Transport and Distribution of the Short-Lived Halocarbons in the Tropical Tropopause Layer in the Pacific Ocean: the Role of Convection
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Authors
FILUS, MICHAL TADEUSZ
Advisors
HARRIS, NEIL
Date
2017-11-01Awarding Institution
University of Cambridge
Author Affiliation
Chemistry
Qualification
Doctor of Philosophy (PhD)
Language
English
Type
Thesis
Metadata
Show full item recordCitation
FILUS, M. T. (2017). Transport and Distribution of the Short-Lived Halocarbons in the Tropical Tropopause Layer in the Pacific Ocean: the Role of Convection (Doctoral thesis). https://doi.org/10.17863/CAM.17070
Abstract
This PhD thesis investigates the transport and distribution of short-lived halogenated organic
substances in the tropical tropopause layer (TTL) in the Pacific Ocean. Short-lived
halocarbons are one of the major groups of the ozone depleting substances as they provide a
source for the active halogens which decrease ozone in the atmosphere. The TTL serves as
the primary gateway of tropospheric air to enter the stratosphere. The air which enters the
stratosphere is distributed all over the globe. Thus, the research on which tropospheric air
masses go into the TTL, its structure and composition and the transport within is crucial.
This thesis uses the UK Meteorological Office Lagrangian particle dispersion model
NAME to (i) support the flight planning activities and achieve the multi aircraft
coordination in CAST, CONTRAST, ATTREX 2014 campaigns, and (ii) quantify the
amount and distribution of short-lived halocarbons in the TTL, and explain differences in
these vertical distributions and transport characteristics. The halocarbons of interest are
methyl iodide (CH3I), bromoform (CHBr3) and dibromomethane (CH2Br2).
A new NAME procedure was developed and operated successfully to provide routine
simulations and near real-time products suitable for guiding the CAST, CONTRAST and
ATTREX aircraft in order to achieve their mission scientific objectives, and to make
coordinated measurements.
NAME was used post-campaign to analyse distribution of short-lived halocarbons in the
TTL, identify their source regions and transport timescales. A new approach is proposed to
investigate the TTL composition in terms of the boundary layer air influence, and
subsequently quantify CH3I, CHBr3 and CH2Br2 by estimating their boundary layer and
background contribution. The sums of these modelled estimates are in good agreement with
the ATTREX 2014 and 2013 CH3I, CHBr3 and CH2Br2 observations. The quantification of
the contribution of short-lived bromocarbons to the active bromine in the TTL was
achieved, and the results lie within the range of the recent literature studies.
The final focus of this thesis is on how well NAME represents the particle displacement via
convection. Convection is the major transport pathway for the short-lived halocarbons to
reach the TTL. The role of convection in transporting CH3I, CHBr3 and CH2Br2 to the TTL
is assessed using the new convection scheme in NAME. A validation of the performance of
this scheme is provided, showing that it yields improved and more realistic representation
of the particle displacement via convection.
Keywords
short-lived halocarbons transport, tropical tropopause layer chemical structure, atmospheric transport modelling
Sponsorship
Natural Environment Research Council
Identifiers
This record's DOI: https://doi.org/10.17863/CAM.17070
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