602 research outputs found
Impact of climate variability on tropospheric ozone
No full textA simulation with the climate–chemistry model (CCM) E39/C is presented, which covers both the troposphere and stratosphere
dynamics and chemistry during the period 1960 to 1999. Although the CCM, by its nature, is not exactly representing observed
day-by-day meteorology, there is an overall model's tendency to correctly reproduce the variability pattern due to an inclusion of
realistic external forcings, like observed sea surface temperatures (e.g. El Niño), major volcanic eruption, solar cycle,
concentrations of greenhouse gases, and Quasi-Biennial Oscillation. Additionally, climate–chemistry interactions are included, like
the impact of ozone, methane, and other species on radiation and dynamics, and the impact of dynamics on emissions (lightning).
However, a number of important feedbacks are not yet included (e.g. feedbacks related to biogenic emissions and emissions due to
biomass burning). The results show a good representation of the evolution of the stratospheric ozone layer, including the ozone
hole, which plays an important role for the simulation of natural variability of tropospheric ozone. Anthropogenic NOx emissions
are included with a step-wise linear trend for each sector, but no interannual variability is included. The application of a number of
diagnostics (e.g. marked ozone tracers) allows the separation of the impact of various processes/emissions on tropospheric ozone
and shows that the simulated Northern Hemisphere tropospheric ozone budget is not only dominated by nitrogen oxide emissions
and other ozone pre-cursors, but also by changes of the stratospheric ozone budget and its flux into the troposphere, which tends to
reduce the simulated positive trend in tropospheric ozone due to emissions from industry and traffic during the late 80s and early
90s. For tropical regions the variability in ozone is dominated by variability in lightning (related to ENSO) and stratosphere–
troposphere exchange (related to Northern Hemisphere Stratospheric dynamics and solar activity). Since tropospheric background
chemistry is regarded only, the results are quantitatively limited with respect to derived trends. However, the main results are
regarded to be robust.
Although the horizontal resolution is rather coarse in comparison to regional models, such kind of simulations provide useful
and necessary information on the impact of large-scale processes and inter-annual/decadal variations on regional air quality
Simulation of Stratospheric Water Vapor Trends: Impact on Stratospheric Ozone Chemistry
No full textA transient model simulation of the 40-year time
period 1960 to 1999 with the coupled climate-chemistry
model (CCM) ECHAM4.L39(DLR)/CHEM shows a stratospheric
water vapor increase over the last two decades of
0.7 ppmv and, additionally, a short-term increase after major
volcanic eruptions. Furthermore, a long-term decrease in
global total ozone as well as a short-term ozone decline in the
tropics after volcanic eruptions are modeled. In order to understand
the resulting effects of the water vapor changes on
lower stratospheric ozone chemistry, different perturbation
simulations were performed with the CCM ECHAM4.L39-
(DLR)/CHEM feeding the water vapor perturbations only to
the chemistry part. Two different long-term perturbations of
lower stratospheric water vapor, +1 ppmv and +5 ppmv, and a
short-term perturbation of +2 ppmv with an e-folding time of
two months were applied. An additional stratospheric water
vapor amount of 1 ppmv results in a 5–10% OH increase in
the tropical lower stratosphere between 100 and 30 hPa. As
a direct consequence of the OH increase the ozone destruction
by the HOx cycle becomes 6.4% more effective. Coupling
processes between the HOx-family and the NOx/ClOxfamily
also affect the ozone destruction by other catalytic
reaction cycles. The NOx cycle becomes 1.6% less effective,
whereas the effectiveness of the ClOx cycle is again
slightly enhanced. A long-term water vapor increase does
not only affect gas-phase chemistry, but also heterogeneous
ozone chemistry in polar regions. The model results indicate
an enhanced heterogeneous ozone depletion during antarctic
spring due to a longer PSC existence period. In contrast,
PSC formation in the northern hemisphere polar vortex and
therefore heterogeneous ozone depletion during arctic spring
are not affected by the water vapor increase, because of the
less PSC activity. Finally, this study shows that 10% of the
global total ozone decline in the transient model run can
be explained by the modeled water vapor increase, but the
simulated tropical ozone decrease after volcanic eruptions is
caused dynamically rather than chemically
A trans-splicing group I intron and tRNA-hyperediting in the mitochondrial genome of the lycophyte Isoetes engelmannii
No full textGrewe F, Viehöver P, Weisshaar B, Knoop V. A trans-splicing group I intron and tRNA-hyperediting in the mitochondrial genome of the lycophyte Isoetes engelmannii. Nucleic Acids Research. 2009;37(15):5093-5104
Green Flight Trajectories: A REACT4C data analysis
No full textREACT4C is a project that received European funding to investigate whether air traffic across the North Atlantic Ocean can be rerouted such that the resulting climate impact is reduced. The project considered 400 daily flights in each direction. Eight frequently occurring weather situations were identified, based on the strength and location of the jet stream between North America and Europe. It was found that the climate impact could be reduced to a large extent, although the impact reduction potential heavily depends on the direction of flight, the weather pattern under consideration, the climate metric used to quantify climate impact, and the relative importance of climate impact and economic cost during the optimization. The way in which climate-optimal trajectories compare to their cost-optimal counterparts, is still largely unknown. This research examines how the routes are affected by the climate optimization. Two kinds of studies are performed. The first one is a case study, in which the trajectories of one combination of direction, climate metric, weather type and level of climate optimization are compared with the cost- optimal routes. The influence of each of these four case differentiators on the flights is examined as well, using a one-factor-at-a-time approach. A tool is made that can be used to analyze the trajectories of any combination of flight direction, climate metric, weather pattern and level of climate optimization. The second study is a general analysis of the REACT4C routes, taking into account all combinations of the four case differentiators. This study is conducted to unravel general trends in the way direction, metric, weather and level of climate optimization influence the way in which flights are rerouted. The following characteristics are used to quantify how routes are altered. First, the percentage of affected flights is determined. Then, the flight duration and flight distance increments with respect to the cost-optimized flights are computed. Furthermore, the shift in latitude and altitude is also considered. Finally, frequently occurring rerouting schemes are identified, and the percentage of flights belonging to each scheme is determined. It was found in both the case study and the general analysis that the way in which climate-optimized routes compare to their cost-optimized counterparts, highly depends on the direction of flight, the weather pattern and the relative importance of economic cost and climate impact during the optimization. However, the choice of climate metric proved to have hardly any influence on the rerouting strategies. Because of the substantial cross-case differences, the preferred strategy to investigate rerouting characteristics is by making use of the case analysis tool that was created. Nonetheless, the general study unravelled some general trends. The trajectories in general are altered such that the flight duration and flight distance are increased, and the cruise altitude is lowered. Furthermore, generally there are more shifts towards the south than there are towards the north. Increasing the level of climate optimization is shown to result into more extreme route alterations. Flights towards Europe are in general more often north of the original routes than in westbound direction. The climate metric used during the optimization has little to no influence on the way the routes are changed. Finally, no trends in trajectory alterations are distinguishable between the eight weather patterns.Aerospace EngineeringControl & OperationsAircraft Noise & Climate Effects (ANCE
Analysis of driving parameters for green flight trajectories
No full textClimate change is an important problem nowadays. There are several industries causing this problem. One of them is the air transport industry. In order to reduce its induced climate impact there are different approaches: design of new aircrafts or engines, use of alternative fuels, more efficient air traffic management, or re-routing. All of them except re-routing aim on reducing carbon dioxide emissions. Re-routing, on the other hand, aims on reducing the climate impact of non-CO2 emissions (that considerably alter their climate impact depending on the region of the atmosphere where they are released) by increasing slightly the carbon dioxide emissions. This study focuses on this last approach. It establishes an analysis of the results obtained within the REACT4C project (Reducing Emissions from Aviation by Changing Trajectories for the benefit of Climate). The project aims to reduce aircraft induced climate impact in the North Atlantic flight corridor by changes in flight trajectories and considers fleets of around 400 aircraft. Moreover, this project considers eight different weather patterns (three for summer and five for winter), two flight directions (westbound and eastbound), and three climate metrics. Therefore, a total of 48 configurations have to be studied. Moreover it considers six different climate parameters causing the total climate impact. The climate parameters are carbon dioxide, water vapor, contrails, and NOx. The NOx climate impact is obtained as the summation of ozone, methane, and primary mode ozone climate impacts. The results that are analyzed are the climate impact caused by each of the climate parameters and how this climate impact changes when applying gradual changes on the aircraft trajectories. The analysis shows that water vapor has a negligible effect on climate impact. Carbon dioxide climate impact is more relevant when considering long term time horizons. Also, it increases when more trajectories are modified since the fuel consumption increases. Contrails are the main driver of the optimization for seven out of eight weather patterns. Their climate impact goes down during the optimization. Moreover, they are more important when considering short term time horizons and westbound flights. NOx is driving the optimization for only one weather pattern. Its contribution to reduce the total climate impact during the optimization is higher in the long term due to the enhanced net-cooling effect caused by methane depletion. Moreover, it is more important for eastbound flights. However, for winter weather patterns, NOx is controlled mainly by methane and primary mode ozone during most part of the optimization. Ozone is only important in the first and last segments. In addition, ozone presents the highest values of climate impact and has more contribution in the short term; while methane has always a negative climate impact or net-cooling effect due to its depletion, and is more important in the long term. The climate impact reduction is caused in the first part of the optimization by a small number of flights that reduce considerably their climate impact. Their trajectories change to go through regions of the atmosphere where their climate impact is smaller. As the optimization progresses, there are more flights modifying their routes. However, their climate impact reduction is not as noticeable as in the first cases. This happens because the regions of the atmosphere where the emissions have a lower climate impact are busier with the prior flights. Therefore the latter flights changing their trajectories have less potential to reduce their climate impact. This leads to a small part of the fleet causing an important climate impact reduction while the vast majority of flights slightly reduce their climate impact.Aerospace EngineeringControl & OperationsAircraft Noise and Climate Effects (ANCE
Comparison between global models and measurements of trace gases during TROCCINOX
No full textAirborne trace gas measurements carried out over southern Brazil during TROCCINOX-1 with the Falcon aircraft are compared to results from three global models: ECHAM, MATCH and TM4. The agreement between the models, with different parameterizations for lightning-produced NOX (=NO+NO2), and the measurements is investigated along single flight tracks. A new parameterization based on the mass flux in the updrafts [Grewe et al., 2001; Kurz and Grewe, 2002] shows promising results in comparison to the more commonly used parameterization based on the cloud top height [Price and Rind, 1992]. The most realistic model results for the total amount of lightning-produced NOX on the global scale were achieved with 5 Tg(N) yr-1
Aviation H2O and NOx climate cost functions based on local weather
No full textAviation contributes significantly to anthropogenic global warming, and one promising possibility for mitigation is climate-optimised routing. For the REACT4C project a novel approach was used to simulate the variation of aviation water vapour and NOx emission climate impact with location and weather patterns, but this is too computationally expensive to apply beyond initial research. Results showed about 10% climate impact reduction from a 1% cost increase. For implementation of climate-optimised routing, algorithms are needed which will allow climate impact to be estimated in real-time from weather predictions. This research focuses on formulating algorithmic approximations of aviation water vapour and NOx emission climate impact based on local weather data by systematically examining correlations between climate impact data and weather data at the time of emission in the REACT4C dataset. The methods and models used for generating the REACT4C data are assessed in detail down to their first publications and potential errors and omissions are identified. The analysis is split into direct water vapour, short-lived ozone from NOx, and methane from NOx climate impact. Long-lived ozone and stratospheric water vapour from methane effects are neglected. The water vapour and NOx ozone and methane Climate Cost Function (CCF) results from REACT4C are reverse-engineered to the original grid they were emitted from to prevent inflation of statistical power. Weather and chemistry data at the time of emission are interpolated to the same grid for regression analysis. Literature reviews are used to identify causal predictors and derived variables. A variety of statistical tools are applied to assess variability of the CCFs and search for the best predictors. Four algorithms are developed for each species, using zero-dimensional instantaneous regression analysis. A tailored trade-off framework is applied to choose the best algorithm for application. The chosen algorithmic CCF for water vapour emissions is linear with potential vorticity and has an adjusted R2 of 0.59. Both the mean and the variance of the water vapour climate impact appear strongly determined by the altitude of an emission relative to the tropopause. The relationship between water vapour CCF results and emission altitude is investigated to critically reflect and expand on results from a previous publication. The chosen algorithmic CCF for ozone is bilinear with geopotential and temperature plus their interaction and has an adjusted R2 of 0.42. Ozone climate impact appears moderately determined by altitude and temperature of the emission location. The relationship between ozone CCF results, background NOx concentration and latitude during emission is investigated to critically reflect and expand on results from a previous publication. The chosen algorithmic CCF for methane is bilinear with geopotential and the solar incidence, and has an adjusted R2 of 0.17. Methane climate impact has low variability and is relatively independent of weather at the time and location of emission. The relationship between methane CCF results and background NOx concentrations during emission is investigated to critically reflect and expand on results from a previous publication. Methane climate impact can be more accurately predicted by using simulated ozone climate impact, but the variance left unexplained by the ozone algorithm would lead to worse results in application. The correlation between methane and ozone is weaker than in previous studies. Chemical concentrations, lightning frequency, and lightning NOx production at the time and location of emission do not predict aviation NOx climate impact beyond the extent of basic meteorology unless a large amount of predictors are included in the regression. The chain of models and assumptions from basic climate science to algorithmic CCFs is assessed to identify relative effects on uncertainty of the results. Several steps are identified that should be revisited and several opportunities for future data analyses to increase understanding and certainty of algorithmic CCFs. Future steps for research into and application of algorithmic CCFs depend on upcoming verification activities for the results presented here.Aerospace EngineeringControl & Operations / Aircraft Noise and Climate Effects (ANCE)Aerospace Engineerin
Climate Impact of a Potential Supersonic Fleet
No full textWithin the EU-project SCENIC the impact of a potential
supersonic fleet has been investigated. The methodology
how to estimate its climate impact is presented. A number
of sensitivity studies are analysed to identify options to
minimise climate impact. Since stratospheric water vapour
emissions are the most important contributor to climate
change induced by supersonics those scenarios are
minimising the climate impact which have the lowest cruise
altitude.
In order to include climate aspects in multi-disciplinary
optimisation for supersonics an assessment tool (AirClim)
has been developed within the EU Integrated Project
HISAC, which is briefly presented. The main atmospheric
input data describe the atmosphere’s sensitivity to the
emission region. Based hereon a functional relationship
has been developed between basic (supersonic) aircraft
design parameters (cruise altitude, fuel consumption) and
climate change
Assessing the appropriateness of different climate modelling approaches for the estimation of aviation NOx climate effects
No full textAviation’s contribution to anthropogenic global warming is estimated to be between 3 – 5% [1]. This assessment comprises two contributions: the well understood atmospheric impact of carbon dioxide (CO2) and the more uncertain non-CO2 effects. The latter pertain to persistent contrails and pollutants like nitrogen oxides (NOx), water vapor (H2O), sulfur oxides (SOx) and soot particles. NOx emissions are involved in non-linear processes that result in the short-term production of ozone (O3) and longer-term destruction of methane (CH4), stratospheric water vapor (SWV), and primary mode ozone (PMO). The aviation-attributable impacts arising from this short-term increase in O3 can vary by more than a factor of 1.5 depending on the selected modelling approach. This O3 increase is associated with the second largest warming effect across aviation’s main climate forcers [1]. We therefore quantify this figure using three modelling approaches (an Eulerian and a Lagrangian tagging scheme as well as a perturbation approach) at three potential aircraft cruise altitudes (200, 250 and 300 hPa) at which NOx pulse emissions are introduced in the Americas, Africa, Eurasia and Australasia. In general, the tagging method computes the contribution by an emission source to the concentration of a chemical species while a perturbation approach consists in calculating the total impact of an emission to the concentration of a species by means of subtracting two simulations: one with all emissions and a second without the specific source’s emissions. We compare results from Eulerian and Lagrangian simulations using the same climate-chemistry code: the ECHAM5/MESSy Atmospheric Chemistry (EMAC) model. With the Eulerian setup, we are able to capture non-linear processes and feedback effects, but not track the transport of emitted species in detail. The Lagrangian setup [2], on the other hand, allows for the accompaniment of thousands of air parcel trajectories, but at the cost of assuming a simplified linear chemistry mechanism. We find that the Lagrangian tagging approach provides the largest estimates for O3 production and radiative forcing (RF), followed by the Eulerian tagging scheme and lastly by the perturbation method. We therefore investigate the appropriateness of each of these in quantifying aviation’s total and marginal climate effects by addressing the following research questions: 1) By how much are the estimates for the short-term NOx-induced O3 perturbation and consequent RF varying across the three modelling approaches and why? 2) How does this RF vary with emission altitude within the upper Troposphere/lower Stratosphere (UTLS)?[1] Lee, D.S., Fahey, D.W., Skowron, A., Allen, M.R., Burkhardt, U., Chen, Q., Doherty, S.J., Freeman, S., Forster, P.M., Fuglestvedt, J., Gettelman, A., De León, R.R., Lim, L.L., Lund, M.T., Millar, R.J., Owen, B., Penner, J.E., Pitari, G., Prather, M.J., Sausen, R., and Wilcox, L.J.: The contribution of global aviation to anthropogenic climate forcing for 2000 to 2018, Atmos. Environ., 244, 117834, https://doi.org/10.1016/j.atmosenv.2020.117834, 2021.[2] Maruhashi, J., Grewe, V., Frömming, C., Jöckel, P., and Dedoussi, I. C.: Transport patterns of global aviation NOx and their short-term O3 radiative forcing – a machine learning approach, Atmos. Chem. Phys., 22, 14253–14282, https://doi.org/10.5194/acp-22-14253-2022, 2022
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