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| Titel |
A methodology for in-situ and remote sensing of microphysical and radiative properties of contrails as they evolve into cirrus |
| VerfasserIn |
H. M. Jones, J. Haywood, F. Marenco, D. O'Sullivan, J. Meyer, R. Thorpe, M. W. Gallagher, M. Krämer, K. N. Bower, G. Rädel, A. Rap, A. Woolley, P. Forster, H. Coe |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 12, no. 17 ; Nr. 12, no. 17 (2012-09-11), S.8157-8175 |
| Datensatznummer |
250011439
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| Publikation (Nr.) |
 copernicus.org/acp-12-8157-2012.pdf |
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| Zusammenfassung |
Contrails and especially their evolution into cirrus-like clouds are thought
to have very important effects on local and global radiation budgets, though
are generally not well represented in global climate models. Lack of
contrail parameterisations is due to the limited availability of in situ
contrail measurements which are difficult to obtain. Here we present a
methodology for successful sampling and interpretation of contrail
microphysical and radiative data using both in situ and remote sensing
instrumentation on board the FAAM BAe146 UK research aircraft as part of the
COntrails Spreading Into Cirrus (COSIC) study.
Forecast models were utilised to determine flight regions suitable for
contrail formation and sampling; regions that were both free of cloud but
showed a high probability of occurrence of air mass being supersaturated
with respect to ice. The FAAM research aircraft, fitted with cloud
microphysics probes and remote sensing instruments, formed a distinctive
spiral-shaped contrail in the predicted area by flying in an orbit over the
same ground position as the wind advected the contrails to the east. Parts
of these contrails were sampled during the completion of four orbits, with
sampled contrail regions being between 7 and 30 min old. Lidar
measurements were useful for in-flight determination of the location and
spatial extent of the contrails, and also to report extinction values that
agreed well with those calculated from the microphysical data. A shortwave
spectrometer was also able to detect the contrails, though the signal was
weak due to the dispersion and evaporation of the contrails. Post-flight the
UK Met Office NAME III dispersion model was successfully used as a tool for
modelling the dispersion of the persistent contrail; determining its
location and age, and determining when there was interference from other
measured aircraft contrails or when cirrus encroached on the area later in
the flight.
The persistent contrails were found to consist of small (~10 μm)
plate-like crystals where growth of ice crystals to larger sizes
(~100 μm) was typically detected when higher water
vapour levels were present. Using the cloud microphysics data, extinction
co-efficient values were calculated and found to be 0.01–1 km−1. The
contrails formed during the flight (referred to as B587) were found to have
a visible lifetime of ~40 min, and limited water vapour
supply was thought to have suppressed ice crystal growth. |
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