O. Bujok

Forschungszentrum Jülich

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Jos Lelieveld

Cyprus Institute

C. Schiller

Forschungszentrum Jülich

D. S. McKenna

Royal College of Surgeons in Ireland

Hubertus Fischer

Oeschger Centre for Climate Change Research

Peter Hoor

Johannes Gutenberg University Mainz

Frank G. Wienhold

ETH Zurich

P. Siegmund

Royal Netherlands Meteorological Institute

Bert Scheeren

University of Groningen

J. Beuermann

Forschungszentrum Jülich

A. R. MacKenzie

University of Birmingham

Cooperative Institutions

Forschungszentrum Jülich

Max Planck Institute for Chemistry

Max Planck Society

Max Planck Institute for Nuclear Physics

Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR)

ETH Zurich

Johannes Gutenberg University Mainz

École Polytechnique Fédérale de Lausanne

Institute of Atmospheric Sciences and Climate

Utrecht University

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Tracer correlations in the northern high latitude lowermost stratosphere: Influence of cross‐tropopause mass exchange

Geophysical Research Letters (2000)

Hubertus Fischer Frank G. Wienhold Peter Hoor O. Bujok C. Schiller

We present an analysis of trace gas correlations in the lowermost stratosphere. In‐situ aircraft measurements of CO, N 2 O, NO y and O 3 , obtained during the STREAM 1997 winter campaign, have been used to investigate the role of cross‐tropopause mass exchange on tracer‐tracer relations. At altitudes several kilometers above the local tropopause, undisturbed stratospheric air was found with NO y /NO y * ratios close to unity, NO y /O 3 about 0.003–0.006 and CO mixing ratios as low as 20 ppbv (NO y * is a proxy for total reactive nitrogen derived from NO y –N 2 O relations measured in the stratosphere). Mixing of tropospheric air into the lowermost stratosphere has been identified by enhanced ratios of NO y /NO y * and NO y /O 3 , and from scatter plots of CO versus O 3 . The enhanced NO y /O 3 ratio in the lowermost stratospheric mixing zone points to a reduced efficiency of O 3 formation from aircraft NO x emissions.

Tropopause

TRACER

Mixing ratio

Trace gas

10.1029/1999gl010879

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Citations (173)

Photochemical alkene formation in seawater from dissolved organic carbon: Results from laboratory experiments

Journal of Geophysical Research Atmospheres (1998)

Monika Ratte O. Bujok Alejandro Spitzy J. Rudolph

The production mechanism of light alkenes, alkanes, and isoprene was investigated in laboratory experiments by measuring their concentrations in natural seawater as a function of spectral range, exposure time and origin, and concentration of dissolved organic carbon (DOC). The production mechanism of alkanes and of isoprene could not be clarified. Ethene and propene are produced photochemically from DOC. The relevant spectral range is UV and short‐wavelength visible light. Initial production rates (up to day 10 of exposure) were in the range of several pmol L −1 h −1 (mg DOC) −1 ; the corresponding mean quantum yields for the spectral range of 300–420 nm were about 10 −8 . Generally, the production rates and the quantum yields for ethene were about 2 times that of propene. The key factors in the total column integrated oceanic alkene production are the solar photon flux at sea surface, the penetration depth of the light into the ocean (especially the relation between different light absorbers, i.e., the extinction due to absorption of DOC), and the wavelength‐ and DOC‐dependent quantum yields. As a result of the high variability of these parameters, actual local alkene production rates for a specific oceanic region may differ considerably from the globally averaged oceanic alkene production rates. The latter were estimated to be at most 5 Mt yr −1 .

Alkene

Isoprene

Propene

10.1029/97jd03473

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Citations (84)

The temporal evolution of the ratio HNO₃/NO_y in the Arctic lower stratosphere from January to March 1997

Geophysical Research Letters (1999)

Johannes Schneider Frances H. Arnold Joachim Curtius B. Sierau Hubertus Fischer

Aircraft‐based measurements of HNO 3 , NO y , N 2 O, and O 3 have been performed in the Arctic lower stratosphere in January (POLSTAR I) and March (STREAM III) of 1997. The two projects employed different aircraft platforms. In addition, NO y and O 3 were measured using different instruments in the two campaigns. HNO 3 and NO y were found strongly correlated with correlation coefficients of 0.84 (POLSTAR I) and 0.69 (STREAM III), respectively. The fraction of HNO 3 within NO y decreased from 96% in January to 59% in March. The decrease is consistent with the lifetime of HNO 3 due to photolysis after polar sunrise. The relationship of NO y and HNO 3 with N 2 O shows that in January NO y and HNO 3 values were markedly higher than expected, which may indicate nitrification by PSC‐II particle sedimentation and evaporation. Contradictory, the ratios NO y /O 3 observed in January are only slightly elevated. In March, NO y ‐N 2 O and NO y ‐O 3 relations agree well with others reported in the literature. The difference between the NO y ‐O 3 and NO y ‐N 2 O relationships is partly explained by an observed O 3 decrease of about 30% between January and March.

Sunrise

Polar night

10.1029/1999gl900184

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Citations (24)

Unmet medical need in der Hals-Nasen-Ohren-Heilkunde: Die HNO-Ärztinnen und HNO-Ärzte sind gefordert

Laryngo-Rhino-Otologie (2022)

Orlando Guntinas‐Lichius Thomas Deitmer Jan Löhler O. Bujok

Zusammenfassung Hintergrund HNO-Ärztinnen und HNO-Ärzte sind prädestiniert dafür, den medizinischen Bedarf in der HNO-Heilkunde unter dem Dach der Deutschen Gesellschaft für Hals-Nasen-Ohren-Heilkunde, Kopf- und Hals-Chirurgie (DGHNO-KHC) wissenschaftlich zu analysieren und zu priorisieren. Diese Bedarfsanalyse ist wichtig, um gezielt Erforschung und Entwicklung medizinischer Innovationen zur besseren Versorgung von HNO-Patientinnen und HNO-Patienten auf diesen Bedarf auszurichten und entsprechende Programme zur Forschungs- und Innovationsförderung frühzeitig anzustoßen. Methoden Hiermit soll die Empfehlung ausgesprochen werden, dass die DGHNO-KHC und deren Arbeitsgemeinschaften und Arbeitsgruppen in ihren Spezialdisziplinen sich des Themas annehmen. Das Ziel ist ein umfassendes Medical Need Assessment für die HNO-Heilkunde. Die Kriterien zur Parametrisierung des medizinischen Bedarfs werden dem Konzept des unmet medical need (UMN) entnommen. Zur Priorisierung von UMN wird die Methode der multikriteriellen Entscheidungsanalyse (Multi-criteria decision analysis; MCDA) herangezogen. Empfehlung Die Arbeitsgemeinschaften und Arbeitsgruppen der DGHNO-KHC machen sich mit dem Konzept des UMN vertraut. Anschließend werden Vorschläge zu HNO-Erkrankungen mit UMN in Diagnostik und Therapie unter Beachtung der medizinischen Evidenz gesammelt. Die Vorschläge werden nach MCDA standardisiert bewertet und ein Ranking aufgestellt. Die Ergebnisse werden veröffentlicht und genutzt, um Institutionen der Forschungs- und Innovationsförderung auf den UMN in der HNO-Heilkunde aufmerksam zu machen. Diskussion Die Arbeit wird zur Weiterentwicklung des UMN-Konzepts beitragen und auch eine Grundlage schaffen können, um das Instrument des Medical Need Assessment in Deutschland zu etablieren. Die DGHNO-KHC wird über diese Arbeit als wichtiger wissenschaftlicher Motor für die Entwicklung bedarfsgetriebener medizinischer Innovationen in Deutschland wahrgenommen.

10.1055/a-1947-3108

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Citations (1)

Tropopause and hygropause variability over the equatorial Indian Ocean during February and March 1999

Journal of Geophysical Research Atmospheres (2006)

A. R. MacKenzie C. Schiller Thomas Peter A. Adriani J. Beuermann

Measurements of temperature, water vapor, total water, ozone, and cloud properties were made above the western equatorial Indian Ocean in February and March 1999. The cold‐point tropopause was at a mean pressure‐altitude of 17 km, equivalent to a potential temperature of 380 K, and had a mean temperature of 190 K. Total water mixing ratios at the hygropause varied between 1.4 and 4.1 ppmv. The mean saturation water vapor mixing ratio at the cold point was 3.0 ppmv. This does not accurately represent the mean of the measured total water mixing ratios because the air was unsaturated at the cold point for about 40% of the measurements. As well as unsaturation at the cold point, saturation was observed above the cold point on almost 30% of the profiles. In such profiles the air was saturated with respect to water ice but was free of clouds (i.e., backscatter ratio <2) at potential temperatures more than 5 K above the tropopause and hygropause. Individual profiles show a great deal of variability in the potential temperatures of the cold point and hygropause. We attribute this to short timescale and space‐scale perturbations superimposed on the seasonal cycle. There is neither a clear and consistent “setting” of the tropopause and hygropause to the same altitude by dehydration processes nor a clear and consistent separation of tropopause and hygropause by the Brewer‐Dobson circulation. Similarly, neither the tropopause nor the hygropause provides a location where conditions consistently approach those implied by a simple “tropopause freeze drying” or “stratospheric fountain” hypothesis.

Tropopause

Mixing ratio

Potential temperature

Lapse rate

Saturation (graph theory)

10.1029/2005jd006639

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Citations (27)

Journal of Atmospheric Chemistry (2001)

O. Bujok V. Tan E. Klein Ralf Nopper R. Bauer

10.1023/a:1010789715871

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Citations (22)

N₂O and O₃ relationship in the lowermost stratosphere: A diagnostic for mixing processes as represented by a three‐dimensional chemistry‐transport model

Journal of Geophysical Research Atmospheres (2000)

Ahron Bregman Jos Lelieveld M. M. P. van den Broek P. Siegmund H. Fischer

A three‐dimensional chemistry‐transport model has been used to investigate N 2 O and O 3 distributions in the lowermost stratosphere at middle and high latitudes in the Northern Hemisphere. The model results are compared with detailed in situ aircraft observations, performed in the winters of 1994–1995 and 1996–1997 and spring 1996, as part of the Stratosphere Troposphere Experiment by Aircraft Measurements (STREAM) II and III. In addition, observations performed earlier in the winter of 1997 during the Polar Stratospheric Aerosol Experiment (POLSTAR) I mission have been included. It is shown that slopes from the observed N 2 O‐O 3 relationships can be used to characterize air masses in the lowermost stratosphere and to test a global tropospheric‐stratospheric chemistry‐transport model. The calculated slopes are consistent with the general view of the N 2 O‐O 3 distribution in the lower stratosphere. However, examining the lowermost stratosphere in detail, the model occasionally calculates significantly steeper slopes than observed. The observed shallower slopes reflect the presence of polar vortex air. Depending on the strength and the persistence of the polar vortex during winter, confined polar stratospheric air masses reach the tropopause, even during late spring at midlatitudes. This is consistent with the view that stratosphere‐troposphere exchange and vortex erosion take place along isentropic surfaces from the polar reservoir.

Tropopause

Middle latitudes

Sudden stratospheric warming

10.1029/2000jd900035

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Citations (25)

High‐resolution measurements and simulation of stratospheric and tropospheric intrusions in the vicinity of the polar jet stream

Geophysical Research Letters (2002)

J. Beuermann Paul Konopka Dominik Brunner O. Bujok G. Günther

Pronounced filamentation of tropospheric and stratospheric air masses was observed on a flight in the vicinity of the polar jet stream during the STREAM 1998 campaign in Timmins, Canada. High‐spatial resolution O 3 and H 2 O measurements showed highly variable structures for the investigated region. Reconstructing high‐resolution potential vorticity (PV) fields using the reverse‐domain‐filling (RDF) technique reproduce the in‐situ O 3 measurements qualitatively. Measurements and RDF results show the intrusion of stratospheric air penetrating deep into the troposphere. The observed intrusions occur on smaller horizontal scales than generally assumed for tropopause folding events. Moreover, fine‐scale structures of tropospheric air masses being lifted up into the stratosphere could be reconstructed by the RDF technique using the tropospheric tracer specific humidity in addition to the more conventional calculations for the stratospheric tracer PV.

Tropopause

Jet stream

TRACER

10.1029/2001gl014162

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Citations (22)

The Dry Lowermost Stratosphere in the Arctic Winter: Evidence for Local Dehydration

N. Eicke O. Bujok Hubertus Fischer D. S. McKenna C. Schiller

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