[wind]
[rain] As the Hurricane and Severe
Storm Sentinel campaign takes off, the Global Hawk aircraft
will serve as a long-distance airborne laboratory designed to study the factors
that can create and drastically change tropical cyclones.
This airborne mission--
HS3 for short--is studying those storms, and one of the
targets of study is the Saharan Air Layer.
This warm, dusty mass of air originates from the Sahara and
drifts west into the Atlantic. The exact impact of the
Saharan Air Layer is unclear. Research has shown that the SAL
can weaken a storm by promoting downdrafts, and its
strong winds can increase vertical wind shear in and around the storm.
During the HS3 campaign, scientists will analyze the Saharan Air
Layer using a suite of instruments on board the unmanned Global Hawk
aircraft. One instrument, the Cloud Physics Lidar,
will gather data straight through storms and dusty air layers.
Braun: The Cloud Physics Lidar, or CPL, gives us the vertical profile
of the dust. So we can see not only where within the atmosphere it is, but
get a relative sense at least of how much dust there is
and the extent to which it's getting wrapped into the storm circulation.
The lidar works by sending 5,000 rapid light pulses a second
that bounce and scatter off any particles they encounter. The light
that bounces back to the instrument can help distinguish the type of particle,
which then gives us a better look at the anatomy of the storm.
Data from the Cloud Physics Lidar will not only improve models
of the Saharan Air Layer, but also expand the understanding of how
the dust interacts with the storms. Braun: That's really the measurement challenge
is to be able to collect the needed observations
of where the Saharan Air is, what its characteristics are, how
much does it penetrate into a storm, and when it does, what
is it actually doing to the storm? How is it inhibiting development? And those
are things that we're trying to answer.
[beeping, thunder]