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There
are new observational requirements attached to each of these
topics. There are also new observational facilities that become
available, such as airborne Doppler radars that can give access
to the internal structure of cloud systems. For these reasons,
one of the first significant step of the FASTEX project has been
to set-up and run a major two months field project (Fig. B,
previous page). Its specific objectives were to document the
life-cycle of North-Atlantic cyclones, in order to deliver the
data needed to address the topics listed above.
The project and its basic plans emerged
from French and British groups in 1993. They attracted scientists
from the United States of America, Canada, Ireland and a number
of other countries and organizations, including the European
Commission and the World Meteorological Organization. This was
needed by the scale of the observational challenge: tracking
about 10 cyclones from their birth in the western or middle ocean
to their mature stage close to the European coasts (Fig. D).
The field phase of FASTEX thus took place
in January and February 1997. Beside a significant overhaul of
the operational observing network, up to 4 ships (see what it
was on board on the animation)
had been positioned in the middle of the Atlantic, up to 7 instrumented
aircraft were available on air fields on both sides of the ocean.
This observing system was coordinated by a special Operations
Centre located at Shannon, Ireland.
The observing period has reached the following
goals:
- about ten mature and developing cloud
systems and related cylones have been sampled by airborne Doppler
radars (Fig. E) and dropsondes
(Fig. I); for about half these cases,
the structure of the system has been observed on scales unheard
of so far with in-situ data; this was the data required to make
some progress on the internal organization of large stratiform
cloud systems;
- about ten cyclones have been observed
at several key stages of their life-cycle with radiosondes and
dropsondes, thus enabling the documentation of life-cycles, which
is central in modern cyclone theory and impacts all other topics;
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