TIME (UTC) REMARKS
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20:20 Takeoff and ferry to site at 18,000'
21:40 Identify cloud to sample at 41.4S and 141.13E.
21:57 Spiral down in detrainment side of cloud.
22:18 Stop spiral at 8,000' and cross to upwind side for spiral up
to 16,000'. Cu tops at 15,000'.
22:43 Start upwind descent at 100'/min to surface en route to Cape
Grim. CN and CCN generally lower in RH conditions.
23:02 Start 15 min leg at 1000' en route to Cape Grim along wind from SW.
23:09 Drizzle for 20sec.
23:18 Drop to 300' for 20 min leg to Cape Grim.
23:34 Immediately North of Cape Grim. Squalls to left and right.
40.6 S and 144.75 E. Continue on for 5 min cal leg at 300'.
23:44 Hit our exhaust
23:48 Drop to surface and commence slow climb near Cape Grim for
vertical profile at about 250'/min in MBL.
23:57 In/between cloud.
00:18 Find cloud at 13,500' near Cape Grim. 40.12S 144.43E
00:56 Break away from cloud to avoid being over land.
01:12 Drop to altitude of older cloud tops.
01:26 Probably hit our exhaust.
01:42 Porpoise in and out of layer.
01:59 Turn and climb to 9,000 heading SW from Cape Grim.
02:33 Circle older Cu at -40.8S and 142.9E.
02:34 Circle over cloud free region and descend with 20deg bank
to surface for satellite intercomparison and -40.8 S and 142.9 E.
02:43 Satellite overpass
03:02 End surface circle at 300', climb and move southwards.
03:18 Fly nuclei layers near old cloud remnants.
03:49 Near cloud top in dry air, low particles and gases.
03:59 Drop into mist air near clod top and nuclei and gases
increase markedly.
04:06 Investigate detraining tops at all altitudes.
04:25 Try and stay in layers - not easy.
04:35 Climb to cloud top and descend to surface.
05:05 5min level leg at surface.
05:09 end 100'leg and climb and return to Hobart.
05:15 Fly upwind at detrainment altitude 1/2 hr, lidar profile.
05:30 Turn, drop to surface and climb on return leg (40min)
06:10 Profile upwind and downwind cloud regions (1hr.)
07:10 Optional studies/time allowance (50min)
08:00 Return to Hobart (1hr)
09:00 Touchdown
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This mission was directed at identifying particle production in the vicinity of cumulus clouds. We were successful in our objective of finding clouds to the west of Tasmania with tops near 12,000 to 16,000 ft. and which were relatively higher than the majority of the cloud field further west. This allowed identification of the onset of particle production associated with cloud processed air in air that had little modification by previous convection. Air at cloud top was characterized to the west and downwind of the detraining tops in order to determine if particle enhancement is present in the detrainment region. A comparison of early morning and afternoon flights indicated that neither ultrafine nuclei nor aerosol precursors such as sulfuric acid were present in the morning but that both increased in the detraining region of clouds as the day progressed and photochemistry became more active.
Numerous circles around individual clouds, layer characterization and vertical profiling were completed. The focus was on changes apparent in the ultrafine nuclei and species likely to be involved in that process. The data suggest that prolific new particle production occurs in the vicinity of cloud outflow regions at various altitudes following the onset of significant photochemistry. Ultrafine panicles first became conspicuous in late morning measurements and increased during the early afternoon. Particle growth also appears to occur rapidly in the thin outflow regions and associated layers. A relative decrease in ultrafine particles in the later afternoon was suggested along with an apparent "aging" of the "new" distribution. In contrast, CCN in these regions were often quite low. The data reflect the dual role of clouds in reducing the existing larger nuclei concentrations through in cloud processes while replenishing particle number through particle production in the outflow regions.
Between the two cloud comparisons periods we diverted to Cape Grim for the second objective of an instrument intercomparison and vertical profile. We descended from altitude upwind of Cape grim and flew for about 15 minutes at about 1000' and about 20 minutes at 300'on a trajectory corresponding to the wind direction advecting air to Cape Grim. This was followed by a slow climb (about 250'/min) in the boundary layer immediately North of Cape Grim for establishing a vertical profile in the Cape Grim area. A variability of about 20% in concentrations were seen along the flight legs and precipitation from squall showers were occurring in the vicinity of Cape Grim with winds of about 10 m/s. Hence, the structure in the 20min 300' leg should be reflected in the structure in the subsequent 5-6 hour sampling carried out at Cape Grim.
A third objective was a satellite calibration that included a vertical profile and banked circles flown in clear air during a satellite overpass at 02:43 GMT.