Quantifying the contributions of individual NOx sources to the trend in ozone radiative forcing

Abstract

Source attribution of ozone radiative forcing (RF) is a prerequisite for developing adequate emission mitigation strategies with regards to climate impact. Decadal means of ozone fields from transient climate-chemistry simulations (1960e2019) are analysed and the temporal development of ozone RF resulting from individual NO x sources, e.g. road traffic, industry and air traffic, is investigated. We calculated an ozone production efficiency which is mainly dependent on the altitude of NO x emission and on the amount of background NO x with values varying over one order of magnitude. Air traffic and lightning are identified as NO x sources with a two and five times higher ozone production efficiency, respectively, than ground based sources. Second, radiative efficiency of source attributed ozone (i.e. total induced radiative flux change per column ozone) shows clear dependence on latitudinal structure of the ozone anomaly and, to a lesser extent, to its altitude. Lightning induced ozone shows the highest radiative efficiency because lightning primarily enhances ozone in low latitudes in the mid-troposphere (higher altitudes). Superimposed on these effects, a saturation effect causes a decreasing radiative efficiency with increasing background ozone concentrations. Changes in RF attributed to NO x induced ozone from 1960 to 2019 are controlled by three factors: changes in emissions, changes in ozone production efficiency and changes in the radiative efficiency. Leading effect is emission increase, but changes in ozone production efficiency increase ozone RF by a factor of three for air traffic, or reduce ozone RF by around 30% for ships. Additionally, changes in the radiative efficiency due to saturation effects change ozone RF by 2e5%.

Revisiting the contribution of land transport and shipping emissions to tropospheric ozone

“…To determine Dahlmann et al, 2011). The approach to calculate the RF by the results of the perturbation approach is similar to e.g.…”

“…Depending on the regime of the O 3 production and the strength of the perturbation in the individual regions, the O 3 production responds differently on emissions in the different regions (e.g., Dahlmann et al, 2011). To illustrate this in more detail, the dots in Fig.…”

“…Many of such investigations have been performed in the past to estimate the contribution of road traffic (but not the total land 20 transport effect, e.g., Granier and Brasseur, 2003;Niemeier et al, 2006;Matthes et al, 2007;Hoor et al, 2009;Koffi et al, 2010;Dahlmann et al, 2011;Grewe et al, 2012) and shipping (e.g. Lawrence and Crutzen, 1999;Eyring et al, 2007;Hoor et al, 2009;Koffi et al, 2010;Holmes et al, 2014) emissions to tropospheric ozone on the global scale.…”

Sensitivity of tropical tropospheric composition to lightning NOx production as determined by replay simulations with GEOS‐5

“…Lightning plays an important role with respect to climate, as LNO x production occurs primarily in the tropical UT, where O 3 acts most efficiently as a greenhouse gas [Lacis et al, 1990;Stockwell et al, 1999;Zhang et al, 2003;Kunhikrishnan and Lawrence, 2004;Dahlmann et al, 2011] and where high UV radiation, low background NO x , and long O 3 lifetime lead to very high O 3 production efficiency (approximately 100 molecules of O 3 per molecule of NO x ) [Dahlmann et al, 2011]. Conversely, lightning also influences the oxidative capacity and radiative forcing of the atmosphere through its effect on OH: increased LNO x promotes increased OH formation, which in turn oxidizes methane (a greenhouse gas) and leads to subsequent short-term radiative cooling [Kunhikrishnan and Lawrence, 2004].…”

Key drivers of ozone change and its radiative forcing over the 21st century

“…low background concentrations and longer 20 lifetimes of NO x , lower temperatures affecting ozone loss chemistry and abundant sunlight (e.g. Williams, 2005;Dahlmann et al, 2011). A small but significant fraction of lightning-induced NO x emissions are converted into less photochemically active nitric acid (HNO 3 , via HO 2 + NO reaction), which can be removed through wet deposition or transported into the lower stratosphere (acting as a reservoir of NO x ) 25 (e.g.…”