Abstract
Near-surface ozone is enhanced under particular chemical reactions and physical processes. This study showed the seasonal variation of near-surface ozone in Nicosia, Cyprus and focused in summers when the highest ozone levels were noted using a seven year hourly dataset from 2007 to 2014. The originality of this study is that it examines how ozone levels changed under heatwave conditions (defined as 4 consecutive days with daily maximum temperature over 39 °C) with emphasis on specific air quality and meteorological parameters with respect to non-heatwave summer conditions. The influencing parameters had a medium-strong positive correlation of ozone with temperature, UVA and UVB at daytime which increased by about 35% under heatwave conditions. The analysis of the wind pattern showed a small decrease of wind speed during heatwaves leading to stagnant weather conditions, but also revealed a steady diurnal cycle of wind speed reaching a peak at noon, when the highest ozone levels were noted. The negative correlation of NOx budget with ozone was further increased under heatwave conditions leading to steeper lows of ozone in the morning. In summary, this research encourages further analysis into the persistent weather conditions prevalent during HWs stimulating ozone formation for higher temperatures.
Highlights
Air pollution has gained a growing interest the past decades due to its negative effects on human health; cardiovascular and respiratory related diseases[1,2,3,4,5,6]
The results from the present analysis could improve our understanding of near-surface ozone with regards to chemical precursors, catalytic factors and physical processes; vertical and horizontal advection
In the previous section the chemical reactions (CHEM), VADV and horizontal advection (HADV) factors were analysed under HW and NHW conditions; indicating that all the observed parameters had an effect, evident by the noteworthy correlation, on ozone measurements with increased effect under HW conditions when the synoptic situation favoured stagnant atmospheric conditions
Summary
Air pollution has gained a growing interest the past decades due to its negative effects on human health; cardiovascular and respiratory related diseases[1,2,3,4,5,6]. Ozone does depend on the quantities of the precursors, and on the ability of the atmosphere to form or deplete ozone and under favourable meteorological conditions such as high temperature, intense solar radiations, long sunshine hours and low wind speed/direction, all characteristics of heatwaves. The increase of frequency of heatwaves during the past decades urges the need for identification of the influencing meteorological and anthropogenic factors in ozone spikes in each region. This is becoming more important to regions like the eastern Mediterranean and Middle East where www.nature.com/scientificreports/. Ooka et al.[12] argued that higher temperatures and calm weather conditions (low wind speed) promoted ozone formation and limited ozone dispersion in urban areas whereas in rural areas the downward vertical advection enhanced ozone levels[12]
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