Auflistung nach Autor:in "Jost, Dieter T."

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Aerosol climatology at the high‐alpine site Jungfraujoch, Switzerland
(Wiley, 01.08.1997) Baltensperger, Urs; Gäggeler, Heinz W.; Jost, Dieter T.; Lugauer, Matthias; Schwikowski, Margit; Weingartner, Ernest; Seibert, Petra
Continuous aerosol measurements have been performed at the high-alpine site Jungfraujoch (3450 m above sea level) since 1988 by means of an epiphaniometer. The instrument, which determines the Fuchs surface area of the aerosol particles, was operated with a time resolution of 30 min. High correlation coefficients (r>0.8) were found between the epiphaniometer signal and other aerosol parameters, which could be attributed to a rather constant size distribution of the Jungfraujoch aerosol in the accumulation range (0.1
01A - Beitrag in wissenschaftlicher Zeitschrift
Heterogeneous chemical processing of 13NO2 by monodisperse carbon aerosols at very low concentrations
(American Chemical Society, 19.09.1996) Kalberer, Markus; Tabor, K.; Ammann, Markus; Parrat, Yves; Weingartner, Ernest; Piguet, D.; Rössler, E.; Jost, Dieter T.; Türler, Andreas; Gäggeler, Heinz W.; Baltensperger, Urs
The heterogeneous reaction of NO2 with different carbon aerosol particles was investigated in situ. The NO2 was labeled with the β+-emitter 13N (half-life 10.0 min) which allowed application of NO2 at very low concentrations. The carbon aerosol was either produced by a spark discharge generator using graphite electrodes or by a brush generator resuspending commercial soot material. Monodisperse size cuts between 50- and 490-nm diameter were selected and mixed with the 13NO2. After a defined reaction time, the different reaction products were separated by means of selective traps and detected on-line by γ-spectrometry. A sticking coefficient for chemisorption of NO2 between 0.3 × 10ˉ⁴ and 4.0 × 10ˉ⁴ and a rate constant for the reduction of adsorbed NO2 to NO(g) between 4.0 × 10 ˉ⁴ and 9.4 × 10 ˉ⁴ /s were determined for both aerosols. The sticking coefficient obtained in this study in situ with aerosol particles is 2 orders of magnitudes smaller than the uptake coefficient recently reported with bulk carbon material.
01A - Beitrag in wissenschaftlicher Zeitschrift
The Jungfraujoch high‐alpine research station (3454 m) as a background clean continental site for the measurement of aerosol parameters
(Wiley, 01.03.1998) Nyeki, Stephan; Baltensperger, Urs; Colbeck, Ian; Jost, Dieter T.; Weingartner, Ernest; Gäggeler, Heinz W.
The first annual data set of climatically important aerosol parameters, measured at the Jungfraujoch (JFJ) high-alpine research station (3454 m, Switzerland) from an ongoing field campaign since July 1995, is presented. Analysis of diurnal variations in continuous measurements of the total and backward hemispheric scattering coefficients (σSP, σBSP), the absorption coefficient (σAP, from aethalometer data), condensation nuclei (CN) concentration, and epiphaniometer signal (related to surface area (S) concentration) established the diurnal period 0300 – 0900 as being representative of the free tropospheric background aerosol. The annual data set was then edited to omit (1) the period 0900–0300 (i.e., 18 hours), taken to represent possible planetary boundary layer influenced conditions and (2) in-cloud conditions using a cloud liquid-water monitor. The seasonal aerosol cycle exhibited a July maximum and a December minimum in most aerosol parameters. Typical monthly median values for the free troposphere exhibit the following seasonal maxima and minima, respectively: σSP (550 nm) ∼ 16.1 and 0.43 × 10ˉ⁶/m, σBSP (550 nm) ∼ 2.10 and 0.09 × 10ˉ⁶/m, σAP (550 nm) ∼ 10.4 and 0.76 × 10ˉ⁷/m (≈ 104 and 7.6 ng mˉ³ black carbon), CN concentration ∼ 670 and 280 cmˉ³, and epiphaniometer signal ∼ 9.26 and 0.67 counts/s (S concentration ≈24.1 and 1.7 μm2 cmˉ³). Aerosol parameters were found to be comparable in magnitude to other NOAA baseline and regional stations and suggest that a clean continental designation for the JFJ site is applicable, when removing the planetary boundary layer influenced period.
01A - Beitrag in wissenschaftlicher Zeitschrift