Identification

Title

Microphysics of aerodynamic contrail formation processes

Abstract

Aerodynamic condensation is a result of intense adiabatic cooling in the airflow over aircraft wings and behind propeller blades. Out of cloud, condensation appears as a burstlike fog (jet aircraft during takeoff and landing, propellers) or as an iridescent trail visible from the ground behind the trailing edge of the wing (jet aircraft in subsonic cruise flight) consisting of a monodisperse population of ice particles that grow to sizes comparable to the wavelength of light in ambient humidities above ice saturation. In this paper, the authors focus on aerodynamic contrail ice particle formation processes over jet aircraft wings. A 2D compressible flow model is used to evaluate two likely processes considered for the initial ice particle formation: homogeneous droplet nucleation (HDN) followed by homogeneous ice nucleation (HIN) and condensational growth of ambient condensation nuclei followed by their homogenous freezing. The model shows that the more numerous HDN particles outcompete frozen solution droplets for water vapor in a 0.5-1-m layer directly above the wing surface and are the only ice particles that become visible. Experimentally verified temperature and relative humidity–dependent parameterizations of rates of homogeneous droplet nucleation, growth, and freezing indicate that visible aerodynamic contrails form between T = -20° and -50°C and RH ≥ 80%. By contrast, combustion contrails require temperatures below -38°C and ice-saturated conditions to persist. Therefore, aerodynamic and combustion contrails can be observed simultaneously.

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document

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http://n2t.net/ark:/85065/d76t0nvb

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eng

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geoscientificInformation

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publication

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2016-01-01T00:00:00Z

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publication

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2015-09-01T00:00:00Z

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Copyright 2015 American Meteorological Society (AMS). Permission to use figures, tables, and brief excerpts from this work in scientific and educational works is hereby granted provided that the source is acknowledged. Any use of material in this work that is determined to be "fair use" under Section 107 or that satisfies the conditions specified in Section 108 of the U.S. Copyright Law (17 USC, as revised by P.L. 94-553) does not require the Society's permission. Republication, systematic reproduction, posting in electronic form on servers, or other uses of this material, except as exempted by the above statements, requires written permission or license from the AMS. Additional details are provided in the AMS Copyright Policies, available from the AMS at 617-227-2425 or amspubs@ametsoc.org. Permission to place a copy of this work on this server has been provided by the AMS. The AMS does not guarantee that the copy provided here is an accurate copy of the published work.

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OpenSky Support

organisation name

UCAR/NCAR - Library

full postal address

PO Box 3000

Boulder

80307-3000

email address

opensky@ucar.edu

web address

http://opensky.ucar.edu/

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