Friday 20th September, afternoon.
After the thick cloud of the morning flight, and a satellite picture that showed cloud cover over the whole area we wanted to fly in, things were not looking too promising for this afternoon’s flight. This is because we want to fly low over the wetlands (at minimum safe altitude, which is about 500ft), however the pilots need to have sight of the ground in order to descend that low. With this in mind, we were slightly worried that we might not be able to get down to low level at all! But the only way to know what is out there is to go out and see, so we set off with our fingers crossed.
We were planning to head north out of Kiruna, but somewhere along the line some wires got crossed, and the pilots set a course to the way point to the south. The confusion unfolded thusly (I paraphrase):
Ian (pilot): heading for way point N7.
Keith (mission scientist one): do you mean N1?
Ian: no, way point N7.
So we decided there was no real reason why going to N7 or N1 was any better than the other, so we proceeded. And in the end, we concluded that this was a sound decision and Ian should be more involved in the flight planning in future! This is because after flying for a short while within the cloud layer, we found a break and descended to our favoured low altitude. And the first leg at this level (shown below) was excellent for measuring a methane and carbon dioxide gradient! In the figure below, the methane (black) and carbon dioxide (red) shown is for the west-to-east leg shown in the flight track plot. The first half of the leg shows a gradual decrease in methane, which then levels out. This is consistent with many other flights we’ve done. This could be because there are a lot more pine trees and sandy soil in the eastern end, which are not really methane emitting.
So despite the initial confusion, and the potential for a complete wash-out, we got some great measurements which will add to those we already have. And we got home in time for dinner (back to the hotel before 7pm for once) so all in all, a most successful day’s flying!
–Dr Michelle Cain, University of Cambridge