The main objective of this study was to investigate the vertical distribution of aerosols
over Durban in relation to the vertical stability structure and horizontal transport of air
masses. The importance of aerosols in the region is well recognised and recently there
have been many international experiments which have focused on aerosol distribution
over the subcontinent. Durban is situated at the approximate centre of a giant plume that
is known to transport aerosols and trace gases off the east coast of southern Africa and
is therefore strategically located for an investigation of the vertical distribution of
aerosols.
The vertical distribution of aerosols over Durban was measured using a LIDAR (Light
Detection And Ranging) system on selected cloud free days in 1997. Backward
trajectory modelling was used at selected pressure (standard) levels to determine the
origin and transport pathways of aerosols. Six case studies are presented in an attempt to
gain insight into the relationship between the vertical distribution of aerosols and
absolutely stable layers.
The results of the study revealed that the occurrence of absolutely stable layers governs
the vertical distribution of aerosols in the troposphere. An absolutely stable layer at
~5km (~500hPa) appears to be the most effective in capping and trapping aerosols in
the atmosphere. Below 5km, the atmosphere was charcterised by marked stratification
and relatively higher concentration of aerosols. Above 5km, the concentrations were
much lower, but generally increased slightly with height. Low aerosol concentrations
are observed during post-frontal situations and relatively higher concentrations during
anticyclonic conditions.
The background to the problem and the objectives of this investigation are elaborated in
Chapter 1. A description of the data sets and derived meteorological variables, along
with the methodologies applied in this thesis, are given in Chapter 2. A theoretical
review of aerosols, including their sources, effects and distribution over the globe and
southern Africa, is discussed in Chapter 3. Atmospheric circulation and weather patterns
and their relationship to the transport and dispersion of aerosols are described in
Chapter 4. The results of the study and an analysis of the major findings are presented in
Chapter 5. Finally, Chapter 6 summarises the major findings of this dissertation. / Thesis (M.Sc.)-University of Natal, Durban, 2000.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ukzn/oai:http://researchspace.ukzn.ac.za:10413/3979 |
| Date | January 2000 |
| Creators | Rahman, Muhammad Ziaur. |
| Contributors | Diab, Roseanne D. |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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