Evidence of a LNO_X influence on middle/upper troposphere ozone‐mixing ratios at Dakar, Senegal during Northern Hemisphere summer season

Abstract

We present results for the vertical distribution of tropospheric ozone from 40 measurements at Dakar, Senegal (14.59• N, 17.5

The Evolution of the Wave‐One Ozone Maximum During the 2017 LASIC Field Campaign at Ascension Island

“…We show: (1) the WOOM's evolution is driven by episodic biomass burning plumes that are transported from Southern Africa in August and September; (2) polluted air from biomass burning can vary in height with ozone rich layers in the 2–5 km range; (3) easterly winds typically produce higher ozone mixing ratio values at Ascension Island, but we also observed higher ozone mixing ratios with westerly winds and back trajectories suggests a South American origin; (4) there is only limited evidence of the AEJ‐S in its strong phase (SJ) as would be expected based on results from Mari et al. (2008) and Adebiyi and Zuidema (2016); (5) high ozone mixing ratios are frequently observed in the 500–300 hPa layer, suggestive of a LNO X source from Africa which has been observed in similar layers and linked to LNO X near to and north of the Equator (Jenkins et al., 2008, 2012, 2014, 2015) and becomes more prominent during the last week in September and October in the observations; (6) the TEJ with its large anticyclonic circulation at 200 hPa is the dominant mechanism for cross‐equatorial transport of LNO X produced O 3 in the upper troposphere from West Africa to the South Tropical Atlantic Ocean.…”

“…(2006) show that lightning activity over Africa continues to enhance TOC values across the Southern Atlantic Ocean leading to the Tropical Ozone Paradox, where TOC values exceed those in the Northern Tropical Atlantic although biomass burning is active in West Africa. The pattern of elevated O 3 mixing ratios has also been found in Equatorial Africa (Jenkins et al., 2008) and the Northern Tropical Atlantic during the West African wet season where peaks in middle troposphere ozone mixing ratios are found downstream and at continental outflow regions of West Africa at Cape Verde and Dakar Senegal (Barret et al., 2010; Jenkins et al., 2012, 2014). Elevated middle troposphere O 3 mixing ratios at Barbados are observed downstream of tropical disturbances and linked to LNO X lightning (Jenkins et al., 2015).…”

“…(5) high ozone mixing ratios are frequently observed in the 500-300 hPa layer, suggestive of a LNO X source from Africa which has been observed in similar layers and linked to LNO X near to and north of the Equator (Jenkins et al, 2008(Jenkins et al, , 2012(Jenkins et al, , 2014(Jenkins et al, , 2015 and becomes more prominent during the last week in September and October in the observations; (6) the TEJ with its large anticyclonic circulation at 200 hPa is the dominant mechanism for cross-equatorial transport of LNO X produced O 3 in the upper troposphere from West Africa to the South Tropical Atlantic Ocean.…”

“…Lightning produces NO X leading to the production of ozone when sunlight is present. Elevated ozone mixing ratios in the middle and upper troposphere produced from lightning can be horizontally transported over long‐distances while undergoing subsidence over the Atlantic Ocean, leading to a middle‐troposphere peak (Jenkins et al., 2012, 2014; Thompson et al., 2000). During the wet season in the Southern Hemisphere, Thompson et al.…”

Effect of cloud-to-ground lightning and meteorological conditions on surface NOx and O3 in Hong Kong

“…In addition, corona discharge in the vicinity of a lightning flash can also produce ozone directly (Bozem et al, 2014). Increase of O 3 concentration in the middle and upper troposphere associated with lightning and lightning produced NO x had been reported in many studies Zhang et al, 2012;Jenkins et al, 2014). However, influence of lightning and lightning induced NO x on O 3 concentration could be different in the atmospheric surface layer because of relatively more complex meteorological conditions and atmospheric chemical reactions.…”