The Coin-Flip: Unbiased Scheduling in the OTREC GV Flights

On August 17, the day I came aboard the Gulfstream V (GV), the conditions along the coastline of Costa Rica in the Eastern Pacific were rather placid. From out the windows, we were met with views of trade cumulus clouds, stretches of open sea, and the occasional isolated shallow cumulus cloud. No signs of organized deep convection were in sight, except for those in the distance that our colleagues aboard the NOAA P-3 Hurricane Hunter were investigating. Why would a project focused on the nature of deep convection spend time to observe areas without convection? Well, to understand deep convection, we also must understand why it doesn’t happen.

Figure 1: An image taken from the GV flight over the Eastern Pacific on 8/17

When planning this project, the PIs decided that it would be vital to study a variety of conditions in the regions of concern. We couldn’t let our bias command the schedule to the point where the GV would solely chase deep convection. OTREC had to look at the full spectrum of conditions in order to understand what factors in the Eastern Pacific and Caribbean lead to conditions where we see little or no deep convection, widespread and organized deep convection, and everything in between

For this reason, the project developed an unbiased system to schedule the GV flights. The GV usually flies lawnmower patterns within two boxes of interest, one (B2) in the Eastern Pacific off the coastline of Costa Rica, and another (B1) which spans in two regions, one in the Caribbean (B1b) and one off the eastern coast of Colombia (B1a) (see the picture below).

B2

B1a

B1b

Figure 2: The GV flight operation boxes

In the flight schedule, the GV flies within the B1 box first, and the next day, it flies within the B2 box. After the B1 flight, the fate of this two-day flight schedule is left up to the epitome of fairness… a coin flip. The coin flip determines how many days we take in between the last B2 flight and the next B1 flight. The PIs, Dave and Zeljka, take a coin and flip it four times. Each head represents one day. Once the number of heads they flip is counted, we add one extra day. This give us the possibilities of having one to five days between the B2 and B1 flights. For the sake of GV maintenance and the restricted schedule, breaks of one and five days can only occur once.

After our latest B2 flight on 8/17, the pilots got to take a turn in flipping the coin to determine when the GV would take to the air next. To their dismay, they got four heads! Four plus one leaves us five days before we hit the skies again. However, since we’ve already taken a five-day pause, the plan is to take a four-day break; we’ll be back with more data from our B1 region this Thursday!