APPROX.
TIME COMMENTS
(UTC )
23:01 TAKEOFF and climb to 20,000 over Tasmania
23:34 Climb to 20,500 to get out of cloud top
00:09 at 40.78S 144.40E - Contact transponder from ship.
00:22 Start descent to surface near R/V DISCOVERER
00:39 at 100' and climb to 1000'
00:40 Start 18 min leg at 1000'
00:58 Climb to 20,000'- UCN & gases elevated in layer near 10,000'
01:25 Descend to 10,000'& head South trying to stay in layer with UCN about 1200/cc
01:46 Start 5min leg in 12,300' layer near 42.5S and 143E.
01:49 Interesting plume like structure in boundary layer lidar suggestive of shear driven
mixing up of moist layers near surface?? Also observed later in flight.
01:54 Start 5 min leg at 12,150'- lower UCN concentrations.
02:16 Descend to 6,500' through thin layer and climb back into it.
02:25 Flying UCN layer between 6,000 and 8,000' in moist air below dry.
02:38 Start 5min leg @ 6,300'
02:48 Start 8min leg @ 7,500'
02:52 End leg near 41.6S, 143.6E and descend to 100', wind from west.
03:11 At 100' for 1min then climb to 1000' near ship.
03:15 Start 1000' leg below cloud - ship reports trimodal distribution at 15, 30 and
110nm diameters. They estimate air is 30% cleaner than previous ship
intercomparison but not truly clean air. C-130 CN=600 to 800/cc.
03:31 End 1000' leg near 41.6S and 143.7E, turn and head west and climb to 15,000'
03:54 Over cloud top.
04:18 Two enhanced UCN layer near 11,000'-13,000'
04:26 15 deg. banked turn from 270>360>90 deg. at 15,000'and 41.7S - 140.6E.
04:29 Start descent from 15,000' at 1000'/min towards east.
04:35 Three enhanced UCN layers 9,000'-12,000'at cloud level.
04:50 At surface start 1min 100' leg.
04:52 Climb and start 1000' leg for 15min.
04:54 4-5 times ammonia at higher altitudes reported here.
04:58 Lidar reported layers and plumes that appear to be mixing up from surface layer.
05:10 Turn to west and climb to 18,000'near 42.6S and 144.9E,
05:19 Cross three thin UCN layers (UCN 4,000/cc) between 7,000 - 9,000'.
Two smaller layers (UCN=1000/cc) near 11,500' and 15,500'.
05:32 Stop climb at 18,000, at 42.3S and 143.5E and descend.
05:45 In UCN layer at 10,700'. THETAE=296.6
05:56 Get in layer at 11,700 for 5 min leg. UCN up to 6000/cc.
06:21 Approaching group of largest and highest (est. 14,000') well developed Cu with
anvils that we have seen. UCN increasing during approach.
06:25 Next to Cu at -41.73S and 140.18E. Circle cloud counterclockwise starting from
North side.
06:39 Climb above downwind detraining region on SW side. UCN drop.
06:44 Not high enough. Climb to 14,000 for another pass.
06:51 Finish 14,000' pass and descend. Some UCN elevated near outflow at 13,000' but
much higher in 9,000'-12,000' outflow altitudes.
06:56 Make pass through cloud droplet haze of outflow, UCN stay high except in most
cloudy region.
06:58 Descend to about 4,000'below outflow, UCN drop to about 800/cc.
07:02 Climb and encounter UCN (6000/cc) near 8,000, and continue to about 10,500'into
core of outflow and head downwind toward Hobart. Wind 20m/s.
07:20 Maneuver to stay in layer.
07:27 Divert from downwind to head due east to Hobart away from Cu.
07:46 Flying over more cloud free region and UCN start dropping.
07:58 Pass over coast.
08:23 LAND
This mission was chosen to explore the hypothesis that the free troposphere may be a source region for new particle production and that this production may be associated with cloud processes. A weak front and post frontal conditions were present in the vicinity of the R/V Discoverer located near Cape Grim at the start of the experiment. This prompted the mission to start with early comparisons to ship board measurements and vertical profiles in that region. The previous shipboard observations of small nuclei in post frontal subsidence also prompted this rendezvous. The first ship encounter was made in post frontal conditions near 00:20GMT with some evidence for small nuclei above and in the boundary layer but the ship also reported some indications of continental air based upon soot measurements.
The C-130 then diverted further south to reach cleaner air before returning to the ship about 3:00GMT. Vertical profiles were flown and nuclei layers encountered near 10,000'. The second encounter with the ship was in cleaner air but the ship still claimed some evidence of soot in the area.
In order to reach cleaner and colder air with deeper convection the C-130 left the ship and headed further south. Deeper and more widespread cumulus towers were encountered with clear outflow regions around 11,000'. These were characterized and showed pronounced nuclei at concentrations of about 6,000/cc with enhanced ultrafine nuclei in the 3-4nm range. These outflow region was followed downwind until the C-130 had to divert track for return to Hobart.
In brief, evidence for enhanced nuclei in cloud detrainment regions and cloud top were found at all locations. These concentrations typically exceeded those both below cloud base and above cloud base, suggesting that the origin was related to the cloud detrainment region. The high concentrations and small sizes suggest that nucleation was both recent and fairly rapid under these conditions.
Here we define UCN to be all particles observed by the C-130 CN3025C counter detecting particle diameters above 3nm.