Role of synoptic weather systems in surface ozone concentration in Durban region.
Langa, Mduduzi Amos.
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Measurements of surface ozone in Durban have been undertaken since September 1994 until August 1995 using a Dasibi ozone monitor model 1108. There is a seasonal variation in surface ozone with a small amplitude of 6.5 ppb. The mean maximum of 12.5 ppb is experienced in August and the minimum in December (6 ppb). The late winter peak and the sharp rise from June to July is possibly related to the greater accumulation of ozone at the surface due to the poor dispersion, higher frequency of inversions and lower mixing depth. The study also focuses on the relationship between synoptic weather systems and daily ozone concentrations in an attempt to establish if any relationship exists. The analysis suggests that there is an increase in ozone concentration during the pre-frontal and established high pressure systems and a reduction in ozone under postfrontal conditions. The mean diurnal variation in surface ozone depicts a maximum between solar noon and 14:00, which is typical of an urban-industrial environment, in which ozone precursor gases have built up during the morning. However, a secondary peak in the early morning during winter and autumn was more difficult to explain and is thought to be due to the transport of ozone from the interior in the mountain-plain wind systems. Comparison of ozone values at Durban with results available from the other locations in South Africa such as Cape Point and the Eastern Transvaal Highveld has been undertaken. Ozone values at Durban are lower than Cape Point, which is a representative of a background monitoring station. It ls hypothesised that those low ozone concentrations may be due to high NOx which in turn depletes ozone.