Aircraft Emissions Of Nitrogen Oxides Research Articles

Evaluation of aircraft emission at Tribhuvan international airport and its contribution to air quality in Kathmandu, Nepal

The recent rise in the number of aircraft flights and the subsequent increase in emissions has raised concerns worldwide, and this increasing trend is expected to continue. This research provides an overall estimation of the landing and take-off cycle (LTO) emissions from Tribhuvan International Airport (TIA) as well as the associated contribution of these emissions to ambient air quality in Kathmandu valley. The aircraft emissions of nitrogen oxides (NOx), carbon monoxide (CO), hydrocarbon (HC), sulfur dioxide (SO2), volatile organic compounds (VOCs), particulate matter (PM10, and PM2.5), and black carbon (BC) during the LTO are estimated for recent 20 years by using the emission factor method. The corresponding contribution to ambient air quality was simulated using AERMOD and Weather Research and Forecasting (WRF) models. The research reveals that total LTO emissions by aircraft at TIA range from 898 to 2123 tonnes per year (2000–2019). The average LTO emissions of NOx, CO, HC, VOC, SO2, PM10, PM2.5, and BC were around 14512, 8142, 2387, 1737, 1247, 481, 472, and 231 tonnes respectively during the period of 20 years. The highest aircraft emission was shown in taxi/idle mode for the LTO cycle, with major constituents being HC and CO. The LTO emissions and their effect on air quality have continually increased. The highest contribution of the LTO emissions on air quality was found in the pre-monsoon season. The dominant pollutants in TIA were nitrogen oxides and its average 24-h concentration was 158.1 μg/m3, which exceeded the National Ambient Air Quality Standard (NAAQS) limit value. Hence, LTO emission significantly contributed to ambient air quality in Kathmandu city.

Inverse modeling of Texas NO<sub>x</sub> emissions using space-based and ground-based NO<sub>2</sub> observations

Abstract. Inverse modeling of nitrogen oxide (NOx) emissions using satellite-based NO2 observations has become more prevalent in recent years, but has rarely been applied to regulatory modeling at regional scales. In this study, OMI satellite observations of NO2 column densities are used to conduct inverse modeling of NOx emission inventories for two Texas State Implementation Plan (SIP) modeling episodes. Addition of lightning, aircraft, and soil NOx emissions to the regulatory inventory narrowed but did not close the gap between modeled and satellite-observed NO2 over rural regions. Satellite-based top-down emission inventories are created with the regional Comprehensive Air Quality Model with extensions (CAMx) using two techniques: the direct scaling method and discrete Kalman filter (DKF) with decoupled direct method (DDM) sensitivity analysis. The simulations with satellite-inverted inventories are compared to the modeling results using the a priori inventory as well as an inventory created by a ground-level NO2-based DKF inversion. The DKF inversions yield conflicting results: the satellite-based inversion scales up the a priori NOx emissions in most regions by factors of 1.02 to 1.84, leading to 3–55% increase in modeled NO2 column densities and 1–7 ppb increase in ground 8 h ozone concentrations, while the ground-based inversion indicates the a priori NOx emissions should be scaled by factors of 0.34 to 0.57 in each region. However, none of the inversions improve the model performance in simulating aircraft-observed NO2 or ground-level ozone (O3) concentrations.

Prediction of the production of nitrogen oxide [formula omitted] in turbojet engines

Gaseous nitrogen oxides ( NO + NO 2 = NO x ) are known as atmospheric trace constituent. These gases remain a big concern despite the advances in low NO x emission technology because they play a critical role in regulating the oxidization capacity of the atmosphere according to Crutzen [1995. My life with O 3, NO x and other YZO x S; Nobel Lecture; Chemistry 1995; pp 195; December 8, 1995] . Aircraft emissions of nitrogen oxides ( NO x ) are regulated by the International Civil Aviation Organization. The prediction of NO x emission in turbojet engines by combining combustion operational data produced information showing correlation between the analytical and empirical results. There is close similarity between the calculated emission index and experimental data. The correlation shows improved accuracy when the 2124 experimental data from 11 gas turbine engines are evaluated than a previous semi empirical correlation approach proposed by Pearce et al. [1993. The prediction of thermal NO x in gas turbine exhausts. Eleventh International Symposium on Air Breathing Engines, Tokyo, 1993, pp. 6–9]. The new method we propose predict the production of NO x with far more improved accuracy than previous methods. Since a turbojet engine works in an atmosphere where temperature, pressure and humidity change frequently, a correction factor is developed with standard atmospheric laws and some correlations taken from scientific literature [Swartwelder, M., 2000. Aerospace engineering 410 Term Project performance analysis, November 17, 2000, pp. 2–5; Reed, J.A. Java Gas Turbine Simulator Documentation. pp. 4–5]. The new correction factor is validated with experimental observations from 19 turbojet engines cruising at altitudes of 9 and 13 km given in the ICAO repertory [Middleton, D., 1992. Appendix K (FAA/SETA). Section 1: Boeing Method Two Indices, 1992, pp. 2–3]. This correction factor will enable the prediction of cruise NO x emissions of turbojet engines at cruising speeds. The ICAO database [Goehlich, R.A., 2000. Investigation into the applicability of pollutant emission models for computer aided preliminary aircraft design, Book number 175654, 4.2.2000, pp. 57–79] can now be completed using the approach we propose to complete the whole mission flight NO x emissions.

Aircraft induced effects on Arctic polar stratospheric cloud formation

Stratospheric chemical transport models (CTM) have been used to calculate perturbations in HNO 3 and H 2 O due to stratospheric supersonic aircraft emissions of nitrogen oxides and water vapour. The perturbations were used as input to a detailed microphysical model to study the effects on Arctic polar stratospheric cloud (PSC) formation. Actual winter 1989/90 temperature histories from domain filling trajectories were used to calculate PSC particle types and surface areas, allowing the inherent temperature hysteresis in the life cycles of different PSC particle types to be taken into account. Increased concentrations of water vapour, caused by stratospheric aircraft emissions, imply higher freezing temperatures for ice in supercooled ternary solution liquid type PSC particles, required for the formation of solid type PSCs. A potential exists that the enhanced H 2 O concentrations may lead to more solid type PSC formation and thereby more widespread denitrification.

A 3D chemistry transport model study of changes in atmospheric ozone due to aircraft NO x emissions

The effect of present day aircraft emissions of nitrogen oxides (NO x = NO + NO 2) on atmospheric NO x and ozone concentrations is investigated with the global three-dimensional chemistry transport model CTMK. This model uses 12-hourly meteorological data from the ECMWF analysis and includes parameterizations for subgrid scale processes such as convection. CTMK includes an ozone chemistry module containing the methane and carbon monoxide oxidation chain for the troposphere and lower stratosphere. It is found by using the ANCAT aircraft NO x emission invertory that aviation contributes to 20–100 pptv of the NO x at cruise altitudes in northern mid-latitudes, which corresponds to 30–80 and 20–50% of the background mixing ratios for January and July, respectively. This perturbation in NO x occurs mainly in the North Atlantic Flight Corridor and is transported eastwards. The resulting increase in upper tropospheric ozone is 2–3 ppbv (2%) in January and 5–10 ppbv (3%) in July. The ozone perturbation is almost zonally symmetric and attains maximum values at northern mid-latitudes in January and in the polar region in July. The calculated effect of aircraft emissions is found to be small (i.e. less than 5 pptv for NO x and less than 1 ppbv for 0 3) in the southern hemisphere. The perturbation of NO x by the aircraft emissions at cruise altitudes in northern mid-latitudes is large compared to the standard deviation. Therefore, it is expected that the effect of aviation on NO x is distinguishable from the contribution from other NO x sources. As the modelled natural variability of ozone is already about 30%, it will not be easy to detect the ozone perturbation due to aircraft NO x emissions.

The passive transport of NO x emissions from aircraft studied with a hierarchy of models

The passive transport of aircraft emissions of nitrogen oxides (NO x = NO + NO 2) has been studied with a hierarchy of models ranging from two-dimensional and three-dimensional chemistry transport models up to three-dimensional models of the general circulation. The sink of NO x was parameterized by an exponential decay process with a globally constant half-lifetime of 10 days. By performing a simple experiment the importance of the various transport processes has been studied. The three-dimensional models show that the monthly mean volume mixing ratio of NO x varies by a factor of three in the longitudinal direction and the temporal variability is of the order of 30%. In view of the nonlinearity of the chemical processes leading to ozone formation in the presence of NO x this implies that the assessment of the effects of subsonic aircraft emissions of NO x should be done with three-dimensional models. Vertical redistribution by convection strongly affects the maximum NO x mixing ratio at cruise altitudes, but due to the limited lifetime of NO x of the order of ten days the most important contribution to the mixing ratio at a certain level usually stems from emissions around that level. The strong static stability in the stratosphere hampers significant dispersion of the subsonic aircraft emissions above the height where the emissions take place for the lifetimes considered here. Some model deficiencies and biases have been identified and discussed. Examples are the oscillatory signature of NO x distributions obtained with a spectral advection scheme, the strong diffusion of one of the GCMs into the polar regions, and the too intense interhemispheric exchange of one of the two-dimensional CTMs. For the vertical redistribution of the emissions it may be necessary to include not only updrafts but also downdrafts in the convective parametrization of the transport model.

Impact of present aircraft emissions of nitrogen oxides on tropospheric ozone and climate forcing

A two‐dimensional (2‐D) model in which dynamics, radiation and chemistry are treated interactively is used to investigate the seasonal changes in tropospheric ozone due to current nitrogen oxide emissions from aircraft and to assess the associated radiative forcing on the climate system. Our results confirm the high efficiency of nitrogen oxide in‐situ emissions in producing ozone in comparison to surface emissions. The ozone increase is characterized by a strong seasonal variation; it reaches more than 7% during summer in the upper troposphere at northen mid‐latitudes. On a global average basis, the radiative forcing associated with this ozone increase appears to be small in comparison to that of other greenhouse gases. However, it may play a significant role in the anthropogenic forcing on northern hemisphere climate.

Impact of aircraft and surface emissions of nitrogen oxides on tropospheric ozone and global warming

ACTUAL and potential increases in aircraft traffic are causing concern about the effects of aircraft exhaust emission on atmos-pheric chemistry. Model results1–3 and measurements4–6 in the Northern Hemisphere have shown that growth in surface emissions of nitrogen oxides and hydrocarbons leads to increases in concentration of tropospheric ozone. Tropospheric ozone is toxic to plants, humans and other organisms, and it is a greenhouse gas7–9. The radiative forcing of surface temperature is most sensitive to changes in tropospheric ozone at a height of ∼12 km (ref. 8), where aircraft emissions of nitrogen oxides are at a maximum and where the model sensitivity of ozone to nitrogen oxide emissions is enhanced. Our model results show that the radiative forcing of surface temperature is about thirty times more sensitive to aircraft emissions of nitrogen oxides than to surface emissions. We also find that the impact on global warming of increases in tropospheric ozone caused by increases in surface emissions of nitrogen oxides has previously been overestimated by a factor of five1,10, owing to an error in the calculation of the ozone budget.