Browsing by Author "Ramsay, Lisa Frost."
Now showing 1 - 5 of 5
- Results Per Page
- Sort Options
Item Analysis of surface ozone measurements at Cape Point, SANAE and City of Cape Town.(2013) Mkololo, Thumeka.; Ramsay, Lisa Frost.This study presents an investigation of surface ozone (O₃) at SANAE (2002 to 2009), Cape Point (1997 to 2009), Molteno (1997 to 2007) and Goodwood (2000 to 2006). The Cape Point data was statistically separated to background and non-background (anthropogenic) contributions. The main aim of the study was to investigate diurnal cycles, seasonal cycles, the weekend effect, and any long term trends in surface O₃, as well as assess meteorological controls on surface O₃ at these stations. The observed O₃ concentrations were higher during the day than at night at all stations, with urban stations (Molteno and Goodwood) showing more pronounced peak-to-peak variations relative to the marine stations (SANAE and Cape Point). The ‘weekend effect’ was evident at Molteno and Goodwood with higher O₃ and lower NOₓ concentrations on 'weekends relative to weekdays. The weekend effect on O₃ was more pronounced in winter at Goodwood and Molteno. Maximum monthly average concentrations were observed in spring at Goodwood and Molteno, with minimum in winter. The SANAE and Cape Point background O₃ maxima were observed in winter (June to August) with minima in summer (January to February). The Cape Point non-background O₃ maximum was observed in September with a minimum in summer (January). The seasonal cycles at marine sites appear to be driven by O₃ photolysis. Wind speeds played a critical role in O₃ concentrations, particularly in the continental environment. At Goodwood, high NOₓ levels are associated with low wind speeds. At SANAE, no significant O₃ differences were observed between low wind speeds and high wind speeds while at Cape Point, differences were more evident during the winter months. A decreasing O₃ trend in monthly averages was observed from 1997 to 2006 at Molteno while Goodwood demonstrated an increase of O₃ monthly averages with decreasing NOₓ monthly averages from 2000 to 2006.Item An assessment of the NAME III model capability in reproducing seasonal variation of SO₂ and O₃ pollutant concentrations : a focus on the Mpumalanga Highveld area.(2015) Sibiya, Bhekizizwe Alphios.; Thambiran, Tirusha.; Ramsay, Lisa Frost.The South African Weather Service Air Quality Modelling programme initiative has a long term goal to develop a system capable of generating atmospheric air quality forecasts for a range of primary and secondary pollutants in order to advise and warn the public on possible high levels pollutant concentration in the air and also provide support in relevant policy development. In this study a pilot NAME III air quality modelling system was developed and tested for its performance in simulation of sulphur dioxide (SO₂) and ozone (O₃) concentrations over the Mpumalanga Highveld. The agreement of model predictions generated in this study with observations was evaluated using the statistical analysis of the monthly averages of SO₂ and O₃ concentrations based on the Bias, NMB, RMSE, NRMSE statistical measures. In addition, the seasonal distribution and variation of the modelled SO₂ and O₃ concentrations over the South African domain were assessed. The results demonstrate that the modelling system under-predicts SO₂ and O₃ concentrations. However, in most cases the modelled concentrations are in the same order of magnitudes with the measured data except for two incidences of very low modelled SO₂ in Middelburg during April and May months, which may be attributed to the poor initialisation of the model. For each season, the model was initialised for the first five days to allow for the pre calculation of the initial pollutant concentrations. This was not possible for the autumn season as no Numerical Weather Prediction (NWP) data were available for initialisation during this period. In general the overall results indicate that the NAME III modelling system is a promising and cost-effective tool for providing real time air quality forecasts, in particular, the ground level O₃ concentration in South Africa. The NAME III modelling system therefore has the potential to be used operationally as a national air quality forecasting system and, as a tool to conduct air quality modelling studies. Specifically the modelling system could assist in the amendment and development of relevant air quality policies that have a direct impact on the environment, health and other related sectors. However, it is suggested that while more evaluation exercises must be undertaken, advancements in term of a comprehensive emissions inventory and improved representation of meteorological information are needed.Item Evaluating the contribution of ship exhaust gas emissions to air pollution and the urban carbon footprint: a case study of Durban Port.(2014) Manqele, Nkosinathi Michael.; Ramsay, Lisa Frost.The Durban Port in South Africa is the busiest port in Africa and has the second largest container terminal in the southern hemisphere. Approximately 60% of the country’s exports and imports pass through this port. It is one of the few ports in the world that is in close proximity to the central business district (CBD). This proximity has a positive spin-off in terms of tourism, recreation and accessibility to transport and other business activities. However, it also has a negative impact to the city’s population due to air pollution resulting from the port activities, particularly from the marine mobile sources. Like many other ports globally, Durban Port suffers from the lack of proper quantification of emissions resulting from ships in the port. The aim of this study was therefore to calculate the pollution from ships in Durban Port between the 1st of April 2012 and the 31st of March 2013 (one year). The activity-based method was utilized to estimate ships emissions of sulphur dioxide (SO2), oxides of nitrogen (NOX), particulate matter (PM10), hydrocarbons (HC) and carbon dioxide (CO2). This method uses emission factors for specific engines, the types of activities (also known as modes of operation) in the port, the time spent on each activity and the load factors per activity. The types of activities considered were manoeuvring, hoteling and loading/unloading. The types of vessels studied were ocean going vessels (OGVs) and harbour crafts. The results indicate that OGVs (particularly container ships) emit higher levels of pollutants than the harbour crafts in Durban Port. This is explained by the higher number of OGVs relative to harbour crafts, and the higher emissions per OGV per operational hour relative to those of harbour crafts. Auxiliary engines accounted for a higher proportion of emissions of NOX and HC when compared to propulsion engines and boilers, while the boilers emitted higher levels of SOX, PM10 and CO2. This is because both the auxiliary engines and the boilers remain operational in all three activities studied. The emissions inventory for Durban Port was compared with other ports globally including JN Port in India, the Port of Los Angeles in the United States and the Port of Copenhagen in Denmark. Cambridge Environmental Research Consultants’ (CERC) Atmospheric Dispersion Modelling System (ADMS) was used to model ambient concentrations of NOX, SO2, and PM10 from ships in port. The results were compared with and found to be below the South African National Ambient Air Quality Standards (NAAQS) published in line with Section 9 of the National Environmental Management: Air Quality Act 39 of 2004. However, the results indicate that emissions from ships are significant and should not be ignored in cumulative air quality assessments and the calculation of the urban carbon footprint.Item Southern African palaeoclimates and variability : the story from stalagmites, pollen and coral.(2005) Ramsay, Lisa Frost.; Ellery, William Nolan.Compared to extensive study in the northern hemisphere, very little is known of southern African palaeoclimates. This study aimed to extend understanding of the nature of and controls on southern African palaeoclimates of the last 40 000 years. Through a study of the approximately 20 000 year long Makapansgat and Wonderkrater palaeoclimatic records, and an extensive literature review of southern African palaeoclimatic studies, a number of common rainfall and temperature fluctuations were detected across the summer rainfall region. Based on these trends, general models of rainfall and temperature changes over time were developed for the region. The analysis of a coral core, derived from a Porites lutea head from Sodwana Bay, covering the last 116 years, indicated higher frequency climatic fluctuations over the last century. Climatic variability on the long- and short-term could then be related to known atmospheric processes through application of the Tyson (1986) model for southern Africa atmospheric circulation. North-south shifts in mean circulation dominate climatic variability in the region but there are also regular disturbances to this mean, such as in the form of the EI Nino - Southern Oscillation. The fluctuations seen in present and palaeoclimatic records are the result of a complex interaction between internal and external mechanisms of climate change. Wavelet analyses of recorded and proxy climatic datasets highlighted the cycles which dominate southern African climatic variability on timescales from years to millennia. The causes of these cycles were then assessed in the context of established solar, atmospheric and oceanic models. Wavelet analyses also provided an indication of frequency changes over time and were therefore useful for detecting climate change. An analysis of proxy and recorded climatic datasets for southern African rainfall over the last 100 years indicated a frequency modulation of the 18 year rainfall cycle, which was first described by Tyson (1971). This variation may be related to anthropogenic climate change. It became apparent from this study that there is a need for increased scientific interest in the palaeoclimatic trends of the region. The number of continuous, high-resolution datasets needs to be increased to allow for comparison and confirmation of various trends with records from sites across the globe. An understanding of the nature of regional and global teleconnections is essential before reliable climate change models can be established. There is also a need for further understanding of short-term southern African climate variability on inter-annual timescales.It is only once we have an understanding of the natural climatic variability of the region ,and its inherent cyclicity,that we can begin to distinguish the impact of anthropogenic activities on climate.Item Synoptic influences on air pollution events in the Durban South Basin, 2006 to 2010.(2013) Tularam, Hasheel.; Ramsay, Lisa Frost.This study aimed to assess the relationships (if any) between air pollutant measurements in the Durban South Basin (DSB) and (i) local meteorology, (ii) community reports of pollution incidents in Durban, and (iii) air quality and meteorology in Cape Town on the days preceding the Durban South Basin events. With the use of daily synoptic charts and various meteorological variables at an hourly resolution, it was established that air pollution events were better associated with local meteorological events than a community complaint database. Visual analyses of graphed meteorological conditions during the course of air pollution events revealed three clear meteorological scenarios associated with these: 1. A pre-frontal scenario; 2. A scenario showing inversion conditions but no approaching front, and generally low wind speeds; and 3. A post-frontal scenario, likely to be associated with stack downwash under higher wind speeds with the passing of a front. ANOVA revealed significant differences between peak PM10 and average PM10 across scenarios, with Scenario 3 showing highest average and peak PM10. At the Wentworth monitoring station, 24.4% of pollution incidents fell under Scenario 1, 64.2% under Scenario 2, and 5.7% under Scenario 3 between 2006 and 2010. A further 5,7% of the air pollution incidents did not fall under these three scenarios. The latter were not associated with fronts, and did not show inversion conditions, and are likely to be associated with intermittent industrial pollution events. Further statistical analysis assessed the relationships (if any) between various meteorological variables, traffic levels and air pollution concentrations at the Wentworth station between 2006 and 2010. Findings show that delta temperature (change in temperature with height) is the strongest explanatory variable with respect to PM10, wind speed the second strongest, and traffic levels the third strongest. On average, PM10 concentrations increased with increasing delta temperature, decreasing wind speed, and increasing traffic levels. The pressure minimum at Durban associated with an approaching front showed a negative relationship with PM10 during pre-frontal events, but this variable was not significant at the 95% confidence level. This tentatively suggests that even when controlling for frontal influences on delta temperature, lower pressure minima (i.e. stronger frontal systems) are associated with higher pollution levels. Pollution maxima at various Cape Town stations and pressure minima in Cape Town prior to the incident in the DSB showed no relationships with incident PM10 levels at Wentworth. As such, pollution concentrations and meteorology in Cape Town as a front approaches do not appear to be effective predictors of pollution conditions in the DSB when the front approaches there.