Intercontinental trans-boundary contributions to ozone-induced crop yield losses in the Northern Hemisphere

Abstract

Abstract. Using a global atmospheric chemistry model, we have quantified for the first time, intercontinental transboundary contributions to crop ozone exposure and subsequent yield reductions in the Northern Hemisphere. We apply four metrics (AOT40, M7, M12, W126) to assess the impacts of 100 % reductions in anthropogenic NO x emissions from North (N) America, South East (SE) Asia and Europe on global and regional exposure of 6 major agricultural crop types to surface ozone, and resultant crop production losses during the year 2000 growing season. Using these metrics, model calculations show that for wheat, rice, cotton and potato, 100 % reductions in SE Asian anthropogenic NO x emissions tend to produce the greatest global reduction in crop production losses (42.3-95.2 %), and a 100 % reduction to N American anthropogenic NO x emissions results in the greatest global impact on crop production losses for maize and soybean (59.2-85.9 %). A 100 % reduction in N American anthropogenic NO x emissions produces the largest transboundary impact, resulting in European production loss reductions of between 14.2 % and 63.2 %. European NO x emissions tend to produce a smaller transboundary impact, due to inefficiency of transport from the European domain. The threshold nature of the AOT40 ozoneexposure metric results in strong dependence of non-local emissions impacts on the local ozone concentration distribution. Our calculations of absolute crop production change under emission reduction scenarios differ between the metrics used, however we find the relative importance of each region's transboundary impact remains robust between metrics. Our results demonstrate that local air quality and emission control strategies have the potential to partly alleviate ozone-induced crop yield loss in continents downstream, in addition to effectively mitigating local ozone-induced production losses.

Tropospheric Ozone Assessment Report: Present-day tropospheric ozone distribution and trends relevant to vegetation

“…At the coarsest resolution, the distribution of areas identified in TOAR-Vegetation as having vegetation at low or high risk of damage from ozone largely matches that predicted by global modelling of M12, AOT40 or W126 (Avnery et al, 2011;Chuwah et al, 2015;Fuhrer et al, 2016;Hollaway et al, 2012;Van Dingenen et al, 2009;). However, the high values for ozone metrics in TOAR-Vegetation at SEA sites tend to be underestimated in modelling studies.…”

“…Here, the TOAR dataset indicates that values are frequently in the range 9000-15000 ppb h, and occasionally > 15000 ppb h. Whereas there are differences in the spatial patterns of measured and modelled values, modelled AOT40 values were in a similar range in southern France and Italy to the TOAR observations in two studies (10000-15000 ppb h, Avnery et al, 2011, and7000-15000 ppb h, Chuwah et al, 2015). In another global study, however, little spatial variation in AOT40 was predicted over Europe, with crop AOT40 values approximately in the range 2000-4500 ppb h (Hollaway et al, 2012). At the regional scale, predictions using the EMEP MSC-W model (Simpson et al, 2012) for 3 m height (more closely aligned with the data in the TOAR database than canopy height ozone usually used by EMEP when using the CLRTAP recommendations for AOT40) provide better spatial agreement with the TOAR dataset for EUR (Simpson et al, 2007).…”

“…However, the high values for ozone metrics in TOAR-Vegetation at SEA sites tend to be underestimated in modelling studies. It is more difficult though to align measurements included in TOARVegetation with modelled data due to uncertainties introduced by comparing site-specific data with grid square values presented at resolutions of 2.8° × 2.8° (Avnery et al, 2011;Hollaway et al, 2012) or 3° × 2° (Chuwah et al, 2015). Differences in the years used also confound detailed comparisons as the global modelling studies tend to have used earlier years such as 2000 (Avnery et al, 2011;Fuhrer et al, 2016;Hollaway et al, 2012) or 2005(Chuwah et al, 2015 whilst TOAR-Vegetation provides 5-year means for the period 2010-2014.…”

“…Firstly, M12 has been used in global and regional model-based assessments of crop losses (e.g. Avnery et al, 2011;Hollaway et al, 2012;Van Dingenen et al, 2009). EC (2008).…”

Interferences in photolytic NO<sub>2</sub> measurements: explanation for an apparent missing oxidant?

“…NO x plays a central role in the chemistry of the troposphere, mainly through its impact on ozone (O 3 ) and hydroxyl (OH) radical concentrations. O 3 is a greenhouse gas (Wang et al, 1995) that adversely impacts human health (Mauzerall et al, 2005;Skalska et al, 2010) and leads to ecosystem damage (Ainsworth et al, 2012;Ashmore, 2005;Hollaway et al, 2012). It is produced through the reaction of peroxy radicals (HO 2 and RO 2 ) with NO (Dalsøren and Isaksen, 2006;Lelieveld et al, 2004).…”