Emissions aircraft

GrooB, J.-U., C. Bruhl, and T. Peter, Impact of Aircraft Emissions on Tropospheric and Stratospheric Ozone. Part I Chemistry and 2-D Model Results, Atmos. Em iron., 32, 3173-3184 (1998). 

Karcher et al. (1996) suggest that this additional oxidation occurs on the soot particles that have been observed in the stratosphere and attributed to aircraft emissions (Pueschel et al., 1992a Blake and Kato, 1995). The oxidation of S02 on soot particles is known to occur in the troposphere as well (see Chapter 8.C.4). If the same is true of the exhaust from HSCTs, their emissions could lead to significant increases in both the number of particles in the lower stratosphere and as their associated surface area. 

Weaver, C. J., A. R. Douglass, and D. B. Considine, A 5-Year Simulation of Supersonic Aircraft Emission Transport Using a Three-Dimensional Model, J. Geophys. Res., 101, 20975-20984 (1996). 

GLOBAL IMPACT OF AIRCRAFT EMISSION ON OZONE CONCENTRATIONS AND METHANE LIFETIME RESULTS FROM THE 1999IPCC AIRCRAFT ASSESSMENT... 

There are two main reasons why aircraft emissions are important. 

Firstly air traffic and the emission of pollutants from air traffic have increased rapidly over the last two to three decades, and the prognosis for future emissions indicate continued rapid increases over several decades to come. What is particular significant is that the increase is expected to be much larger than the general emission of pollutants. This means that we should expect the impact of aircraft emissions on the environment to become more important in the future than it is today. An obvious consequence of this is that good prognosis of future aircraft emissions are essential for performing reliable future estimates of aircraft emissions. 

In this paper we will focus on the most recent extensive study performed as part of the IPCC assessment of aircraft impact (IPCC, 1999). In this study a thorough evaluation of current and future aircraft emissions were performed, and several modelling groups participated in model predictions and modelling comparisons of future aircraft impact. 

Table 1. Adopted global aircraft emissions of NOx for selected years.

The basic scenarios examine some of the important aspects in understanding the calculated environmental impact of aircraft. However, a number of uncertainties remain in the treatment of chemical and physical processes that may influence the effects from aircraft emissions. A series of special sensitivity calculations were therefore designed to investigate the most important of the recognised uncertainties. The subsonic aircraft sensitivity scenarios, as described later, examine uncertainties in the background atmosphere, the treatment of upper tropospheric and lower stratospheric chemical and dynamical processes, and the different analyses of aircraft emissions. 

For the time slices 1992 and 2015, two model runs were made A basic scenario with no aircraft emissions, and a scenario with aircraft NOx emissions added (Table 1). For 2050 a model run with a basic scenario and two aircraft runs with the medium and high scenarios were run (Table 1). The model runs are summarised in Table 3. 

Table 3. Base background scenarios and subsonic aircraft NOx scenarios used in the global model studies. These scenarios are used to study ozone increases, non linearity in ozone productions from aircraft emissions and the impact on methane lifetime and methane concentrations for future aircraft emissions.

Most of the aircraft emissions occur in particular regions determined by the main flight corridors. Up to present time, these emissions have basically been over Europe and the US, and over the North Atlantic along the flight corridor for traffic between Europe and the US. Towards 2015 significant increases in traffic between Europe and South East Asia and between the US and South East Asia is expected to occur. 

The significance of these factors for ozone is explored by the model studies of current and future aircraft emissions. 

In the IPCC (1999) aircraft impact study six global models were used for the prediction of current and future impact of aircraft emissions. The six models and the references to a detailed description of the models is given in Table 4 below ... 

One clear limitation of most of the models is that they have little or no representation of explicit stratospheric chemistry. This could also clearly limit the models ability to predict the full atmospheric impact on ozone of aircraft emissions since it is predicted by the models that approximately 1/3 of the ozone perturbations occur in the lower stratosphere. 

There may be a strong seasonal cycle in the calculated impact of aircraft emissions on ozone. For example, using the same emission scenarios, the UIO and the UKMO models calculate a 40% larger increase of ozone in the NH in April compared to July (Stevenson et al. 1997 Bemtsen and lsaksen, 1998). Other models find much weaker seasonal cycles (e.g. IMAGES/BISA and ECHAM3/CHEM), or find the maximum increases in summer (e.g. TM3 and HARVARD). The reasons for these seasonal differences are probably associated with the different background NOx conditions in the different models (see next section). 

Figure 1. Annual (2015) and zonal average increases of ozone volume mixing ratios due to aircraft emissions [ppbv] calculated by six 3-D models. The IMAGES/BISA model does not give results above 14 km, and the HARVARD model does not give results above 12 km.

Table 5. Atmospheric ozone increases from aircraft emission per NOx molecule emitted, relative to the increase in 1992. The emissions of NOx are die same as given in Table l.The values represent increases in global ozone concentrations from the Earth s surface to 16 km and is the average increase for the models that participated in the model studies given in Table 4.

Table 6. Calculated change in methane lifetime from aircraft emissions up to 300 hPa ( 10 km).

Brasseur, G. P., R. A. Cox, D. Hauglustaine, I. Isaksen, J. Lelieveld, D. H. Lister, R. Sausen, U. Schumann, A. Wahner, and P. Wiesen, 1998 European scientific assessment of the atmospheric effects of aircraft emissions, Atmos. Environ., 32,2329-2418. 

Abstract. The impact of future aircraft emissions on concentrations of reactive nitrogen, water vapour and ozone has been calculated using the 3-dimensional stratospheric chemical transport model SCTM-1. Emissions of NOx (N0+N02) and H20 from both sub- and supersonic aircraft have been considered. 

NOx emissions from subsonic aircraft flying in the troposphere and the lowermost stratosphere lead to a significant increase in ozone in the upper troposphere. Emissions of NOx and H20 from supersonic aircraft cruising in the stratosphere are calculated to decrease the column abundance of O3. The effects of aircraft emissions are found to be strongly dependent on flight altitudes and on assumed emission indices for NOx. 

The scenarios for aircraft emissions are from the NASA data base [1]. Emissions of NOx and water vapour from sub- and supersonic aircraft were considered. For the projected fleet of 500 supersonic aircraft, different emission indices for NOx and cruising altitudes were assumed. 

All figures addressed in the following show modeled perturbations with respect to the reference case without any aircraft emissions (termed NoAircraft ). 

The effects of aircraft emissions on NOy and H2O are much larger over the Northern than over the Southern Hemisphere in line with the air traffic patterns. 

The model results obtained in this study suggest that future aircraft emissions will have a significant impact on levels of NOx, stratospheric water vapor, and ozone in both the troposphere and the stratosphere. The effect of future supersonic aircraft depends strongly on the cruising altitude assumed for the supersonic fleet. 

Baughcum, S. L., and Henderson, S. C. (1998) Aircraft Emission Scenarios Projected in Year 2015 for the NASA Technology Concept Aircraft (TCA) High Speed Civil Transport. NASA-CR-1998-207635. 

ATMOSPHERIC OZONE AS A CLIMATE GAS STUDIES CONCERNING AIRCRAFT EMISSIONS... 

Radiative Forcing Associated with Aircraft Emissions... 

The results presented here focus on the present and future effect on radiative forcing due to changes in the radiatively-important chemical species (03, water vapor and CHJ associated with aircraft emissions. To address this question, we conduct uncoupled model experiments using the University of Oslo (UiO) 3-D chemical transport models (CTMs) to calculate changes in atmospheric composition and the State University of New York at Albany (SUNYA) 3-D global climate model (GCM) to calculate the radiative forcing associated with these changes. Two case studies were conducted to... 

FIGURE 1. UiO-CTM calculated changes (%) in geographical distribution of 320 hPa 03 and tropospheric 03 column due to aircraft emissions. 

TABLE 3. The effect on radiative forcing (Wm J) due to changes in 0, and CH, associated with subsonic aircraft emissions. 

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