Investigation of the stratospheric inorganic bromine budget for 1996-2000: balloon-borne measurements and model comparisons

Inhaltsverzeichnis (Table of Contents)

• Introduction
• Halogen species and their importance in atmospheric chemistry
  • Stratospheric Ozone
  • Tropospheric Ozone
  • Stratospheric gas phase chemistry related to ozone
    • Chapman Chemistry
    • Catalytic Cycles
    • Nitrogen chemistry in the stratosphere
    • Halogen chemistry in the stratosphere
  • Heterogeneous chemistry on PSCs leading to the Ozone Hole
    • Heterogeneous chemistry on sulphate aerosols
  • Fundamental Stratospheric Dynamics
  • The atmospheric halogen budget
• Measurement Technique : Direct Sunlight Balloon Borne DOAS (Di erential Optical Absorption Spectroscopy)
  • Solar Radiation and the Solar Spectrum
    • Interaction of light with matter
    • Lambert-Beer's Law - Optical Absorption Spectroscopy
  • Di erential Optical Absorption Spectroscopy (DOAS)
  • The DOAS double spectrograph for balloon-borne measurements
    • Noise sources of the measurements
  • The LPMA/DOAS balloon payload
    • The behaviour of the DOAS spectrograph during the balloon ights and its impact on the BrO evaluation
    • The BrO DOAS evaluation
    • The OC lO DOAS evaluation
  • Determination of the SCD o set in the Fraunhofer reference - Langley Plot
  • Summary of the error sources of the bromine oxide SCD measurements
  • Pro le Retrieval
    • Raytracing
    • AMF matrix inversion
    • Errors of the inversion technique
    • Di erential Onion Peeling technique
  • Modelling of SCDs
• Results and Discussion of the LPMA/DOAS balloon ights
  • The sunset ight at León on November 23, 1996
    • BrO pro le and SCD model comparison
    • OC lO pro le and SCD model comparison
  • The sunset ight at Kiruna on February 14, 1997
    • BrO pro le and SCD model comparison
    • OC lO pro le model comparison
    • O3 pro le model comparison
    • NO2 pro le model comparison
    • Summary of the model comparison
  • The sunrise ight at Gap on June 20, 1997
    • BrO pro le and SCD model comparison
  • The sunset ight at León on March 19, 1998
    • BrO pro le and VCD comparison with GOME
  • The sunset and sunrise ight at Kiruna on August 19/20, 1998
    • BrO pro le and SCD model comparison for the sunset
    • BrO SCD model comparison for the sunrise
  • The sunset ight at Kiruna on February 10, 1999
    • BrO pro le and SCD model comparison
    • OC lO pro le and SCD model comparison
  • The sunrise ight at Gap on June 25, 1999
  • The sunset ight at Kiruna on February 18, 2000
    • BrO pro le and SCD model comparison
    • OC lO pro le and SCD model comparison
  • Summary of BrO measurements during the eight LPMA/DOAS balloon ights
    • BrO pro le measurements
    • BrO VCD comparisons with satellite and ground-based instruments
• The rst measurement of a BrO pro le in the free troposphere
  • Methodology and Measurements
  • Discussion of the free tropospheric BrO measurements
• Comparison of the inorganic and organic bromine budget for the Arctic lower stratosphere in winter 1998/1999
  • Methodology of the comparison
  • Discussion of the comparison
  • A recent history of total organic and inorganic stratospheric bromine
• Lagrangian case studies for the interpretation of enhanced OC lO measurements at mid and high latitudes
  • The Lagrangian tra jectory box model LABMOS
  • Case study of the in-vortex ight at Kiruna on February 10, 1999
  • Case study of the out-of-vortex ight at León on November 23, 1996
• Conclusions and Outlook

Zielsetzung und Themenschwerpunkte (Objectives and Key Themes)

This dissertation investigates the inorganic bromine budget in the stratosphere, particularly focusing on the role of bromine oxide (BrO) in ozone depletion cycles. The work examines the ndings from eight balloon-borne measurements conducted between 1996 and 2000, utilizing the Differential Optical Absorption Spectroscopy (DOAS) technique to measure BrO and chlorine dioxide (OClO) concentrations.

• Analyzing the stratospheric bromine budget over a four-year period.
• Improving the understanding of the chemistry of stratospheric bromine, especially the formation and destruction of BrO.
• Investigating the role of heterogeneous reactions on stratospheric aerosols and polar stratospheric clouds (PSCs) in bromine activation.
• Exploring the presence of BrO in the free troposphere, analyzing its distribution and potential sources.
• Comparing the inorganic bromine budget determined from BrO measurements with the standard organic bromine method.

Zusammenfassung der Kapitel (Chapter Summaries)

The dissertation is structured as follows:

• Chapter 2 provides a comprehensive overview of the chemistry of the stratosphere, highlighting the importance of halogens, particularly bromine and chlorine, in ozone destruction cycles.
• Chapter 3 delves into the principles and technical aspects of the direct sunlight balloon-borne DOAS measurement technique employed in the study. It describes the instrument used, the retrieval algorithms for SCDs and pro les, and the main sources of error in the measurements.
• Chapter 4 presents the results of the eight LPMA/DOAS balloon ights, detailing the time evolution of SCDs and retrieved pro les for BrO and OC lO. It also examines the agreement between the measurements and model predictions from the 3-D Chemical Transport Model (SLIMCAT).
• Chapter 5 focuses on the rst measurement of a BrO pro le in the free troposphere, showcasing the methodology and the statistical signi cance of the nding. The chapter also explores potential sources of tropospheric BrO and its implications for tropospheric chemistry.
• Chapter 6 compares the inorganic bromine budget determined from BrO measurements and photochemical modeling with the standard organic bromine method. This comparison is based on the data obtained during the Arctic winter 1998/1999, and it provides insights into the potential in ux of inorganic bromine from the troposphere into the stratosphere.
• Chapter 7 explores the observations of enhanced OC lO measurements at mid and high latitudes. The chapter introduces a Lagrangian tra jectory box model (LABMOS), which is used to interpret the measurements and compare them with the SLIMCAT model results. Two case studies - one from the Arctic vortex and the other from mid-latitudes - are analyzed to understand the processes leading to OC lO formation in di erent environments.

Schlüsselwörter (Keywords)

The dissertation delves into the key areas of stratospheric bromine and chlorine chemistry, focusing on the following keywords:

• BrO (Bromine oxide)
• OClO (Chlorine dioxide)
• Ozone depletion
• DOAS (Di erential Optical Absorption Spectroscopy)
• Balloon-borne measurements
• Heterogeneous reactions
• PSCs (Polar Stratospheric Clouds)
• Tropospheric BrO
• Lagrangian model
• SLIMCAT (Single Layer Isentropic Model for Chemistry And Transport)
• LABMOS (LAgrangian Box MOdel for the Stratosphere)