A semi-Lagrangian view of ozone production tendency in North American outflow in the summers of 2009 and 2010

Abstract

was observed in both events, but due to differing transport mechanisms, ozone production tendency differed between the two. A layer of net ozone production was found at 2 km a.s.l. over the Azores in the first event plume, apparently driven by PAN decomposition during subsidence of air mass in the Azores-Bermuda High. In the second event, net ozone loss occurred during transport in the lower free troposphere, yet observed

Ten-year chemical signatures associated with long-range transport observed in the free troposphere over the central North Atlantic

“…As shown in Table 2, the mean O 3 mixing ratios in the NA-anthro sub-categories were all significantly different from each other, possibly suggesting O 3 levels were sensitive to transport heights and distances. The mean O 3 level of NA-anthro-low was lower than NA-anthro-lifted, which is a result of more efficient O 3 removal in low altitude transport and potential O 3 production by PAN decomposition in the subsidence stage of the lifted transport (Hudman et al, 2004;Zhang et al, 2014). The lower O 3 of NA-anthro-aged was generally due to the longer transport time and lack of O 3 precursor sources over the North Atlantic.…”

“…For the same reasons, NO y for NA-anthro-lifted was much higher than that for NA-anthro-low due to accumulation of PAN and less efficient loss of NO y at higher altitude. This transformation of NO y has been studied in detail for two transport events to PMO by Zhang et al (2014). NO y of NA-anthro-low was lower than the other transport patterns, reflecting efficient removal of NO y in the moist marine boundary layer air.…”

“…For the comparisons of d [O 3 ]/d[CO] at a given location, such as PMO, the differences in CO loss for pollution impacted transport should not be significant. Zhang et al (2014) estimated 10% and 12% CO loss due to photochemistry for two transport events of polluted plume having significant different OH concentrations and transport pathways. Thus, differences in observed d [O 3 ]/d [CO] at PMO should mainly reflect varying emission strength and ozone chemistry for the pollution impacted transport.…”

“…Honrath et al (2004) found a higher summertime d [O 3 ]/d[CO] (~1.0) in the free troposphere over the central North Atlantic and suggested potential O 3 production during transport from North America. A previous study (Zhang et al, 2014) investigated the evolution of d [O 3 ]/d [CO] during selected transport events of pollution plumes from North America to PMO in a semi-Lagrangian view, using data from PMO and a chemical transport model. It was found that photochemical CO loss can also contribute to increases in d [O 3 ]/d [CO] in long-range transport, so the higher d [O 3 ]/d [CO] at PMO compared to places closer to emission sources (i.e., over the U.S.) were due to not only photochemical ozone production but also CO loss.…”

Fire Influences on Atmospheric Composition, Air Quality and Climate

“…They found dO 3 /dCO to range from −0.1 to 0.9, due to factors such as fire emissions, efficiency of combustion, chemical and photochemical reactions, aerosol effects on chemistry and radiation, and local and downwind meteorological patterns. However, other recent studies suggest that positive dO 3 /dCO is not always an indicator of an ozone-producing region [33,34], especially in cases where there is substantial CO loss in a plume due to intense production of OH from ozone. Parrington et al [35,36] discussed in detail ozone production in fire plumes in North America and the northern Atlantic.…”