The role of plume-scale processes in long-term impacts of aircraft emissions

Emissions from aircraft engines contribute to atmospheric NOx, driving changes in both the climate and in surface air quality. Existing atmospheric models typically assume instant dilution of emissions into large-scale grid cells, neglecting non-linear, small-scale processes occurring in aircraft wakes. They also do not explicitly simulate the formation of ice crystals, which could drive local chemical processing. This assumption may lead to errors in estimates of aircraft-attributable ozone production, and in turn to biased estimates of aviation's current impacts on the atmosphere and the effect of future changes in emissions. This includes black carbon emissions, on which contrail ice forms. These emissions are expected to reduce as biofuel usage increases, but their chemical effects are not well captured by existing models. To address this problem, we develop a Lagrangian model that explicitly models the chemical and microphysical evolution of an aircraft plume. It includes a unified tropospheric-stratospheric chemical mechanism that incorporates heterogeneous chemistry on background and aircraft-induced aerosols. Microphysical processes are also simulated, including the formation, persistence, and chemical influence of contrails. The plume model is used to quantify how the longterm (24 h) atmospheric chemical response to an aircraft plume varies in response to different environmental conditions, engine characteristics, and fuel properties. We find that an instant-dilution model consistently overestimates ozone production compared to the plume model, up to a maximum error of ~ 200 % at cruise altitudes. Instant dilution of emissions also underestimates the fraction of remaining NOx, although the magnitude and sign of the error vary with season, altitude, and latitude. We also quantify how changes in black carbon emissions affect plume behavior. Our results suggest that a 50 % reduction in black carbon emissions, as may be possible through blending with certain biofuels, may lead to thinner, shorter-lived contrails. For the cases that we modeled, these contrails sublimate ∼ 5 % to 15 % sooner and are 10 % to 22 % optically thinner. The conversion of emitted NOx to HNO3 and N2O5 falls by 16 % and 33 %, respectively, resulting in chemical feedbacks that are not resolved by instant-dilution approaches. The persistent discrepancies between results from the instant-dilution approach and from the aircraft plume model demonstrate that a parameterization of effective emission indices should be incorporated into 3-D atmospheric chemistry transport models.NASA Glenn Research Center (Grant NNX14AT22A

Identifying the ozone-neutral aircraft cruise altitude

Depletion of stratospheric ozone, and the associated increase in population exposure to UV radiation, is an environmental consequence of high-altitude, supersonic aviation. Assessments of the impacts of emissions from subsonic aircraft – which fly at lower altitudes – have instead shown that they produce a net increase, rather than decrease, in global net ozone, suggesting the existence of an intermediate “column ozone neutral” cruise altitude. Knowing this altitude and its variation with factors such as latitude, season, and fuel composition could provide a pathway towards reducing the environmental impacts of aviation, but would require a prohibitive number of atmospheric simulations. We instead use the newly developed GEOS-Chem tropospheric-stratospheric adjoint to identify the location of the column ozone-neutral aircraft cruise altitude as a function of these factors. We show that, although the mean ozone neutral altitude is at 13.5 km globally, this varies from 14.6 km to 12.5 km between the equator and 60°N. This altitude varies by less than a kilometer between seasons, but the net depletion resulting from flying at greater altitudes varies by a factor of two. We also find that eliminating fuel sulfur would result in a neutral altitude 0.5–1.0 km greater than when conventional jet fuel is burned. Our results imply that a low Mach number supersonic aircraft burning low-sulfur fuel (e.g. biofuels) may be able to achieve net zero global ozone change. However, for a fleet to achieve ozone neutrality will require careful consideration of the non-linear variation in sensitivity with altitude and latitude.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Aircraft Noise and Climate Effect

SCOPE11 Method for Estimating Aircraft Black Carbon Mass and Particle Number Emissions

Black carbon (BC) emissions from aircraft engines lead to an increase in the atmospheric burden of fine particulate matter (PM2.5). Exposure to PM2.5 from sources, including aviation, is associated with an increased risk of premature mortality, and BC suspended in the atmosphere has a warming impact on the climate. BC particles emitted from aircraft also serve as nuclei for contrail ice particles, which are a major component of aviation’s climate impact. To facilitate the evaluation of these impacts, we have developed a method to estimate BC mass and number emissions at the engine exit plane, referred to as the Smoke Correlation for Particle EmissionsCAEP11 (SCOPE11). We use a data set consisting of SN–BC mass concentration pairs, collected using certification-compliant measurement systems, to develop a new relationship between smoke number (SN) and BC mass concentration. In addition, we use a complementary data set to estimate measurement system loss correction factors and particle geometric mean diameters to estimate BC number emissions at the engine exit plane. Using this method, we estimate global BC emissions from aircraft landing and takeoff (LTO) operations for 2015 to be 0.74 Gg/year (95% CI = 0.64–0.84) and 2.85 × 1025 particles/year (95% CI = 1.86–4.49 × 1025)

Impacts of a Near-Future Supersonic Aircraft Fleet on Atmospheric Composition and Climate

13-C-AJFF-MIT-059 , 064This is an open access article under the terms of the Creative Commons Attribution 3.0 Unported (CC BY 3.0) license https://creativecommons.org/licenses/by/3.0/. Please cite this article as: Eastham, SD; Fritz, T; Sanz-Mor\ue8re, I; Prashanth, P; Allroggen, F; Prinn, RG; Speth, RL; Barrett, SRH. 2022. Impacts of a near-future supersonic aircraft fleet on atmospheric composition and climate. Environmental Science: Atmospheres. https://doi.org/10.1039/D1EA00081KSupersonic aircraft will have environmental impacts distinct from those of subsonic aviation, and are once again being developed and bought. Assessments of supersonic aircraft emissions impacts over the last decade have focused on the ozone and climate impacts of nitrogen oxides and water vapor, but assumed zero-sulfur fuel, zero black carbon emissions, and neglect likely design constraints on near-future engine technology. We assess the impacts on atmospheric composition and non-CO2 climate forcing of a near-future supersonic aircraft fleet with current-generation engine technology burning fossil-based kerosene fuel with current-day sulfur content. Using vehicle performance modeling, market demand projection and global atmospheric chemistry-transport modeling, we find that a supersonic fleet flying at Mach 1.6 and 15\u201317 km altitude, burning 19 Tg of fuel each year and emitting 170 Gg of NOx would cause a 0.046% reduction in global column ozone. We estimate the radiative forcing (climate impact) from changes in atmospheric concentrations of ozone (2.9 mW m-2), water vapor (1.3 mW m-2), carbonaceous and inorganic aerosols (-6.6 mW m-2), and methane (-0.65 mW m-2), resulting in a net non-CO2, non-contrail forcing of -3.5 mW m-2 and varying from -3.0 to -3.9 mW per m2 per year to year. We also show that the use of zero-sulfur fuel would halve net ozone depletion but increases the net non-CO2 non-contrail forcing to +2.8 mW m-2 due to the loss of a cooling effect from sulfate aerosols. A smaller fleet of Mach 2.2 aircraft flying at 18\u201320 km and burning 14 Tg of fuel but emitting twice as much NOx per unit of fuel results in 17 times as much net ozone depletion. The net radiative forcing for this fleet is of uncertain sign, averaging -0.15 mW m-2 but varying between -3.2 and +2.0 mW per m2 per year to year. Our results show that assessments of near-future supersonic aviation must consider the effects of fuel sulfur and black carbon alongside emissions of water vapor, NOx, and CO2, and that the net environmental impacts will be a trade-off between competing environmental concerns

Nitrogen oxides in the free troposphere : Implications for tropospheric oxidants and the interpretation of satellite NO2 measurements

Satellite-based retrievals of tropospheric NO2 columns are widely used to infer NOx (gNOg+gNO2) emissions. These retrievals rely on model information for the vertical distribution of NO2. The free tropospheric background above 2gkm is particularly important because the sensitivity of the retrievals increases with altitude. Free tropospheric NOx also has a strong effect on tropospheric OH and ozone concentrations. Here we use observations from three aircraft campaigns (SEAC4RS, DC3, and ATom) and four atmospheric chemistry models (GEOS-Chem, GMI, TM5, and CAMS) to evaluate the model capabilities for simulating NOx in the free troposphere and attribute it to sources. NO2 measurements during the Studies of Emissions and Atmospheric Composition, Clouds, and Climate Coupling by Regional Surveys (SEAC4RS) and Deep Convective Clouds and Chemistry (DC3) campaigns over the southeastern U.S. in summer show increasing concentrations in the upper troposphere above 10gkm, which are not replicated by the GEOS-Chem, although the model is consistent with the NO measurements. Using concurrent NO, NO2, and ozone observations from a DC3 flight in a thunderstorm outflow, we show that the NO2 measurements in the upper troposphere are biased high, plausibly due to interference from thermally labile NO2 reservoirs such as peroxynitric acid (HNO4) and methyl peroxy nitrate (MPN). We find that NO2 concentrations calculated from the NO measurements and NO-NO2 photochemical steady state (PSS) are more reliable to evaluate the vertical profiles of NO2 in models. GEOS-Chem reproduces the shape of the PSS-inferred NO2 profiles throughout the troposphere for SEAC4RS and DC3 but overestimates NO2 concentrations by about a factor of 2. The model underestimates MPN and alkyl nitrate concentrations, suggesting missing organic NOx chemistry. On the other hand, the standard GEOS-Chem model underestimates NO observations from the Atmospheric Tomography Mission (ATom) campaigns over the Pacific and Atlantic oceans, indicating a missing NOx source over the oceans. We find that we can account for this missing source by including in the model the photolysis of particulate nitrate on sea salt aerosols at rates inferred from laboratory studies and field observations of nitrous acid (HONO) over the Atlantic. The median PSS-inferred tropospheric NO2 column density for the ATom campaign is 1.7g±g0.44g×g1014gmolec.gcm-2, and the NO2 column density simulated by the four models is in the range of 1.4-2.4g×g1014gmolec.gcm-2, implying that the uncertainty from using modeled NO2 tropospheric columns over clean areas in the retrievals for stratosphere-troposphere separation is about 1g×g1014gmolec.gcm-2. We find from GEOS-Chem that lightning is the main primary NOx source in the free troposphere over the tropics and southern midlatitudes, but aircraft emissions dominate at northern midlatitudes in winter and in summer over the oceans. Particulate nitrate photolysis increases ozone concentrations by up to 5gppbv (parts per billion by volume) in the free troposphere in the northern extratropics in the model, which would largely correct the low model bias relative to ozonesonde observations. Global tropospheric OH concentrations increase by 19g%. The contribution of the free tropospheric background to the tropospheric NO2 columns observed by satellites over the contiguous U.S. increases from 25g±g11g% in winter to 65g±g9g% in summer, according to the GEOS-Chem vertical profiles. This needs to be accounted for when deriving NOx emissions from satellite NO2 column measurements

The complete sequence of a human Y chromosome.

The human Y chromosome has been notoriously difficult to sequence and assemble because of its complex repeat structure that includes long palindromes, tandem repeats and segmental duplications1-3. As a result, more than half of the Y chromosome is missing from the GRCh38 reference sequence and it remains the last human chromosome to be finished4,5. Here, the Telomere-to-Telomere (T2T) consortium presents the complete 62,460,029-base-pair sequence of a human Y chromosome from the HG002 genome (T2T-Y) that corrects multiple errors in GRCh38-Y and adds over 30 million base pairs of sequence to the reference, showing the complete ampliconic structures of gene families TSPY, DAZ and RBMY; 41 additional protein-coding genes, mostly from the TSPY family; and an alternating pattern of human satellite 1 and 3 blocks in the heterochromatic Yq12 region. We have combined T2T-Y with a previous assembly of the CHM13 genome4 and mapped available population variation, clinical variants and functional genomics data to produce a complete and comprehensive reference sequence for all 24 human chromosomes

The complete sequence of a human Y chromosome

The human Y chromosome has been notoriously difficult to sequence and assemble because of its complex repeat structure that includes long palindromes, tandem repeats and segmental duplications1-3. As a result, more than half of the Y chromosome is missing from the GRCh38 reference sequence and it remains the last human chromosome to be finished4,5. Here, the Telomere-to-Telomere (T2T) consortium presents the complete 62,460,029-base-pair sequence of a human Y chromosome from the HG002 genome (T2T-Y) that corrects multiple errors in GRCh38-Y and adds over 30 million base pairs of sequence to the reference, showing the complete ampliconic structures of gene families TSPY, DAZ and RBMY; 41 additional protein-coding genes, mostly from the TSPY family; and an alternating pattern of human satellite 1 and 3 blocks in the heterochromatic Yq12 region. We have combined T2T-Y with a previous assembly of the CHM13 genome4 and mapped available population variation, clinical variants and functional genomics data to produce a complete and comprehensive reference sequence for all 24 human chromosomes

The complete sequence of a human genome.

Since its initial release in 2000, the human reference genome has covered only the euchromatic fraction of the genome, leaving important heterochromatic regions unfinished. Addressing the remaining 8% of the genome, the Telomere-to-Telomere (T2T) Consortium presents a complete 3.055 billion-base pair sequence of a human genome, T2T-CHM13, that includes gapless assemblies for all chromosomes except Y, corrects errors in the prior references, and introduces nearly 200 million base pairs of sequence containing 1956 gene predictions, 99 of which are predicted to be protein coding. The completed regions include all centromeric satellite arrays, recent segmental duplications, and the short arms of all five acrocentric chromosomes, unlocking these complex regions of the genome to variational and functional studies