Overnight Flights

One of the goals for the unmanned aerial vehicle (UAV) flights is to observe the atmosphere evolve over the course of a day. The lowest part of the Antarctic atmosphere is known for its frequent characteristic of the temperature being coldest near the surface and then increasing in temperature with height over the lowest few hundred feet. This characteristic is referred to as a temperature inversion because it is the inverse of the general condition of the temperature decreasing with increasing height (in the part of the atmosphere with all of the weather). The cooling at the surface is most pronounced during the nighttime hours when there is no heating from the sun. This means that one of the periods of day that we are interested in observing is during the overnight hours. This is when it is most expected to see such a temperature inversion and we are interested in how it changes during the nighttime hours. We completed UAV night flights this past Sunday evening through early Monday morning as well as the following overnight.

Flight path of the UAV in the early night sky. This was approximately a 12 second photograph.

The operation of the UAVs at night is not much different than during the day. The launching and landing of the UAV is the only tricky times during the flight. We do all of the pre-flight checkouts while remaining in the van. When it comes time to launch, John goes outside and I remain in the van to monitor the autopilot controls on the computer. Once the UAV is launched, it is actually easier to track the UAV at night because the lights on the UAV make it easier to identify in the nighttime sky. For the landing, it is key that John is able to make out the surface. With the light from the moon and white snow everywhere, it doesn't take much to see the surface clearly. If needed, I'll also turn on the headlights of the van to light up the surface for landing.

Time lapse photograph of the launch of the UAV at night. The lights are indicating different parts on the UAV.

Time lapse photograph of the flight of the UAV near the highest point of the profile. The UAV continues to fly in circles as it ascends and descends the flight path.

The flight path of the UAV as it is getting closer to the surface. Stargazers might be interested in noticing that that constellation in the center of the photo, just to the left of the UAV flight path, is the southern cross.

The temperatures in McMurdo were in the -30Fs when we went out to Pegasus Airfield Tuesday evening. That indicated that the temperatures were even colder at Pegasus. I placed my handheld thermometer out the window at one point during the drive and recorded an air temperature (not wind chill) of -56.7F. We stopped the van not long after that and I measured -54F. That sets a personal record for me that will be difficult to ever surpass.

Taking a moment to get outside and experience -54F air temperature. In my hand I am holding a small handheld weather station. The handheld weather station is reading -46F, which is about as cold as I could get in holding it still. Also, notice the snot-cicles on my nose (might need to zoom in to see).

We are into a routine with the UAV flights and we were able to complete 21 flights in five days. We are not anticipating to be flying over the next few days as some stormy weather is forecast to be moving through the area. In the future we will likely be doing flights from the early morning hours, before sunrise, through early afternoon to see the changes as the sun rises in the horizon.

A plot of temperatures from the vertical profiles made by the UAV on 11 September 2016. Notice the very cold temperatures near the surface and the dramatic increase in temperatures with increasing height right above the surface. This feature is referred to as a temperature inversion. It is also worthwhile noticing how the temperature profiles changed with approximately one hour and 45 minutes between each profile