The ARM Mobile Facility site, deployed at Truro, Massachusetts, is shown here in an earlier and warmer time of the year.We are back on Cape Cod for the second TCAP intensive operations period, which we abbreviate as IOP. The weather conditions have been challenging (more on that later), but we have managed to get in a number of good research flights between the storms. We made one important change to the G-1 aircraft for the second IOP, and that was to include a special inlet called a Counterflow Virtual Impactor, or CVI. The CVI uses a stream of air exiting from the inlet to keep small particles outside. This jet is called a counterflow because it is going in the opposite direction of the sample flow. Cloud drops, which are much larger than other atmospheric particles, have enough momentum to move through the counterflow, but smaller particles do not. The CVI allows us to look at the size distribution and chemical composition of the particles that act as seeds for the cloud drops (these particles are also known as cloud condensation nuclei or CCN).
Now more about the weather. We bore the full brunt of winter storm Nemo at the airport and ground site near Truro, Massachusetts. Power was out at both locations and has only recently been restored at the ARM Mobile Facility ground site. The research aircraft was kept in the hangar for a couple of days, while the airport snowplows worked to clear the runways, taxi ways, and ramps. The lowest surface pressure measured at the ground site was about 980 mb, and the peak sustained winds were about 25 m/s (56 mph). Normal surface pressure at sea level is generally a bit higher then 1000 mb. No wonder there were weather issues!
