Der Vortrag beschreibt 

1) die aktuellen Probleme bei der Vorhersage persistenter Kondensstreifen zum Zwecke der umweltgerechten Flugplanung

2) Wo diese Probleme herrühren

3) Wie diese Probleme zu lösen sin

Gierens, Klaus Martin

Peter, Patrick

Wilhelm, Lena

Institute of Transport Research:Publications

Forecasting conditions for contrail developmentKlaus Gierens, DLR Oberpfaffenhofenwith contributions from L. Wilhelm, P. Peter, et al.DLR.de •  Slide 1 •  Klaus Gierens et al.  •  GbD Non-CO2 conference 20.09.2022This work has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreements No 875036 and 101056885Forecasting persistent contrails – a challenging problemSchmidt-Appleman criterion (RHmax>1) Contrail persistence criterion (RHi>1)DLR.de •  Slide 2 •  Klaus Gierens et al.  •  GbD Non-CO2 conference 20.09.2022DLR.de  •  Folie 3Forecasting persistent contrails – a challenging problemRed: No contrails or at least no persistence possible (acc. to MOZAIC data)Black: Persistent contrails possible (acc. to MOZAIC data)Blue: Persistent contrails with strong instantaneous RF possible (acc. to MOZAIC data)Many quite dry cases in ERA-5 where MOZAIC measurements show ice supersaturation and SAC fulfilled DLR.de •  Slide 3 •  Klaus Gierens et al.  •  GbD Non-CO2 conference 20.09.2022Thermodynamic conditions (temperature and humidity)Red: No contrails or at least no persistence possible (acc. to MOZAIC data)Black: Persistent contrails possible (acc. to MOZAIC data)Blue: Persistent contrails with strong instantaneous RF possible (acc. to MOZAIC data)SAC TmaxSACDLR.de •  Slide 4 •  Klaus Gierens et al.  •  GbD Non-CO2 conference 20.09.2022What makes prediction of ice supersaturation so difficult?Strong variability of water vapourWater vapour participates in dynamic, thermodynamic, chemical and aerosol processes on a multitude of spatial and time scales.This causes strong variability and sharp gradients in the water vapour field of the upper troposphere.Extremal, non-equilibrium states like ice-supersaturation are much more sensitive to changing conditions than are „normal“ states.DLR.de •  Slide 5 •  Klaus Gierens et al.  •  GbD Non-CO2 conference 20.09.2022Other constituents and variables have smooth fieldsIn contrast, gaseous emissions (CO2, NOx) participate only in chemical processes; their aCCFs are smooth and follow roughly the large-scale circulation patterns.Temperature fields as well are much smoother than the water vapour field. Figures from Rao et al., 2021, and P. PeterContrail aCCF at a certain timeDLR.de •  Slide 6 •  Klaus Gierens et al.  •  GbD Non-CO2 conference 20.09.2022Lagrangian simulations of spatially close contrailsECHAM5-ATTILA L41 Water vapor pulse emissions are released on the start point of 50 trajectories and life cycle of contrails is investigated Note the different possibilities:Some-times the 50 contrails behave similarly, but sometimes there is a wide diversity in position and propertiesP. Peter, phd-workDLR.de •  Slide 7 •  Klaus Gierens et al.  •  GbD Non-CO2 conference 20.09.2022Huge variability in instantaneous (individual) radiative forcingFigures from Wilhelm et al. 2021 exponential distributionfirst order effect curveDLR.de •  Slide 8 •  Klaus Gierens et al.  •  GbD Non-CO2 conference 20.09.2022How can the forecast of persistent contrails be improved?We need much more regularly-obtained humidity data for the upper troposphere (flight levels)• Only few aircraft equipped with WV sensors in the framework of the AMDAR system• Main purpose is to provide vertical soundings during ascent and descent, no measurement during cruise• Needs new technical developments• Should be free of costs for weather offices (win-win situation)https://flyht.com/weather-sensors/wvss-ii/DLR.de •  Slide 9 •  Klaus Gierens et al.  •  GbD Non-CO2 conference 20.09.2022Cruise level RH data assimilation and improved cirrus representation BeCoM project work packageData assimilation of cruise level humidity data (various sources)Improved cirrus physics that better represents the interaction between cirrus clouds and their parent ice supersaturated regionsValidation and uncertainty analysisProject just started, will run until May 2026DLR.de •  Slide 10 •  Klaus Gierens et al.  •  GbD Non-CO2 conference 20.09.2022Dynamical proxiesThe dynamical fields• Relative vorticity• Potential vorticity• Normalized geopotential• Lapse ratehave distinctly differing conditional probability distributions.Combining their values can inform contrail   persistence prediction.DLR.de •  Slide 11 •  Klaus Gierens et al.  •  GbD Non-CO2 conference 20.09.2022Summary and future workPART 1:• Although weather models simulate quite reasonable thermodynamic fields, forecasting contrail persistence on the spot is currently not reliable. It works better for regional and time-period based predictions.PART 2:• WV is involved in many processes and thus much more variable than other chemical compounds or the temperature field, for instance. While CCFs of other emissions are smooth, those for contrails are patchy.• Sometimes, contrail formed close to each other display wide variety of evolution (butterfly effect)• Background conditions (weather, radiation) induce a huge variability of individual forcing values. PART 3:• Regular measurements in sufficient quantities of relative humidty at cruise levels are urgently needed.• These need to be assimilated into NWP models. Cirrus representations in NWP models need improvements.• Dynamical proxies can be used in modern statistical methods to provide probabilistic contrail forecasts.DLR.de •  Slide 12 •  Klaus Gierens et al.  •  GbD Non-CO2 conference 20.09.2022

Forecasting conditions for contrail development

https://elib.dlr.de/188455/1/Gierens_Contrail_prediction.pdf

Forecasting conditions for contrail development

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