INDOEX C-130: FLIGHT 17, 24 March 1999 Objective: Clean Cloud Indirect Forcing Mission Scientists: B. Gandrud and A. Bucholtz Summary: The primary goal of this 9hr 29min mission was to measure the radiative and microphysical properties of clean clouds south of Male below the equator. While meteorological conditions seemed marginal in the morning before take-off we managed to find a nice deck of low-level clouds at approximately 7.25S, 72.6E to 70E with only thin cirrus above. We flew a stacked, multiple-altitude pattern with legs high above the cloud deck, in the clouds, just above the cloud, and a few hundred feet below the cloud. Spiral profiles were performed at each end of the stack. This cloud field started out as one of the nicest stratus decks we've seen this experiment. Some dissipation and advection of the clouds occurred during the time it took to complete our measurement stack but the clouds remained substantial. Dropsondes were launched every 2 degrees from the Equator to 8S on the ferry down, and from 6S to the Equator on the ferry home. A dropsonde was also dropped over Hulule from altitude as we returned. UTC --- 03:30 (8:30 LST) Taxi 03:34 Take-Off; Ci shield above; cu, convective cu below 03:59 (15000ft; 2.97N 73.5E) Ferrying south; nice huge cirrus shield above; scattered stratocu, cu, convective cu below 04:12 (15000ft; 2.08N 73.5E) Cirrus shield above; scattered cu, convective cu below 04:14 Hung and Brett have good brown cloud image to west taken @ 2N 04:20 (15000ft; 1.57N 73.5E) Ci starting to break up above; some convective cells around; scattered convective cu streets below 04:39 (15000ft; 0.24N 73.5E) Nice ci anvil coming up ahead; clouding up ahead; clear to scattered stratocu streets below 04:40 Could be good diffusion regime case, has some precip 04:45 Lidar reports ci anvil above @ 7.5 km; entering convective cu cloud 04:49 (0.5S 73.5E) Just passed through convective cu cloud (with rain); broke out; dark ci anvil above; clearing below; scattered cu in area 04:51 0.6S and still see brownish haze below us 04:55 actinometer just turned on now so cloud passes of no value for diffusion regime 05:01 (15000ft; 1.3S 73.5E) Ci anvil cloud above; scattered streets of convective cu below 05:03 Entering cloud 05:04 Inside, but near bottom of cloud; can see clouds below 05:05 Broke out of cloud 05:16 (15000ft; 2.3S 73.49E) Cirrus thinning but still mostly overcast ci; scattered, slightly convective cu below 05:24 (2.84S 73.5E) Broken ci above; scattered, small cu field below 05:32 Ops Center report: Keep going to original waypoint; should break out from under ci @ approx 5.5S 05:34 (15000ft; 3.6S 73.5E) Overcast to broken ci above; scattered cu below 05:40 Dropsonde; lidar report: indefinite haze layer top at approx 2.5 km; cloud tops approx 800-1000 m 05:42 (15000ft; 4.1S 73.5E) Overcast to broken ci above; scattered but increasing cu streets below; Steve reports practically no refractories at this altitude; haven't seen it this low; essentially zero refractories < .4 microns; SO2 reasonably high; CO relatively high... this suggests relatively polluted air that's been cleaned of particles 05:50 (4.6S 73.5E) Lidar report: top of haze layer at 2.4 km, thin layer at approx 3 km 05:58 (5.1S 73.5E) Mostly solid ci shield above; scattered, increasing cu to slightly convective cu streets below 06:03 (5.6S 73.5E) Ci shield above (seems to be thinning, breaking up ahead); scattered cu streets below 06:16 Steve reports: CO down near detection limit; SO2 also dropped; aerosol about the same...implies this may be southern air 06:39 (8S 73.57E) On suggestion of Ops Center we're turning to head to 7.25S 72 40'E to run line from 72 40'E to 70E; Dropsonde a couple of minutes ago 06:43 Thin to moderate ci above; scattered cu, convective cu below 06:45 (7.9S 73.25E) Paralleling convective line to our North 07:04 (7.089S 72.666E) Thin ci above, nice... start run, Hung has several images 07:07 Re-aligned heading for better cloud line 07:13 (6.95S 72.14E) Thin ci above; broken stratus deck with some cu below -> beautiful! 07:18 (6.9S 71.79E) Thin ci above; dense popcorn cu below 07:23 (6.8S 71.5E) Passing over some mid-level, dark (water?) altostratus 07:26 (6.73S 71.34E) Steve reports: CO looks dead. End leg; spiralling down 07:31 Passed through some mid-level cloud @ 11000ft 07:33 (8500ft and descending) Spiralling over some island atoll 07:-- (6500ft and descending) Scattering coefficient starting to increase 07:37 Peak @ approx 5300ft in haze layer 07:39 Cloud tops approx 3900ft 07:42 Cindy reports droplet concentrations low...suggests clean clouds 07:43 Cloud base approx 1800ft (still spiralling) 07:44 Cindy reports wind speed approx 5 m/sec, looks very clean down here, blue sky "see forever" 07:45 (100ft) Starting spiral up to just above cloud tops 07:50 (6000ft) Start 20 min just above cloud run 07:53 Skimming through tops of cloud (pilots turning plane for some reason?) 08:00 Maneuvaring to stay above clouds 08:07 (6.9S 72.6E) Clouds below have dissipated or advected to North! 08:-- (6.9S 72.9E) End leg; turning North to find clouds 08:17 (6.55S 72.85E) Turning to West; descending into cloud (parallel our previous course) 08:19 Starting in cloud run at 1960' 08:22 Going in and out of convective cu 08:31 (6.3S 72.14E) Going in and out of convective cu 08:40 (6.2S 71.7E) Going in and out of convective cu; Where did that nice stratus deck go? 08:50 (6.03S 71.2E) End leg; turning to reverse track and descend to 1000ft 08:53 (1000ft; 6.1S 71.2E) Start below cloud run at 1000 ft, clouds showing shadow on ocean surface 08:57 Scattered, slightly convective cu above; thin ci above that 09:05 (1000ft; 6.3S 71.9E) Scattered, slightly convective cu above; thin to moderate ci above that 09:18 (1000ft; 6.5S 72.5E) Scattered cu starting to thin out 09:24 End leg; spiralling down to 100ft 09:27 (100ft; 6.63S 72.96E) Start spiral up 09:44 (9100ft and climbing) Still spiralling up 09:56 (15000ft) Starting to ferry home 10:02 (15000ft; 6.3S 73.3E) Solid ci above; scattered popcorn cu below 10:13 (15000ft; 5.5S 73.4E) Dropsonde back at 6S; thinner, but still moderate ci above; clear to scattered cu below 10:22 Seem to be headed NW rather than N, appears something wrong on flight deck, finally corrected course after update from science GPS 10:32 (15000ft; 4.2S 73.3E) Moderate ci above; clear to widely scattered small cu below 10:35 (4S 73.3E) Dropsonde; winds shifting from strong out of the west to more Northwest 10:48 (3.12S 73.4E) Wind shifting to more out of NNE; moderate ci above; scattered cu, convective cu below; XCNHOT increasing, XCNCOLD decreasing, correlated with change in wind direction 10:57 (2.5S 73.42E) Wind shifted to NE (almost 180 deg change from down south); thin to moderate ci above; scattered convective cu below 11:11 (1.5S 73.5E) Dropsonde launched back at 2S 11:21 (0.92S 73.5E) Winds shifted around again to coming from the W 11:31 Winds shifted back to coming out of the West; XCNHOT and XCNCOLD decrease correlated with wind change 11:35 (0.03S 73.45E) Dropsonde; problem with plane's nav computer caused us to drift off course twice on return ferry home. 11:37 HotCN continuing to rise as we proceed N 11:40 (15000ft; 0.37N 73.42E) Ci above; scattered convective cu below 11:50 (15000ft; 1.13N 73.5E) Thick ci, cirrostratus above; scattered convective cu below 12:07 (15000ft; 2.2N 73.5E) Heavy ci above; scattered cu below 12:25 (3.4N 73.5E) Thick, dark ci anvil above (cell off to our right); scattered convective cu below 12:36 (15000ft) Dropsonde over Hulule; start spiral descent 12:51 About cloud top altitude in slow long descent 12:52 HotCN still climbing 12:54 Pass through cloud, and water sensors show wetting 12:58 Gear down, clouds in descent 13:03 Land, rain on runway 13:07 Block time Debrief: Cindy: Everything went well; good, clean clouds (some of the cleanest); She got enough samples Ann: Everything ok; signal was low because air was clean Olga: Everything went ok, but concentration were low Hudson: Everything went well, everything worked; good clouds Steve: OPC worked; all Clarke's instruments worked; thinks clouds may not have been pristine, but they were clean; CO instrument dead; Anderson's instrument ok; Porter's instrument ok Brett: Everything worked ok Detliv: Mass spec worked ok Rick: SABL looked good (both channels); AIMR ok Errol: All dropsondes good (3 bad sondes found before dropping); will have 3 sondes left after today George: MCR chan 6 dead; all other channels ok; WINDS/DSM ok, just some minor glitches