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Old 11-17-2009, 09:44 AM
Alferd Alferd is offline
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Join Date: Nov 2009
Posts: 22
Default another paper

Apparently, many times when you think the sky is clear, there really are cirrus clouds, so thin that you can’t see them from the ground. These are called “subvisual” clouds.

Here is an abstract to another scientific paper.
The entire paper can be found here:

Abstract. During the European heat wave summer 2003
with predominant high pressure conditions we performed a
detailed study of upper tropospheric humidity and ice particles
which yielded striking results concerning the occurrence
of ice supersaturated regions (ISSR), cirrus, and contrails.
Our study is based on lidar observations and meteorological
data obtained at Lindenberg/Germany (52.2_ N, 14.1_ E)
as well as the analysis of the European centre for medium
range weather forecast (ECMWF). Cirrus clouds were detected
in 55% of the lidar profiles and a large fraction of
them were subvisible (optical depth <0.03). Thin ice clouds
were particularly ubiquitous in high pressure systems. The
radiosonde data showed that the upper troposphere was very
often supersaturated with respect to ice. Relating the radiosonde
profiles to concurrent lidar observations reveals that
the ISSRs almost always contained ice particles. Persistent
contrails observed with a camera were frequently embedded
in these thin or subvisible cirrus clouds. The ECMWF cloud
parametrisation reproduces the observed cirrus clouds consistently
and a close correlation between the ice water path in
the model and the measured optical depth of cirrus is demonstrated.
Does that help your understanding of the issues at all?
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