Archive for March, 2008

Where glider is headed to

Monday, March 31st, 2008

The imagery is from the Wisconsin source Sage mentioned today. It's 30 km to get to the to get north of the upper most section of the gulf stream.

A successful weekend

Monday, March 31st, 2008

Ru15 is rounding the southern side of the warm core ring. The new waypoint and the swirl velocity will start swinging it around the western side today.

Velocities are staying low, around 50-60 cm/sec.

Temperatures remain around 15C. We are staying on the outer side of the radius of maximum velocity in the ring. We should be able to pull ourselves out this time around.
Still no satellite imagery, so we will fly by the temperature and swirl velocity record. Keep the temperatures decreasing, the swirl velocity decreasing as we head to the north. Our present set of waypoints is based on the position of the ring on March 28, about 3 days ago. Rings propagate to the west, a few kilometers a day. Assuming a relatively fast speed of 5 km/day, we may be adjusting our waypoints 15-20 km to the west over the next day or so as we move up the western side of the ring.

Closing the Loop

Sunday, March 30th, 2008

We have just closed our first loop around a warm core ring.

Temperatures are cooler on this lap. Yellows are 14 C, oranges are 16C.

Curretnt velocities are slowly decaying, but still high.
This morning we will change the waypoints and start drawing the glider out into the colder and slower parts of the eddy. This will require several waypoint changes today. If we pull too hard, we leave the eddy, and don't make our destination. If we don't pull hard enough, its another lap or we miss the target ring on the northeast.

Another Lap

Saturday, March 29th, 2008

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.

Fighting our way out

Friday, March 28th, 2008

Most recent image of the Warm Core Ring centered near 39 30 N, 63 30 W.

RU15 is in the northwest quadrant of this ring, near 40 N, 64 W. Strong currents to northeast. We are using the glider velocity to fly perpendicular to the strong eddy currents that are swirling us clockwise around the center.

Temperatures in the center (right hand side) are very warm.
We want to see these temperatures decrease as well as the currents
to indicate we are leaving the eddy on the north side.

In the Warm Ring

Thursday, March 27th, 2008

Clear morning shot of the target warm ring, and another clockwise eddy to the north showing up in the wrapping up of the warm filament.

Tempertures are up on the right had side. We are in a warm ring.

This overlay shows the clockwise currents of the warm core ring.
Our goal is to exit the warm core ring on the north west side, and jump into the new eddy to the north, spinning clockwise around it to the northeast side. Then continue Northeast in the slope water.

Free Coffee & Wireless in San Juan

Wednesday, March 26th, 2008

Warm core ring is visible near 63 30 W. 39 30 N . Cold water being wrapped around the eastern and almost to southern side.

Recent temperatues (on right) show the colder surface water about 12 C.

Speeds are up to 50 cm/sec, and direction is the east-south-east.
Consistent with entering the ring on the southeast side.

Map shows present location on the southeast side of the ring in the SST image. We should shoot around the bottom then start heading to the waypoint. Once we make that point, our objective is the warm filament on the northwest side. Something like 40 00N, 64 00 W (due north)
followed by 40 45 N 64 45 W, (towards northwest.)

Into the Warm Ring

Tuesday, March 25th, 2008

Temperature on the right hand side is warming. Up to 15C.

Currents have decreased to very slow, like 10 cm/sec.

Shows we are just entering the southeast side of the warm core ring. Looks like we made it. Object now is to continue swiming into the ring, catch the stronger currents and be swept to the west around the southern side of the warm core ring center.

From Old San Juan

Monday, March 24th, 2008

Most recent glider CTD data is on the right side of the above image. Temperatures look to be about 12 C or less. We are getting too cold. We are looking for the 15C water in the ring. We are approaching from the southeast, and the band of cold shelf water has wrapped around the eastern side of the ring. It is very clear in the next satellite shot.

Last good SST image of the targetted Warm Core Ring for RU15. Perfectly round, centered at 39 30 N, 63 39 W. A safe spot in the middle of the slope sea. Southern edge of ring is about 39 N. RU15 is getting close. We'll need to change a waypoint soon. Also look on the northwest side of the ring. That warm filament is heading northeast, towards Halifax. That warm filament is our next target. Need to think a few shoots ahead here. Just like that game Dave Martin showed us at the Pioneer Bar in Anchorage.

Here are the current speeds. Slowed down to about 20 cm/sec. Now we can fly where we want.

Here is the present location, and the small current velocity vectors. We are currently at 39 o4 N, 62 37 W. We'll need to change the waypoint sometime soon, like anytime between tonight and tuesday morning. Exact timing doesn't matter so much because of the slow current speeds. Someone can do this when they are rested. A good place to head will be along the southern side of the ring, towards 39 30 N, 64 00 W. The stronger currents are inside the ring, in the orange in the SST map which is about 18C.
If we head to this point, the strong currents will sweep us around to the west along the southern side of the ring. Could be fun.

A new route home

Sunday, March 23rd, 2008

Above Satellite image of Sea Surfact Temperature shows the Warm Core ring we are targeting to be centered near 39 30N, 63 30 W. We'll have to adjust our target waypoint to be a bit farther west once we get into the ring. But right now we want to fly to the north, so we are ok for the night. Once we are in the ring, the currents will spin us clockwise around it, and it will be a natural adjustment to fly toward 63 45 W. it looks like the southern side of the targeted warm core ring is at about 39 N, and RU15 is just south of that location. We should begin to see the temperatures warm and the currents spin around to flow to the west. Once that current switches direction, we switch the waypoint.

Once RU15 is in the ring, we see the new exit point now on the northwest side. The idea is to leave the ring where you see the warm (yellow) water heading towards the shelf break. This region will have favorable currents. The cold (blue) water is shelf water, and unfavorable currents for our northward journey.

Above is the temperature section. Most recent data on the right. You can see the warming as we head north out of the Stream into the ring.

Above are the current vectors for the last 2 days. You can see the sharp decrease as we leave the Stream, and now the currents are starting to turn. The present waypoint if perfect for now, perpendicular to the currents, pulling us northward into the ring. As soon as the currents switch direction and flow to the west, likely sometime tomorrow during the day, we will switch to a waypoint on the west side of the ring. The current waypoint is on the east side. The new waypoint will be somethin like 39 30 N, 63 45 W. The idea is to put this point on directly west of the ring center, and more than 2/3 of a ring radius out. Because the ring is moving west, subsequent imagery may make that new waypoint as far as 39 30 N, 64 00 W.

Here are the current speeds and directions. Still above 0.5 m/sec, about twice the speed of the glider. So there is no way to fly against this current. We have to use the currents to our advantage to advect us in the directions we want to go, and use the glider speed to move us from one favorable current to another. It is a different way of flying.