The atmospheric impact of aircraft NOx emissions are studied using updated aircraft inventories for the year 2006, in order to estimate the photochemistry-related mitigation potential of shifting ...cruise altitudes higher or lower by 2000 ft. Applying three chemistry-transport models (CTM) and two climate-chemistry models (CCM) in CTM mode, all including detailed tropospheric and stratospheric chemistry, we estimate the short-lived radiative forcing (RF) from O3 to range between 16.4 and 23.5 mW m−2, with a mean value of 19.5 mW m−2. Including the long-lived RF caused by changes in CH4, the total NOx-related RF is estimated to about 5 mW m−2, ranging 1–8 mW m−2. Cruising at 2000 ft higher altitude increases the total RF due to aircraft NOx emissions by 2 ± 1 mW m−2, while cruising at 2000 ft lower altitude reduces RF by 2 ± 1 mW m−2. This change is mainly controlled by short-lived O3 and show that chemical NOx impact of contrail avoiding measures is likely small.
Display omitted
•Multi-model study on the aircraft NOx-related effect on the atmosphere.•New inventory for aircraft NOx emissions, representative for year 2006.•The total RF due to NOx emissions is found to be about 5 mW m2.•Shifting cruise altitudes up or down by 2000 ft changes RF by about 2 mW m2.•Contrail-avoiding measures will likely give small NOx impact.
Variability in the strength of the stratospheric Lagrangian mean meridional or Brewer‐Dobson circulation and horizontal mixing into the tropics over the past three decades are examined using ...observations of stratospheric mean age of air and ozone. We use a simple representation of the stratosphere, the tropical leaky pipe (TLP) model, guided by mean meridional circulation and horizontal mixing changes in several reanalyses data sets and chemistry climate model (CCM) simulations, to help elucidate reasons for the observed changes in stratospheric mean age and ozone. We find that the TLP model is able to accurately simulate multiyear variability in ozone following recent major volcanic eruptions and the early 2000s sea surface temperature changes, as well as the lasting impact on mean age of relatively short‐term circulation perturbations. We also find that the best quantitative agreement with the observed mean age and ozone trends over the past three decades is found assuming a small strengthening of the mean circulation in the lower stratosphere, a moderate weakening of the mean circulation in the middle and upper stratosphere, and a moderate increase in the horizontal mixing into the tropics. The mean age trends are strongly sensitive to trends in the horizontal mixing into the tropics, and the uncertainty in the mixing trends causes uncertainty in the mean circulation trends. Comparisons of the mean circulation and mixing changes suggested by the measurements with those from a recent suite of CCM runs reveal significant differences that may have important implications on the accurate simulation of future stratospheric climate.
The IPCC Special Report on Aviation and the Global Atmosphere (PENNER et al., 1999) highlighted the variability between model calculations of both the impact of sub- and supersonic aircraft. This ...study provides valuable information on the transport of aircraft-like emissions from sub- and supersonic cruise altitudes and latitudes. The accurate reproduction of the transport of aircraft emissions from their source region is extremely important in any study of the atmosphere. The results of this tracer study have revealed that the transport of aircraft-like tracers is highly variable between models during a single two year integration. If aircraft emissions are considered to remain inactive in the atmosphere then model calculations predict that it is possible, within the course of only two years, to transport subsonic aircraft emissions from the midlatitude upper troposphere into the polar lower and middle stratosphere. This result emphasises the importance of reproducing the correct transport processes throughout the lower atmosphere in calculations of the atmospheric impact of aircraft. Der ,,IPCC Special Report on Aviation and the Global Atmosphere (PENNER et al., 1999)'' betonte die große Streuung der Modellergebnisse bezüglich des Einflusses von Unter- und Überschallluftverkehr. Die vorliegende Studie bietet nützliche Informationen zum Transport von Spurenstoffen, die Emissionsmuster aufweisen, welche vergleichbar sind mit Emissionen aus dem Unter- und Überschallreiseflug. Die genaue Wiedergabe des Transportes von Spurenstoffen des Luftverkehrs ist von besonderer Bedeutung für jede Untersuchung bezüglich des Luftverkehrseinflusses. Die Ergebnisse dieser Studie zeigen, dass der Transport von luftverkehrsähnlichen Spurenstoffen eine große Streuung unter den Modellen aufweist, bezogen auf eine zweijährige Simulation Unter der Annahme, dass Luftverkehrsemissionen passiv in der Atmosphäre transportiert werden, zeigen Modellrechungen, dass Spurenstoffe, die in mittleren Breiten in der oberen Troposphäre emittiert werden, innerhalb von zwei Jahren in die polare untere und mittlere Stratosphäre transportiert werden können. Die Ergebnisse zeigen deutlich die Notwendigkeit einer korrekten Modellierung von Transportprozessen der unteren Atmosphäre für die Untersuchung des Einflusses des Unter- und Überschallflugverkehrs auf die Atmosphäre.
The atmospheric impact of aircraft NO x emissions are studied using updated aircraft inventories for the year 2006, in order to estimate the photochemistry-related mitigation potential of shifting ...cruise altitudes higher or lower by 2000 ft. Applying three chemistry-transport models (CTM) and two climate-chemistry models (CCM) in CTM mode, all including detailed tropospheric and stratospheric chemistry, we estimate the short-lived radiative forcing (RF) from O3 to range between 16.4 and 23.5 mW m-2, with a mean value of 19.5 mW m-2. Including the long-lived RF caused by changes in CH4, the total NO x -related RF is estimated to about 5 mW m-2, ranging 1-8 mW m-2. Cruising at 2000 ft higher altitude increases the total RF due to aircraft NO x emissions by 2 plus or minus 1 mW m-2, while cruising at 2000 ft lower altitude reduces RF by 2 plus or minus 1 mW m-2. This change is mainly controlled by short-lived O3 and show that chemical NO x impact of contrail avoiding measures is likely small.
A critical problem in studying ribosome-inactivating proteins (RIPs) lies in the very limited possibility to produce them in heterologous systems. In fact, their inherent toxicity for the producing ...organism nearly always prevents their recombinant expression. In this study, we designed, expressed and characterized an engineered form of the RIP saporin (SapVSAV), bearing a C-terminal extra sequence that is recognized and bound by the second PDZ domain from murine PTP-BL protein (PDZ2). The co-expression of SapVSAV and PDZ2 in Escherichia coli BL21 cells greatly enhances the production of the toxin in a soluble form. The increase of production was surprisingly not due to protection from bacterial intoxication, but may arise from a stabilization effect of PDZ2 on the toxin molecule during biosynthesis. We found that once purified, SapVSAV is stable but is not toxic to free ribosomes, while it is fully active against human cancer cells. This strategy of co-expression of a toxin moiety and a soluble PDZ domain may represent a new system to increase the production of recombinant toxic proteins and could allow the selection of new extra sequences to target PDZ domains inside specific mammalian cellular domains.
PDF
