Contrail Lifetime in Context of Used Flight Levels

Abstract

The impact of contrails on Earth’s climate is probably not negligible, yet there are only a few initiatives aimed at mitigating the influence of aviation on the environment. To achieve zero CO2 emissions, aircraft manufacturers and airlines propose complex and costly methods and technologies such as synthetic fuels, hybrid engines, or expensive carbon offsetting. On the other hand, contrail mitigation by achievable operational measures has the potential to achieve benefits with a very positive cost-benefit ratio without the need for a complex technological change in aviation. It seems that one suitable tool for contrail mitigation is the change in flight level. Therefore, we focused on the assessment of flight levels with typical contrails occurrence and common flight levels used by air traffic management. Some influence of tropopause height throughout the year was presumed to be a factor, therefore we studied different times of the year. The tropopause height influences not only contrail occurrence but also the preferred flight level, as airlines tend to avoid flying directly in the tropopause. We present some basic statistics about the frequency of contrail occurrence based on flight level. We focused on long-lived contrails to emphasize the more important contrails in this context. Information about flight levels is based on ADS-B data transmitted by aircraft and recorded by a ground station near the place of contrail occurrence, which was based on optical survey.

Validation of a Contrail Life-Cycle Model in Central Europe

“…A total of 82% of the contrails existed for less than one minute. For 26% of all contrails, we observed a lifetime longer than one minute [21].…”

“…In this case, the range of lifetimes would be interesting. Now that the contrail life-cycle model has been validated, the contrail optical properties model [79] will be linked to the camera observations and aircraft pairings [21] in the future. With the help of machine learning, correlations between location, altitude, aircraft type, atmospheric properties, and the radiative forcing of the contrails can be determined.…”

“…For this study, we only analyzed contrails whose complete diffusion took place within the camera field of view. The procedure is described in detail in [21].…”

“…The following steps include decoding and saving selected data to obtain only flight data relevant to our research such as altitude, speed, and heading. The International Civil Aviation Organization (ICAO) hexadecimal aircraft address serves as a unique identifier according to which all filtered and decoded data are assigned to individual aircraft records [21].…”

Carbon-Free Fuels Can Increase Aviation-Induced Cloudiness

“…The thermodynamic analysis presented herein is an essential prerequisite for future high-fidelity CFD simulations, as it identifies the contrail-forming conditions for which one needs to conduct CFD simulations. Identifying contrail-forming regions would also allow aircraft to avoid them by adopting alternative flight trajectories 12 or elevations 13 with minimal increased fuel consumption to mitigate contrail effects. Such strategic flight route and altitude planning can prove remarkably efficient, supported by data 14 that indicates close to 12% of flights within the North Atlantic-recognized as one of the globe's busiest air traffic routes-contribute to 80% of the annual contrail energy forcing in this specific area.…”