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Contrail formation within cirrus: ICON-LEM simulations of the impact of cirrus cloud properties on contrail formation

Verma, Pooja and Burkhardt, Ulrike (2022) Contrail formation within cirrus: ICON-LEM simulations of the impact of cirrus cloud properties on contrail formation. Atmospheric Chemistry and Physics (ACP), 22 (13), pp. 8819-8842. Copernicus Publications. doi: 10.5194/acp-22-8819-2022. ISSN 1680-7316.

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Official URL: https://acp.copernicus.org/articles/22/8819/2022/


Contrail formation within natural cirrus introduces large perturbations in cirrus ice crystal number concentrations, leading to modifications in cirrus microphysical and optical properties. The number of contrail ice crystals formed in an aircraft plume depends on the atmospheric state as well as aircraft and fuel properties. Our aim is to study contrail formation within cirrus and, in particular, the impact of pre-existing cirrus on the contrail formation processes. We implement a parameterization for contrail ice nucleation and the survival of contrail ice crystals within the vortex phase within the high-resolution ICON-LEM at a horizontal resolution of 625 m over Germany and modify the parameterizations in order to consider the impact of the pre-existing cirrus. We then simulate contrail formation and analyze the change in ice nucleation and survival due to the presence of cirrus ice crystals. We have selected two different synoptic situations to sample a large range of cirrus cloud properties from those representative of average thick in situ formed cirrus and liquid origin cirrus that are connected to a frontal system down to very thin cirrus within a high-pressure system. We find that contrail formation within cirrus mostly leads to increases in cirrus ice crystal numbers by a few orders of magnitude. Pre-existing cirrus has a discernible impact on the contrail formation threshold temperature and on contrail ice crystal number concentrations only if the cirrus ice water content is high and ice supersaturation is low. The cirrus ice crystals sucked into and subsequently sublimated within the aircraft's engine and the ice crystals mixed into the aircraft plume experiencing sublimation and later deposition lead to an increase in the contrail formation threshold temperature most of the time. Often this increase is negligible, but in the above atmospheric conditions the increase in the contrail formation threshold can be large, reaching maximum values of 2 K. Consequently, significant increases in ice nucleation are very seldom, but in areas of high cirrus ice water content and ice crystal number concentrations, contrail ice nucleation rates can be significantly increased, in particular at lower flight levels. Cirrus ice crystals can also lead to a reduction in ice nucleation, but negative changes are significantly smaller and less common. After nucleation cirrus and contrail ice crystals compete for water vapor, while the combined contrail and cirrus ice water mass grows. Once the aircraft plume gets trapped within the wake vortices and descends the plume relative humidity decreases so that eventually both cirrus and contrail ice crystals sublimate. We find that the impact of cirrus ice crystals on the contrail ice crystal loss within the descending vortices is negligible. Only for nucleation rates several orders of magnitude lower than the soot number emission index can the impact be noticeable, but the relevance of this impact is limited.

Item URL in elib:https://elib.dlr.de/190242/
Document Type:Article
Title:Contrail formation within cirrus: ICON-LEM simulations of the impact of cirrus cloud properties on contrail formation
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Burkhardt, UlrikeDLR, IPAhttps://orcid.org/0000-0002-0742-7176
Date:8 July 2022
Journal or Publication Title:Atmospheric Chemistry and Physics (ACP)
Refereed publication:Yes
Open Access:Yes
Gold Open Access:Yes
In ISI Web of Science:Yes
Page Range:pp. 8819-8842
Publisher:Copernicus Publications
Keywords:Contrails, cirrus cloud, contrail ice nucleation, contrail ice formation within cirrus
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:Air Transportation and Impact
DLR - Research area:Aeronautics
DLR - Program:L AI - Air Transportation and Impact
DLR - Research theme (Project):L - Climate, Weather and Environment
Location: Oberpfaffenhofen
Institutes and Institutions:Institute of Atmospheric Physics > Earth System Modelling
Deposited By: Verma, Pooja
Deposited On:17 Nov 2022 13:09
Last Modified:25 Nov 2022 12:38

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