conjunction with ion spectrometers and other aerosol instruments in Hyytiälä, Finland at the SMEAR II station during 1 March to 30 June 2007. The observed cluster concentrations varied and were from ca. 1000 to 100 000 cm−3. Both instruments showed similar concentrations. The average size of detected clusters was approximately 1.8 nm. As the atmospheric measurements at sub 2-nm particles and molecular clusters are a challenging task, and we were most likely unable to detect the smallest clusters, the reported concentrations are our best estimates for minimum cluster concentrations in boreal forest environment.
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Fachspezifischer Anhang zur SPoL (Teil III): Studienfach Erdkunde im Studiengang L3 (Stand:11. Februar 2008)
(2008)
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Fachspezifischer Anhang zur SPoL (Teil III): Studienfach Erdkunde im Studiengang L 2 und L 5
(2008)
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Ordnung des Fachbereichs Geowissenschaften/Geographie an der Johann Wolfgang Goethe-Universität für den Masterstudiengang Geowissenschaften mit dem Abschluss "Master of Science Geowissenschaften mit Schwerpunkt Geologie/Paläontologie" oder "Master of Science Geowissenschaften mit Schwerpunkt Geophysik" oder "Master of Science Geowissenschaften mit Schwerpunkt Mineralogie" : genehmigt durch das Hessische Ministerium für Wissenschaft und Kunst mit Erlass vom 05.07.2007, Az.: III 1.3 422/11/10.010-(0003)
(2008)
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Ordnung des Fachbereichs Geowissenschaften/Geographie an der Johann Wolfgang Goethe-Universität für den Bachelorstudiengang Geowissenschaften mit dem Abschluss "Bachelor of Science" : genehmigt durch das Hessische Ministerium für Wissenschaft und Kunst mit Erlass vom 05.07.2007, Az.: III 1.3 422/11/10.010-(0003)
(2008)
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Ordnung des Fachbereichs Geowissenschaften/Geographie an der Johann Wolfgang Goethe-Universität für den Bachelorstudiengang Geographie mit den Abschlüssen "Bachelor of Arts" oder "Bachelor of Science" vom 19. Mai 2008 : genehmigt vom Präsidium der Johann Wolfgang Goethe- Universität Frankfurt am 16.09.2008;
(2008)
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Ordnung des Fachbereichs Geowissenschaften/Geographie an der Johann Wolfgang Goethe-Universität für das Nebenfach Geographie in einem Bachelorstudiengang vom 5. Februar 2007 : genehmigt vom Präsidium der Johann Wolfgang Goethe- Universität Frankfurt am 16.09.2008
(2008)
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Value of river discharge data for global-scale hydrological modeling
(2008)
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Martin Hunger
Petra Döll
- This paper investigates the value of observed river discharge data for global-scale hydrological modeling of a number of flow characteristics that are e.g. required for assessing water resources, flood risk and habitat alteration of aquatic ecosystems. An improved version of the WaterGAP Global Hydrology Model (WGHM) was tuned against measured discharge using either the 724-station dataset (V1) against which former model versions were tuned or an extended dataset (V2) of 1235 stations. WGHM is tuned by adjusting one model parameter (γ) that affects runoff generation from land areas in order to fit simulated and observed long-term average discharge at tuning stations. In basins where γ does not suffice to tune the model, two correction factors are applied successively: the areal correction factor corrects local runoff in a basin and the station correction factor adjusts discharge directly the gauge. Using station correction is unfavorable, as it makes discharge discontinuous at the gauge and inconsistent with runoff in the upstream basin. The study results are as follows. (1) Comparing V2 to V1, the global land area covered by tuning basins increases by 5% and the area where the model can be tuned by only adjusting γ increases by 8%. However, the area where a station correction factor (and not only an areal correction factor) has to be applied more than doubles. (2) The value of additional discharge information for representing the spatial distribution of long-term average discharge (and thus renewable water resources) with WGHM is high, particularly for river basins outside of the V1 tuning area and in regions where the refined dataset provides a significant subdivision of formerly extended tuning basins (average V2 basin size less than half the V1 basin size). If the additional discharge information were not used for tuning, simulated long-term average discharge would differ from the observed one by a factor of, on average, 1.8 in the formerly untuned basins and 1.3 in the subdivided basins. The benefits tend to be higher in semi-arid and snow-dominated regions where the model is less reliable than in humid areas and refined tuning compensates for uncertainties with regard to climate input data and for specific processes of the water cycle that cannot be represented yet by WGHM. Regarding other flow characteristics like low flow, inter-annual variability and seasonality, the deviation between simulated and observed values also decreases significantly, which, however, is mainly due to the better representation of average discharge but not of variability. (3) The choice of the optimal sub-basin size for tuning depends on the modeling purpose. While basins over 60 000 km2 are performing best, improvements in V2 model performance are strongest in small basins between 9000 and 20 000 km2, which is primarily related to a low level of V1 performance. Increasing the density of tuning stations provides a better spatial representation of discharge, but it also decreases model consistency, as almost half of the basins below 20 000 km2 require station correction.
