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Susceptibility of contrail ice crystal numbers to aircraft soot particle emissions
Author(s) -
Kärcher B.,
Voigt C.
Publication year - 2017
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2017gl074949
Subject(s) - ice crystals , supersaturation , cirrus , sublimation (psychology) , soot , ice nucleus , atmospheric sciences , clear ice , environmental science , cloud condensation nuclei , ice cloud , particle number , aerosol , freezing point , nucleation , meteorology , cryosphere , chemistry , physics , radiative transfer , thermodynamics , sea ice , combustion , antarctic sea ice , psychology , organic chemistry , quantum mechanics , volume (thermodynamics) , psychotherapist
We develop an idealized, physically based model describing combined effects of ice nucleation and sublimation on ice crystal number during persistent contrail formation. Our study represents the first effort to predict ice numbers at the point where contrails transition into contrail cirrus—several minutes past formation—by connecting them to aircraft soot particle emissions and atmospheric supersaturation with respect to ice. Results averaged over an observed exponential distribution of ice supersaturation (mean value 15%) indicate that large reductions in soot particle numbers are needed to lower contrail ice crystal numbers significantly for soot emission indices around 10 15 (kg fuel) −1 , because reductions in nucleated ice number are partially compensated by sublimation losses. Variations in soot particle (−50%) and water vapor (+10%) emission indices at threefold lower soot emissions resulting from biofuel blending cause ice crystal numbers to change by −35% and <5%, respectively. The efficiency of reduction depends on ice supersaturation and the size distribution of nucleated ice crystals in jet exhaust plumes and on atmospheric ice supersaturation, making the latter another key factor in contrail mitigation. We expect our study to have important repercussions for planning airborne measurements targeting contrail formation, designing parameterization schemes for use in large‐scale models, reducing uncertainties in predicting contrail cirrus, and mitigating the climate impact of aviation.