INDOEX C-130: FLIGHT 18, 25 March 1999 Objective: Bay of Bengal Mission The Last INDOEX Aircraft Mission Mission Scientists: B. Bush and V. Ramanathan Objective: To sample aerosols and clouds in the Bay of Bengal region for comparison with the Arabian Sea aerosols The region for in-site sampling extended from [4.5N,85E] to [7.5N,87.5E]. Four level flight legs were done in north/south directions at 87.5E between approximately 5.5 and 7.5N. On the in-bound (return) flight, cloud micro-physics measurements were conducted for about 45 minutes between [5.5N,87.5E] and [4.1N,85E]. Finally, a slow descent from 18,000 feet was made on the approach to Male' with a final 20-minute level flight boundary layer leg at 100 feet and with a climb to 8,000 feet for a 45-minute "in-haze" leg. This later leg ended up be half clean and half polluted due to the prevailing winds at that level. The aerosol conditions can be described as typical of a moderate level of pollution. We were quite successful in finding the polluted air and sampling at 4 levels. The aerosol was quite well mixed from the surface to about 1.5 km. North/south gradients were also quite small. In the equatorial Indian Ocean west of 85E, we sampled plenty of low-level clouds for about 45 minutes. During the middle of the run, the wind changed direction from northerly to southerly accompanied by a drop in aerosol scattering coefficients, CN, CCN, and other parameters. The following is a chronology of the mission: Alt Lat Lon UTC ft N E Comments ------------------------------------------------------------------------------ 03:33 4.2 73.5 Take-off at Male'; climbing and heading east. 03:55 4280 4.1 74.6 Still climbing 04:00 WINDS display is frozen 04:05 5234 4.05 75.2 Leveling off at 17000 feet 04:10 5238 4.04 75.53 04:16 5235 4.03 76.02 Lots of low level stratocumulus clouds below 04:17 5231 4.03 76.07 Approaching cirrus 04:22 5232 4.01 76.36 Stratocumulus tops from 0.5-1.0 km (some up to 2.0 km) 04:30 5229 3.92 76.87 Flying into strong head wind 04:35 5225 3.87 77.22 Aerosol layer top at approximately 3.0 km 04:48 5229 3.85 78.16 Approaching thick cirrus (mostly clear and hazy below) 05:00 5230 3.79 78.92 Some scattered clouds in haze below; broken cirrus above 05:05 5231 3.78 79.32 Cirrus thickening overhead 05:15 5234 3.76 80.00 Cirrus is uniform and thick 05:21 5233 3.74 80.35 Approaching some low level clouds 05:30 5232 3.69 80.92 Some breaks in the cirrus; still scattered low clouds 05:32 CN hot/cold ratio jumped to 0.5 05:38 5236 3.64 81.60 Cirrus thinning; low level clouds increasing 05:53 5234 3.63 82.60 Still scattered below; mostly uniform cirrus above 05:55 5232 3.62 82.71 CN ratio went back down (Rh increased, too) 06:04 5232 3.58 83.10 Cirrus getting thicker above; low level decreasing ahead Hot CN has some temporary increases 06:08 5236 3.55 83.66 Cirrus and low levels clouds seem anti-correlated 06:14 Might be skimming the top of the haze layer? 06:15 5238 3.58 84.19 Turned toward [5.5N,87.5E] 06:23 5235 3.86 84.60 Clearing ahead above; low clouds below 06:30 5242 4.09 85.00 Very little scattered cirrus above 06:41 5238 4.45 85.67 Still clear above; varying degree of cloudiness below 06:42 Top of haze approximately 3.5km (very thick) 06:47 5236 4.71 86.09 Approaching cirrus ahead 06:54 5233 4.93 86.46 Cirrus above; a few low clouds below 07:01 5237 5.21 87.00 Cirrus thinning ahead 07:11 5237 5.57 87.49 Start 20 minute leg at 17000 feet 07:12 Dropsonde #1 07:13 A few scattered clouds below 07:14 5231 5.71 87.49 Aerosol layer top at 3.5 km (not distinct) 07:15 5231 5.88 87.49 Cirrus is clearing above 07:17 5231 6.01 87.48 Cirrus is increasing a little 07:23 5234 6.43 87.45 Dropsonde #2 07:26 5233 6.64 87.44 Still light cirrus above 07:31 5233 6.95 87.42 Dropsonde #3; Puffy cloud tops at 1.0 km 07:32 5233 7.01 87.42 Starting descent to 100 feet 07:34 4450 7.18 87.40 Clear above; scattering coefficients are low 07:36 3600 7.09 87.30 CN is slowly increasing 07:39 2700 7.01 87.41 Scattering coefficients are still small 07:40 1576 7.04 87.60 Top of aerosol layer 07:43 SABL is looking up 07:45 700 7.14 87.50 Cloud level; uniform aerosol layer below 4800 feet 07:47 70 7.03 87.50 Starting 100 feet leg going south 07:48 70 Under some clouds periodically 07:49 WINDS display is frozen 07:51 70 6.83 87.50 Hazy above with some clouds 07:59 70 6.35 87.47 Not many low clouds, but some upper level clouds 08:05 WINDS display is frozen 08:07 End 100 feet leg - climb to 2300 feet 08:10 Level at 2800 feet 08:13 907 6.02 87.50 No clouds ahead 08:18 901 6.32 87.49 Fairly uniformly mixed layer 08:21 900 6.51 87.49 A few clouds approaching (change heading to sample) 08:26 Sampling clouds 08:31 900 7.06 87.56 End 20 minute "cloud" leg 08:34 1278 6.93 87.51 Starting above cloud leg 08:36 1271 6.83 87.51 Some cirrus above us 08:43 1269 6.37 87.50 Scattering is increasing 08:50 1267 5.99 87.50 Cirrus ahead 08:52 1266 5.88 87.50 Approaching clouds below 08:54 1271 5.77 87.49 End leg at 2800 feet - turning back 08:55 Drop down to sample clouds on return 09:00 887 5.60 87.14 Still in clouds/haze 09:01 923 5.57 87.08 Cloud tops seem bright 09:05 926 5.44 86.87 CCN high 09:08 928 5.39 86.73 High clouds above 09:11 839 5.31 86.53 No more clouds 09:15 806 5.18 86.35 Thick clouds above 09:19 807 5.05 86.18 One half hour more at this level 09:22 790 4.99 86.04 Winds coming from the south? 09:28 832 4.83 85.73 Dry and wet scattering coefficients are decreasing during the last 15 minutes 09:30 835 4.77 85.67 Mostly clear above 09:40 832 4.44 85.24 Bright clouds - mostly clear above 09:44 877 4.25 84.97 Climb to middle of clouds 09:51 904 4.05 84.69 Ready to climb up 09:53 900 3.98 84.59 Climbing to cruise altitude 09:55 1637 3.90 84.53 Scattering and CN increasing 09:58 WINDS display is frozen 10:05 Turning to the west from southwest 10:10 Level at 18000 feet 10:13 Reboot data system 10:15 5536 3.69 83.25 WINDS is back 10:18 5533 3.72 83.10 Heading toward Male' 10:25 5533 3.79 82.60 10:40 5534 3.83 81.49 Winds are shifting from the northeast to east 10:47 5532 3.84 80.91 Winds are now coming from the southeast 10:48 5532 3.83 80.80 Clear below and a little hazy (looks clean) 11:00 5536 3.76 79.94 11:02 5530 3.75 79.80 Altostratus just above us 11:15 5535 3.73 78.81 Top of haze approximately 3.0 km 11:22 5532 3.76 78.28 Winds are coming from the northeast 11:32 5532 3.86 77.59 Winds are coming from the north 11:33 5532 3.87 77.37 Starting descent; clear above 11:37 4000 3.75 77.27 Scattering coefficients are zero 11:38 3600 Scattering is slowly increasing 11:39 Aerosol layer top at approximately 3.4 km 11:41 2700 3.53 77.10 Visibility is low 11:42 Peak in scattering is at 8500 feet 11:45 1800 Below scattering layer? Into clear air 11:52 600 3.06 76.66 Layer is still clean 11:55 63 2.90 76.57 Start 100 foot leg for 20 minutes 11:58 Mostly clear above 12:05 67 2.41 76.31 Hot CN decreased a little bit 12:15 67 1.96 75.97 End 100 foot leg climb to 8000 feet 12:23 2443 1.86 75.71 Start leg at 8000 feet (this layer is clean now!) 12:29 2446 2.09 75.48 Can see the haze layer to the right and ahead 12:34 2453 2.33 75.19 Scattering coefficients are starting to increase 12:38 2457 2.50 75.02 Scattering is increasing more 12:42 2460 2.69 74.85 Winds are now from the northeast as pollution increases 12:45 2457 2.81 74.74 Still clear above 12:53 2459 3.24 74.33 Another increase in scattering and CN 13:00 2458 3.56 74.04 Done with 8000 foot leg; Heading to Male' 13:05 1500 3.73 73.81 Descending 13:06 1400 Scattering decrease at 1.4 km 13:17 Land at Hulule'; END OF INDOEX