Aviation and the Global Atmosphere

Aviation and the Global Atmosphere
ambient wind field (Freudenthaler
et al., 1995; Schumann et al.,
1995; Dürbeck and Gerz, 1996;
Gierens, 1996), and possibly
radiatively driven mixing (Jensen et
al., 1998d).
Contrails often become wide and
thick enough to induce radiative
disturbances that are sufficient to
be detectable in multispectral
satellite observations. They have
been observed at 1-km spatial
resolution with instruments such as
the Advanced Very High
Resolution Radiometer (AVHRR)
on board National Oceanic and
Atmospheric Administration
(NOAA) polar-orbiting satellites (e.
g., Lee, 1989) and at 4-km
resolution in the infrared with the
Geostationary Operational
Environmental Satellite (GOES)
(Minnis et al., 1998a). The AVHRR
channels in the 11- to 12-µm range
(4 and 5) are particularly suited to
detect thin ice clouds because of
the different emissivity of ice
particles in this spectral range
Figure 3-14: Correlation of mean annual contrail frequency and
estimated May 1990 aircraft fuel usage above 7-km altitude.
(King et al., 1992; Minnis et al., 1998c). Figure 3-12 shows, for example, a mid-European scene derived from AVHRR data in these channels, combined with the visible
channel to represent the surface, for a day when many line-shaped contrails were formed by heavy air traffic (Mannstein, 1997). The figure shows that aircraft trigger
contrail cirrus that evolves into cirrus clouds that are much more extensive in scale than the initial contrails. Such spread and deformed contrail cirrus can no longer be
distinguished from naturally occurring cirrus. In Figure 3-12, contrails that still have a line-shaped appearance cover about 5% of the scene.
Aged contrails often cannot be distinguished from cirrus, which poses an observational
problem in determining the frequency and area of coverage by contrails. An important
example of the persistence of contrails and their evolution into more extensive cirrus is
shown in Figure 3-13. An initial oval contrail observed in GOES-8 satellite images diffused
as it was advected over California until it no longer resembled its initial shape 3 h later
(Minnis et al., 1998a). The exhaust from this single aircraft flying for less than 1 h in a moist
atmosphere caused a cirrus cloud that eventually covered up to 4,000 km 2 and lasted for
more than 6 h. Other contrails and contrail clusters were observed to develop over periods
of 7 to 17 h, spreading to cover areas of 12,000 to 35,000 km 2 . Such dispersed contrails are
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