TIME (UTC) REMARKS
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1930 Takeoff Hobart, climb to 18,000'
1954:00-2053:00 Nominally level at 18,000' southbound
2037:30-~2043 Porpoise slowly to 17,000' to look for layering
2019 Acquired two balloons, with third shortly thereafter
2053 Dropped rapidly through altostratus layer to avoid icing
2058:32-2113:05 Lidar leg southbound at 10,000'
1000 fpm descent to 5000', then 500 fpm to 100'
First Stack
Registered to balloon #0
2130:29-2200:29 CW 30 min Lenschow circle at 100'
Start 49:40 147:17
2124 #0 at 49:48 147:23
2132 #8 at 49:49 148:04
2131 #6 at 49:50 146:56
90/270 climb to 500'
2204:06-2234:06 CCW 30 min Lenschow circle at 500'
Start 49:53 147:11
2204 #0 at 50:08 147:34
90/270 climb to 2000'
2238:00-2308:00 CW 30 min Lenschow circle at 2000'
Start 50:09 147:21
2239 #0 at 50:26 147:44
90/270 climb to 4000'
2311:08-2341:08 CCW 30 min Lenschow circle at 4000'
Start 50:25 147:29
2314 #0 at 50:45 147:54
90/270 climb to 7000'
2344:54-0014:54 CW 30 min Lenschow circle at 7000'-also used as lidar leg
Start 50:40 147:46
2344 #0 at 51:02 148:05
0014:54-0027:00 Spiral descent at 1000 fpm to 5000', then 500 fpm to 100'
Second Stack
Reregistered to balloon #0
0028:21-0058:21 CCW 30 min Lenschow circle at 100'
Start 51:20 148:16
0029 #0 at 51:24 148:15
90/270 climb to 500'
0102:43-0132:43 CW 30 min Lenschow circle at 500'
Start 51:32 148:20
0104 #0 at 51:40 148:22
0101 #8 at 51:33 148:54
0056 #6 at 51:37 147:31
End 51:47 148:17
0134 #0 at 51:55 148:25
0132 #8 at 51:48 149:00
0131 #6 at 51:56 147:34
Exhaust Charactrization Leg
0134:00-0139:00 Downwind leg at 500' to generate exhaust
90/270 turn
0142:20-0147:20 Upwind leg at 250-500' to look for exhaust
One brief CN spike at start
0144:00-0144:15 100 ppt NO spike, with elevated CN from exhaust
~0147:20 50 ppt NO spike from exhaust
Spiral ascent to 7000'
0154:38-0205:38 Lidar leg north across circle at 7000'
0205:38 Climbout directly toward Hobart
0217:45-0356:55 Level at 18,000'
Descent into Hobart
0427 99Landed Hobart
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We had no trouble acquiring the balloons on our ferry south, since they were slightly north of the predicted location. This may be due to the fact that they spent much of the night at a very low altitude, evidently skipping their ballasts on the water. It may also be due to the dramatic wind-shear we noticed, in which the 100' winds were northerly at about 20 knots, while at 1600' (the balloons' daytime altitude) they were from 330 at 30-40 knots. Since the three balloons were in virtually the same orientation relative to one another as they were when launched, we elected once again to start our stack with the south edge of our circles a few miles north of balloon #0.
A thick deck of altostratus covered the entire study area. Since it contained icing conditions, we dropped through it as quickly as possible before starting our lidar leg over the circles. We found that less than half the study area contained low cloud. A sounding identified at lest three layers in the boundary layer, with the strongest dryout at about 6000'. Lesser inversions were evident around 4500' and 2000', with a few clouds between 1000 and 2000'. During the first 500' leg we saw what appeared to be showers to the southwest of the circle, but never encountered any precipitation at the plane.
The first stack included legs at 100', 500', 2000', 4000', and 7000', to have two flux legs in the surface mixed layer and one each in two elevated layers and in the free troposphere. During our lower-altitude legs the balloons (at 500-600 m) moved away from our advecting circles, but we kept pace at the higher alittudes. The first stack began 10 miles north of balloon #0, but with more experience we were able to start the second stack just four miles north of #0. At the end of the lidar leg, we estimated the time our 500 fpm descent would take, and projected the balloon's location to that time. Then we began our descent by moving to that position, and did a spiral descent there which ended with the proper heading for the start of the circle. Descending in place and then correcting the position while at 100' (as we had done earlier) introduced a time-delay which it was difficult for me to calculate while orally receiving reports of new balloon locations and instructing the pilots on new targets. All these calculations were done manually.
It would be a simple matter to write software which would use continually-updated locations for the balloons and the plane to direct the pilots to the next start location. Our inability to get that and other circle-flying aids programmed into the plane's data system can be traced directly to a UCAR personnel policy which cost RAF one of their best software engineers at a critical time prior to ACE-1. When forced to prove his worth, he received more generous offers, one of which he accepted. Although it may seem off the point in a flight report, that policy had a direct, negative impact on our ability to implement the most sensible technology to fly these missions.
We had time for two circles in the second stack, and flew them at 100 and 500'. This stack began four miles north of balloon #0. We finished with a lidar leg across the circle, just before our return.
Between the last circle and the lidar leg, we made an effort to sample our own exhaust, to support later studies of the extent to which we may have polluted the study air. We flew a directly-downwind leg for 5 minutes, did a 90/270 turn to a point on that leg, and flew back upwind. Since exhaust tends to sink, we porpoised a bit between 250 and 500' above the surface. Immediately upon starting the upwind leg we encountered a very brief spike. We had two more encounters, of 15-20 seconds duration, one at the very end of the upwind leg. The encounters were characterized by elevated NO and aerosol concentrations. Unfortunately, because of the transient and unpredictable nature of the encounters, the timing of UCI's cans may have just missed sampling them for organics.
We are very pleased to have conducted four flights in the same postfrontal air. While it is clear from the altitudes and trajectories of the balloons that 1) they slowed somewhat at night due to skipping their ballast-floats on the water and 2) they moved more rapidly than the surface-layer air in the daytime when they flew near the first inversion layer, the fact that they maintained their relative positions so well and traveled at approximately the forecast speed gives us some confidence that we were studying the same general airmass that we started in. Preliminary chemical and microphysical evidence also support this view. It may be that the large size of the clear patch in which we began the experiment kept the balloons from sliding into an airmass with a significantly different history.
If the resulting chemical data demonstrates the worth of this approach, we need to think about whether a smart balloon can be developed which can be targeted at 200m without unacceptably raising the risk of putting it into the water. When planning the launches, we found ourselves in conflict over this issue: we wanted to tag the lowest mixed layer (whose fluxes and chemistry we were actually studying), but needed to target the balloons at a minimum of 500 m to try to keep them dry. As it happens, they clearly spent the night at the surface anyway, moving slightly slower than the in situ winds.