Wyoming King Air

Unfortunately we did not get to fly today. However, we will almost certainly fly tomorrow. We have not yet gotten permission from ATC to fly below 7,000 ft on IFR (Instrument Flight Rules) and the clouds were too shallow such that flying at 7,000 ft, we would not have been able to measure any clouds. The height of the trade wind inversion was very low today, but it will be much much higher tomorrow. A cold front is going to come through tonight, extending the cloud layer up to 700 hPa or higher. Even if we do not get permission by tomorrow, we will be able to measure clouds at 7,000 ft so it is quite likely that we will fly. While we didn't fly, we did get to visit the aircraft and learn about how the cloud physics instruments work. I'll give you a little overview of some of the instruments below.

This is the Wyoming King Air; it is owned and operated by the University of Wyoming.  It seats four staff members inside, two of which will be occupied by the DOMEX crew each flight.  It is completely decked out with instruments inside and out.

Right Wing Instruments.

Left Wing Instruments.

I'll go through some of them in greater detail...

This is the PCASP instrument which measures aerosol particles.  It takes air (and aerosol particles) in, dries it, and measures the size of particles with an optical particle counter.  It can make measurements 10 times a second!

This instrument measures the liquid water content.  The little wire you see there is kept at a constant ~120C but when water lands on the instrument and then evaporates, it decreases the temperature of the probe.  Power must be supplied to keep the temperature constant and from the amount of power, they can back out the amount of liquid water in the air.

This is the Reverse Flow Temperature probe.  The tubes out the sides are angled such that they create low pressure inside the instrument and air flows around from the back.  By having air flow around, it reduces the amount of water that gets into the instrument.

This is the CIP optical array probe.  A laser is pointed from one side to the other and is focused on an array of diodes.  As particles pass through the probe, they make a shadow on the array.  The laser strobes at a high rate and in this way a picture of the cloud droplets is formed and particle size is measured.

 This is the gust probe.  It sticks out in front of the aircraft and measures winds and turbulence.  There are small inlets on the probe that measure the total impact pressure and the pressure differential on different sides of the probe.  By comparing these to the static pressure, the angle of attack, the ground speed, and many other needed corrections, the wind speed and direction of airflow in the atmosphere can be determined.

 This is the Gerber probe and it measures variables having to do with cloud droplets.  As air passes through the probe, an IR laser measures the amount of forward scattering.  The volume, surface area, and size of cloud droplets is measured. 

This is the CDP probe which also measures cloud particles.  It works in a similar way to some of the other instruments already mentioned; a diode laser is paired with sensing optics and the forward scattering of the laser off of cloud particles is measured.  It also gives cloud droplet spectra information.

I'm sure I've already bored you with all the instrument descriptions so I'll stop there for now.  Two others that don't bode well to pictures are the Wyoming Cloud Radar and the Cloud Lidar.  One person could spend their entire lifetime on a data set as big as the one we're about to be getting...1 flight down, 19 more to go!