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MICHAEL MAHONEY: The MTP is a passive microwave radiometer,
so it doesn't emit any radiation like a radar does.
It only receives radiation emitted by
mostly oxygen molecules in the Earth's atmosphere.
Oxygen molecules are homogeneously mixed
in the atmosphere and depending upon
the amount of radiation that we get from them,
we can tell the temperature of the atmosphere.
For this campaign,
one of the most important measurements we can make
is the temperature of the coldest point in the atmosphere.
Now, this instrument doesn't just measure
the temperature "in situ" or at the aircraft's level,
it actually measures a temperature profile
through the atmosphere.
And generally speaking, on this campaign,
the temperatures will be colder above the airplane
but we need to know how cold
and we need to know that for two reasons.
One is that the fuel on the jet can actually turn to
jelly if it gets too cold.
So we want to avoid going into air that is too cold.
On the scientific side,
what's really important is to know the cold point,
because the coldest temperature in the atmosphere
acts like a throttle
which controls the transport of water vapor,
which is a powerful greenhouse gas into the stratosphere.
And so we want to know what that cold point temperature is
and where it is, so that we can tell
how much water vapor is getting into the stratosphere
and affecting climate change and global warming.
RICHARD DENNING: The Microwave Temperature Profiler
is composed of two parts.
There is an external,
or nearly external part, called the center unit
that has a microwave antenna
that rotates vertically in the atmosphere
and it takes samples at 10 different positions
in the atmosphere at different elevation angles.
At each stop in the elevation angle
it looks out at different distance, three different distances
so that it can make measurements
of about 20 different parameters
that tell us what the temperature is above
and below the airplane at different altitudes.
Inside the pressurized part of the aircraft,
there are two boxes that control the MTP.
The lower box, the larger box is the actual control sequencer
for the instrument.
It records all of the data on a hard drive.
And then there is also a communications computer
that provides the communications to the ground over the network
so that we can see the data in real time.
The data arrives on the ground,
The software processes it into an actual image,
a graph, of the temperature profile
while the plane is flying.
And so actual flight decisions can be made
based on what the temperature looks like around the airplane.
MICHAEL MAHONEY: The MTP is, first off, a meteorological measurement
and it gives you the vertical state of the atmosphere ,
temperature and pressure.
and that is very important for interpreting other measurements,
For example, scientists want to know
where the tropopause height is,
the transition from the coldest temperatures at the tropospause
to warmer temperatures in the stratosphere.
And the only way you can do that is with a microwave temperature profiler.
And so scientists want to know whether they're
in the stratosphere or whether they're in the troposphere,
because that helps them interpret
trace gas measurements,
because most of the measurements are "in situ" measurements
and you want to know whether you are in the stratosphere or
in the troposphere in order to make sense to them.
So that is the most important contribution.
But it turns out that we can use our measurements
also to study wave activity, or atmospheric dynamics.
And in the case of this campaign,
that is important because gravity waves,
oscillations in the height of air parcels in the stratosphere,
If you go to the Rocky Mountains
you will see these lenticular clouds
and those are gravity waves, OK?
And they affect the transport of gases
between the stratosphere and the troposphere
or the troposphere and the stratosphere.
That is called strat trope exchange.
And being able to study these atmospheric dynamics,
which you can only do with MTP,
is a very important contribution.
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