Surface ozone variability and trends over the South African Highveld from 1990 to 2007. Issue 7 (9th April 2014)

• Record Type: Journal Article
• Authors: Balashov, Nikolay V.; Thompson, Anne M.; Piketh, Stuart J.; Langerman, Kristy E.
• Is Part Of: Journal of geophysical research. Volume 119:Issue 7(2014:Jul.)
• Page Start: 4323
• Page End: 4342
• Publication Date: 2014-04-09
• Subjects: surface ozone trends -- South African Highveld -- ENSO -- El‐Nino -- African air pollution; Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1002/2013JD020555
• Languages: English
• ISSNs: 2169-897X

Abstract

Abstract: Surface ozone is a secondary air pollutant formed from reactions between nitrogen oxides (NO x = NO + NO2 ) and volatile organic compounds in the presence of sunlight. In this work we examine effects of the climate pattern known as the El Niño–Southern Oscillation (ENSO) and NO x variability on surface ozone from 1990 to 2007 over the South African Highveld, a heavily populated region in South Africa with numerous industrial facilities. Over summer and autumn (December–May) on the Highveld, El Niño, as signified by positive sea surface temperature (SST) anomalies over the central Pacific Ocean, is typically associated with drier and warmer than normal conditions favoring ozone formation. Conversely, La Niña, or negative SST anomalies over the central Pacific Ocean, is typically associated with cloudier and above normal rainfall conditions, hindering ozone production. We use a generalized regression model to identify any linear dependence that the Highveld ozone, measured at five air quality monitoring stations, may have on ENSO and NO x . Our results indicate that four out of the five stations exhibit a statistically significant sensitivity to ENSO at some point over the December–May period where El Niño amplifies ozone formation and La Niña reduces ozone formation. Three out of the five stations reveal statistically significant sensitivity to NO x variability, primarily in winter and spring. Accounting for ENSO and NO x effects throughout the study period of 18 years, two stations exhibit statistically significant negative ozone trends in spring, one station displays a statistically significant positive trend in August, and two stations show no statistically significant change in surface ozone. Key Points: Surface ozone variability at Highveld is examined during 1990–2007 ENSO and NOx affects surface ozone over the South African Highveld Surface ozone on the Highveld has not increased over 1990–2007