Saturday, March 29, 2008

Another Lap

Most recent sst imager indciates the warm core ring with RU15 in it is underneath the cloud cover (white), but the small eddy to the north that is our target is still there. Its centered near 41 N, 64 W and you see the laternating warm and cold bands wrapping around in a clockwise direction.
RU15 couldn't make it out of the ring yesterday on the northwest side yesterday, so Hugh sent it on another lap around. We'll try to stay closer to the edge and exist a bit sooner this time around.

Current speeds are diminishing. So we are making our way to the outer edge of the warm core ring.

Unfortunately we are under the clouds (white in the image) so we don't have a map from today to fly by.

But we do have a map from two days ago. Present glider location is 40 05N, 63 22 W, so we are moving out of the red core of the ring and into the yellows which are about the 14-16 C range.

We seeing cooling in the right hand side of the glider section to the same 14-16C temperature range.

Right now our target waypoint is 39 20 N, 63 30 W. Fine for the overnight shift while we are at the north side of the ring. We just want to start sweeping around to the south, and the swirl will do most of that for us.
As the day goes on, we will want to shift that point farther out in the ring. Right now it is inside the warm center and inside the first lap we took around.
In this case, instead of flying towards a point, we want to fly away from a point. In this case the point we want to fly away from is the center of the eddy. This is a new and interesting behavior for a glider. We care most about using all the glider velocity to go away from the center and we care less about where the swirl velocity takes us. We can time our exit to sweep us around to about where we want to be.
RIght now we can only fly towards a waypoint, so to accomplish this most effectively right now, we would have to set a new waypoint outside the eddy every time the glider surfaces, which is a bit impractical on a long duration mission. So lets try this by setting four waypoints between here and where we want the glider to be on the other side sometime sunday or monday.
1) 39 30 N, 63 00 W, outside the ring in the cold 6C filament wrapping itself around. When we get close, say within 20 km, we switch to:
2) 39 00 N, 63 30 W, just on the southern side of the ring, and on the outer edge. Again, when we get to close (say 20 km), we switch to
3)39 30 N, 64 45 W, at the easter side of the ring, possibly pulling it out. If the temperatures are staying warm and velcoties high, we will have to adjust this point west a bit, say another 15 minutes to 65 00 W. We can make that call as we round the southern side. Then we go for the base of the new eddy and fly up its wester side buy going to
4) 41 00 N, 65 00 W.
Lets give something like this a try over the weekend.

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