Regional and hemispheric impacts of anthropogenic and biomass burning emissions on summertime CO and O₃ in the North Atlantic lower free troposphere

Abstract

[1] We report summertime measurements of CO and O 3 obtained during 2001-2003 at the PICO-NARE mountaintop station in the Azores. Frequent events of elevated CO mixing ratios were observed. On the basis of backward trajectories arriving in the free troposphere and global simulations of biomass burning plumes, we attribute nearly all these events to North American pollution outflow and long-range transport of biomass burning emissions. There was a high degree of interannual variability in CO levels: median [CO] ranged from 65 ppbv in 2001 to 104 ppbv in 2003. The highest concentrations were associated with transport of Siberian fire emissions during summer 2003, when Siberian fire activity was unusually high. Ozone mixing ratios also increased (by up to $30 ppbv) during the fire events. These findings demonstrate the significant hemispheric scale impact that biomass burning events have on background CO and O 3 levels. O 3 enhancements of similar magnitude were also observed in North American pollution outflow. O 3 and CO were correlated during North American outflow events, with a slope averaging 1., ppbv/ppbv) when no fire impact was present. This slope is more than 80% larger than early 1990s observations made in the eastern United States and nearshore outflow region, even after accounting for declining U.S. CO emissions and for CO loss during transport to the Azores, and is not consistent with simple dilution of U.S. outflow with marine background air. We conclude that a significantly larger amount of O 3 production occurred in the air sampled during this study, and we suggest several potential reasons for this, each of which could imply potentially significant shortcomings in current estimates of the hemispheric impact of North American emissions on tropospheric ozone and should be evaluated in future studies.

Interannual variability of ozone and carbon monoxide at the Whistler high elevation site: 2002–2006

“…Boreal fires, in addition to their significance in controlling the CO budget, are substantial sources of NOx and NMHCs (Wotawa et al, 2001) and thus additional precursors for ozone formation. These emissions have been shown to have an effect on regional ozone concentrations Val Martin et al, 2006;Honrath et al, 2004;DeBell et al, 2004;Bertschi and Jaffe, 2005). Pfister et al (2006) …”

“…The basis for the CO and O 3 comparison is the assumption that CO mixing ratios are directly related to CO and O 3 precursor emissions such as nonmethane hydrocarbons and nitrogen oxides, and that changes in CO are indicative of changes in O 3 precursor species and thus would exhibit a relationship with net ozone production (Parrish et al, 1993(Parrish et al, , 1998Honrath et al, 2004). Annual and interannual variability in CO is strongly dependent on both fossil fuel emissions and biomass burning Wotawa et al, 2001;Yurganov et al, 2005).…”

“…To understand the factors affecting O 3 budgets, comparisons of O 3 with CO have been made in North American outflow and also at sites on the west coast of the US (Parrish et al, 1998;Honrath et al, 2004;Val Martin et al, 2006). The basis for the CO and O 3 comparison is the assumption that CO mixing ratios are directly related to CO and O 3 precursor emissions such as nonmethane hydrocarbons and nitrogen oxides, and that changes in CO are indicative of changes in O 3 precursor species and thus would exhibit a relationship with net ozone production (Parrish et al, 1993(Parrish et al, , 1998Honrath et al, 2004).…”

Ozone-CO Correlations in Siberian Wildfire Plumes Observed at Rishiri Island

“…This feature is in great contrast to the O3 enhancement in the industrially-polluted air masses observed at Rishiri Island, which typically shows positive and tight O3 CO correlations. Honrath et al 2004;Bertschi and Jaffe 2005).…”

Perturbations of the optical properties of mineral dust particles by mixing with black carbon: a numerical simulation study

“…In Fig. 1, we show a composite of SEM (scanning electron microscope) images from aerosol samples collected: (a) in an urban location 10 km north of downtown Mexico City (MILAGRO, March 2006); (b) 40 km downwind of the Sacramento urban area in the forested Sierra Nevada foothills, California, USA ; (c) in a rural site in Detling, UK (ClearfLo, January-February, 2012); and (d) at Pico Mountain Observatory, Azores Islands (Portugal) in the North Atlantic Ocean (Honrath et al, 2004;Dzepina et al, 2015). The morphological characteristics of the BC and mineral dust particles are summarized in Table 3.…”