TIME (UTC) REMARKS
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0233 Takeoff Hobart, climb to 18,000'
0257:45-0352:45 Level at 18,000'
0309 Disco at 41:17.6 S 139:09.5 E
1000 fpm descent to 10,000'
0400 Disco at 41:19.0 S 139:05.5 E
0402:00-0411:54 Lidar leg, across circle at heading 330
(like satellite)
Start 41:30 S 139:32.9 E
End 40:51.6 S 139:00.6 E
0411:54-0426:55 90/270 turn and 500 fpm sounding to 100',
heading 150
0428:14-0458:14 CW 30 min Lenschow circle at 100'
Start same as lidar leg above, 240 heading
Rapid climb to 5000' at 330 heading for
satellite intercomparison
0500 Satellite directly overhead
0501:28-0505:28 5000' leg at 330 heading
500 fpm descent to 500' leg
Start of pattern displaced 5 miles east:
41:28.2 S 139:39 E
0518:37-0548:37 CCW 30 min Lenschow circle at 500'
90/270 climb to 1200'
0551:40-0622:40 CW 30 min Lenschow circle at 1200'
Imperfect circle; display locked up
90/270 climb to 2000'
0625:56-0655:56 CCW 30 min Lenschow circle at 2000'
Possible data loss due to tape drive problem
on this leg
90/270 climb to 4000'
0659:00-0708:30 Porpoise leg across circle at 330 heading
0710:51-0740:51 CW 30 min Lenschow circle above inversion at 4500'
0741:03-0750:30 Spiral 500 fpm sounding to 100'
0750:30-0805:10 100' level leg east of Disco to new set of circles
~0802 Passage through Disco's plume
0805:10-0835:10 CW 30 min Lenschow circle at 100'
Start 41:35 S 138:51 E
90/270 climb to 500'
0838:14-0908:14 CCW 30 min Lenschow circle at 500'
0909:00-0916:20 Spiral sounding from 100' to 5000'
0916:20-0927:30 Porpoise leg southbound across circle at inversion
Spiral climb to 10,000'
0931:45-0942:00 Lidar leg at 10,000', northbound across circle
Climb to 17,000' enroute to Hobart
0909:50-~1032 Level at 17,000'
1032-1059 Porpoised a bit between 15,000 and 19,000' looking for UCN
1059 Descent into Hobart
Landed Hobart
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We conducted what appears to have been a very successful clear-air column closure experiment, a flux method intercomparison, and an instrument intercomparison with Disco on this flight. As we dropped into the study area we crossed a wide cloud-free area and saw Disco at the far western edge of it, just under a layer of broken cloud. We located our first patterns in clear air to the east of Disco. Based on a report of winds at 5 knots from 170 degrees at Disco and our desire to sample nearly the same air as the Disco, we began our circles 15 miles upwind, so that their western edge would be 5 miles from Disco at our closest approach (at the start of the second stack). When we learned during the first circle that Disco was moving eastward (on a heading that facilitated a radio transmission), we relocated the rest of that pattern 5 miles farther eastward to avoid polluting the ship or vice-versa.
The column closure included a 10,000' lidar leg immediately under the satellite track less than an hour before the overpass, slow boundary layer profiles just before and after the overpass, 30 minute circular patterns (at four altitudes in and one altitude above the boundary layer) bracketing the time of the overpass, and a four minute level leg above the boundary layer immediately under the track, within two minutes of the view. The TDDR and John Porter's downward-looking camera were operational, and Disco's nearby sun photometer made readings each 15 minutes to get an independent measure of optical depth.
Conditions were not ideal for the flux intercomparison, because of low windspeeds. During the first patterns the winds were often only 1-3 m/s. That means that the DMS fluxes were probably quite small, even though we located the experiment over relatively high-DMS waters (~3 nM). Of greater concern was that the wind direction shifted during the first stack: The light winds became westerly, meaning that Disco's plume passed directly through our circle. We did see brief spikes on some circles, which sometimes included CN, ammonia, and occasionally NO. Since the ship did not emit DMS and since the times of the spikes are evident and can be removed from the data of most instruments, the flux objective was probably not affected by the exhaust.
However, the ability to collect integrated samples of NSS for studying the clear-air sulfur budget was potentially compromised, so we moved the second stack to the south of Disco, into an area which became cloudier as the afternoon progressed. The windspeeds were considerably higher for this stack, however (3-7 m/s), so the DMS fluxes should have been greater than on the first stack. On our way from the first stack to the second, we made a very close 100' pass by Disco, to permit an intercomparison of microphysical and radiation instruments.