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

Table of Contents

1 Introduction

2 Halogen species and their importance in atmospheric chemistry

2.1 Stratospheric Ozone

2.2 Tropospheric Ozone

2.3 Stratospheric gas phase chemistry related to ozone

2.3.1 Chapman Chemistry

2.3.2 Catalytic Cycles

2.3.3 Nitrogen chemistry in the stratosphere

2.3.4 Halogen chemistry in the stratosphere

2.4 Heterogeneous chemistry on PSCs leading to the Ozone Hole

2.4.1 Heterogeneous chemistry on sulphate aerosols

2.5 Fundamental Stratospheric Dynamics

2.6 The atmospheric halogen budget

3 Measurement Technique : Direct Sunlight Balloon Borne DOAS (Differential Optical Absorption Spectroscopy)

3.1 Solar Radiation and the Solar Spectrum

3.1.1 Interaction of light with matter

3.1.2 Lambert-Beer's Law - Optical Absorption Spectroscopy

3.2 Differential Optical Absorption Spectroscopy (DOAS)

3.3 The DOAS double spectrograph for balloon-borne measurements

3.3.1 Noise sources of the measurements

3.4 The LPMA/DOAS balloon payload

3.4.1 The behaviour of the DOAS spectrograph during the balloon flights and its impact on the BrO evaluation

3.4.2 The BrO DOAS evaluation

3.4.3 The OClO DOAS evaluation

3.5 Determination of the SCD offset in the Fraunhofer reference - Langley Plot

3.6 Summary of the error sources of the bromine oxide SCD measurements

3.7 Profile Retrieval

3.7.1 Raytracing

3.7.2 AMF matrix inversion

3.7.3 Errors of the inversion technique

3.7.4 Differential Onion Peeling technique

3.8 Modelling of SCDs

4 Results and Discussion of the LPMA/DOAS balloon flights

4.1 The sunset flight at León on November 23, 1996

4.1.1 BrO profile and SCD model comparison

4.1.2 OClO profile and SCD model comparison

4.2 The sunset flight at Kiruna on February 14, 1997

4.2.1 BrO profile and SCD model comparison

4.2.2 OClO profile model comparison

4.2.3 O3 profile model comparison

4.2.4 NO2 profile model comparison

4.2.5 Summary of the model comparison

4.3 The sunrise flight at Gap on June 20, 1997

4.3.1 BrO profile and SCD model comparison

4.4 The sunset flight at León on March 19, 1998

4.4.1 BrO profile and VCD comparison with GOME

4.5 The sunset and sunrise flight at Kiruna on August 19/20, 1998

4.5.1 BrO profile and SCD model comparison for the sunset

4.5.2 BrO SCD model comparison for the sunrise

4.6 The sunset flight at Kiruna on February 10, 1999

4.6.1 BrO profile and SCD model comparison

4.6.2 OClO profile and SCD model comparison

4.7 The sunrise flight at Gap on June 25, 1999

4.8 The sunset flight at Kiruna on February 18, 2000

4.8.1 BrO profile and SCD model comparison

4.8.2 OClO profile and SCD model comparison

4.9 Summary of BrO measurements during the eight LPMA/DOAS balloon flights

4.9.1 BrO profile measurements

4.9.2 BrO VCD comparisons with satellite and ground-based instruments

5 The first measurement of a BrO profile in the free troposphere

5.1 Methodology and Measurements

5.2 Discussion of the free tropospheric BrO measurements

6 Comparison of the inorganic and organic bromine budget for the Arctic lower stratosphere in winter 1998/1999

6.1 Methodology of the comparison

6.2 Discussion of the comparison

6.3 A recent history of total organic and inorganic stratospheric bromine

7 Lagrangian case studies for the interpretation of enhanced OClO measurements at mid and high latitudes

7.1 The Lagrangian trajectory box model LABMOS

7.2 Case study of the in-vortex flight at Kiruna on February 10, 1999

7.3 Case study of the out-of-vortex flight at León on November 23, 1996

8 Conclusions and Outlook

Research Objectives and Key Topics

This doctoral thesis investigates the stratospheric inorganic bromine budget between 1996 and 2000 using balloon-borne Differential Optical Absorption Spectroscopy (DOAS) measurements. The primary objective is to advance the understanding of stratospheric bromine chemistry, quantify the total inorganic bromine content, and compare these observational findings with 3-D Chemical Transport Models (CTM) and Lagrangian trajectory simulations to resolve discrepancies in bromine and chlorine partitioning.

• Measurement of BrO vertical profiles using balloon-borne DOAS in various geophysical conditions.
• Determination of the total stratospheric inorganic bromine budget and its comparison with organic bromine precursors.
• Detection and analysis of OClO as an indicator of chlorine activation in the Arctic and at mid-latitudes.
• Development and implementation of an improved DOAS evaluation algorithm and a Lagrangian trajectory box model (LABMOS).
• Investigation of free tropospheric BrO to close the gap between integrated balloon profiles and total atmospheric column measurements.

Excerpt from the Book

Summary of Chapters

1 Introduction: Provides a comprehensive overview of the chemical composition and dynamics of the atmosphere, highlighting the ozone depletion problem and the motivation for investigating the bromine budget.

2 Halogen species and their importance in atmospheric chemistry: Describes the fundamental stratospheric chemistry, catalytic cycles, and the specific role of bromine, chlorine, and nitrogen species in ozone depletion.

3 Measurement Technique : Direct Sunlight Balloon Borne DOAS (Differential Optical Absorption Spectroscopy): Details the DOAS measurement technique, the balloon-borne instrumentation, data retrieval algorithms, and error sources.

4 Results and Discussion of the LPMA/DOAS balloon flights: Presents and discusses the data obtained from eight successful balloon flights, including detailed comparisons with model results.

5 The first measurement of a BrO profile in the free troposphere: Documents the pioneering measurement of free tropospheric BrO, providing evidence for its presence based on inter-comparison of balloon and satellite data.

6 Comparison of the inorganic and organic bromine budget for the Arctic lower stratosphere in winter 1998/1999: Analyzes the bromine budget by comparing inorganic bromine inferred from balloon measurements with organic precursor measurements.

7 Lagrangian case studies for the interpretation of enhanced OClO measurements at mid and high latitudes: Utilizes the LABMOS model to study OClO enhancements and validate the interpretation of chlorine activation.

8 Conclusions and Outlook: Summarizes the major scientific findings and suggests future directions for atmospheric research and instrument validation.

Keywords

Stratosphere, Ozone depletion, Bromine budget, BrO, OClO, DOAS, Balloon-borne measurements, Atmospheric chemistry, Lagrangian modelling, PSCs, Tropospheric bromine, Stratospheric dynamics, Photolysis, Chemical Transport Models, Trace gas detection

Frequently Asked Questions

What is the primary scientific focus of this dissertation?

The thesis investigates the stratospheric inorganic bromine budget from 1996 to 2000 using balloon-borne DOAS measurements to understand its role in catalytic ozone depletion.

Which chemical species are central to this research?

The main species studied are Bromine monoxide (BrO), Chlorine dioxide (OClO), Nitrogen dioxide (NO2), Ozone (O3), and various organic bromine and chlorine source gases.

What is the core research objective of the study?

The primary goal is to accurately quantify the stratospheric inorganic bromine content and resolve the differences between observational data and current photochemical models.

Which methodology is employed to retrieve concentration data?

The work utilizes Differential Optical Absorption Spectroscopy (DOAS) from balloon platforms, applying raytracing and matrix inversion techniques to retrieve vertical profiles from slant column density (SCD) measurements.

What topics are covered in the main body of the work?

The main body covers the atmospheric halogen budget, measurement techniques, detailed analysis of eight balloon flights, comparisons with CTM models (like SLIMCAT), and Lagrangian case studies to interpret OClO measurements.

How can this research be characterized by its keywords?

It is best characterized by keywords such as stratosphere, bromine budget, BrO, OClO, DOAS, balloon-borne measurements, and atmospheric chemical modelling.

Why is the measurement of tropospheric BrO significant?

It provides crucial evidence to explain discrepancies between integrated stratospheric balloon profiles and total atmospheric column measurements obtained by satellites.

What do the Lagrangian case studies reveal about OClO?

The case studies demonstrate that observed OClO enhancements, often interpreted as chlorine activation, require detailed Lagrangian modelling of airmass history to be reconciled with standard photochemical theory.