INDOEX C-130: FLIGHT 10, March 9, 1999 Objective: Clear Sky Radiation Gradient Mission Mission Scientists: T. Clarke and A. Bucholtz Summary: This 8hr 46min mission was a successful clear-sky radiation-gradient flight. The primary purpose was to measure the forcing as a function of optical depth along a gradient in the pollution plume coming off the Indian sub-continent. Meteorological conditions set-up a situation where mostly clear skies (including no cirrus) prevailed in the vicinity of Male from the Equator to 10N. In addition, the pollution plume was pushed south with a maximum near the tip of India, while cleaner skies prevailed to the south-east of Male. We initially flew at high altitude to the cleaner, clear sky region near the Equator and 75E. Here we flew a clear-air closure stack. We then retraced our track back to the northeast flying at 100 ft. We continued past Male flying at 100 ft all the way to 9N 72.4E measuring the optical depth, microphysical, and chemical properties all along the gradient. Mostly clear skies prevailed along this leg. We also twice profiled up to 8000 ft and then immediately back down to 100 ft approximately 1/3 and 2/3 of the way along this lower leg. At the far northern end we attempted to perform a 2nd clear-air closure stack. This stack contained clouds, but there should be enough clear sky portions to obtain the closure data. We then retraced our track back to Male, flying at high altitude. Near KCO we descended to 100 ft and performed a 20 min fly-by centered on KCO. UTC 03:28 Taxi 03:34 Take-Off; clear sky above, small cirrus to far east 03:37 Turn to E then SE; Bsp approx. 30e-6 m-1 (winds NE) 03:41 Pollution layer at approx.5000 ft; Bsp approx 80e-6 m-1 (wind NW) 03:43 Scattering higher aloft than @ surface 03:44 (4.04N 73.8E) Bsp dropping quickly at 6400 ft to clean air; mostly clear above with some widely scattered Ci ahead; clear below 03:51 Volatile CN near 11500 ft; wind from NW, approx 5m/s; Bsp approx 0 03:53 (3.5N 73.5E) Some small, thin Ci wisps ahead; very clear below, just a bit hazy 03:54 (3.4N 73.8E) Turn to SE 04:03 (2.8N 73.9E) Some small Cu below 04:06 (2.72N 74.15E) Clear above with some very scattered Ci ahead; very scattered stratocumulus below; lidar reports seeing haze layer top approx 2200 m 04:12 Clear above, Ci cloud streak ahead; very scattered stratocu below 04:20 (18000 ft; 1.87N 74.6E) Ci streak overhead leading off to E; passing over scattered stratocu cloud street; lidar reports 2 weak layers below at approx 3.5 km and 2.2 km 04:23 Delay MCR turn - some Ci above; Did CO die? 04:25 (1.5N 74.7E) Clear above; Ci streak behind to E; clear below; we are in between 2 widely-spaced cloud streets 04:28 Some big Cu on SW horizon - all instruments are volatile; wind from S (ITCZ) 04:32 (1.1N 75E) Clear above; passing over 2nd scattered stratocu cloud street below 04:38 (0.732N 75.15E) Clear above; clear below 04:40 (18000 ft; 0.57N 75.2E) start MCR turns in clear region between clouds; clear above and below (some small Cu) 04:43 MCR turn (9:45 LST); Cu at edge of clear; #27 and #28 Digital pictures 04:55 Hit our own exhaust during MCR maneuver 04:56 End MCR turn; clear above and below 04:59 Lidar reports not seeing any haze layer 05:01 (18000 ft; 0.448N 75.3E; 100 deg heading) Start 20 min leg; clear above, come Ci off to NE; clear below; some widely scattered, small Cu below, but soon flew out from over them; winds SE @ approx 4 m/s 05:09 (0.37N 75.8E) Turning to do an L-shaped pattern to stay in clear area; clear above, no Ci 05:11 (heading S) Clear above and below; convective Cu on horizon ahead to S 05:19 Just starting to get over stratocu 05:20 (0.492S 75.702E) End leg 05:21 (0.502S 75.704E) Turn to N and start descent profile to mid-point of L; clear above and below 05:28 (14000 ft) Wind change to NE from SE 05:32 Lidar reports top of marine boundary layer at 1 km 05:34 (7500 ft and descending) Starting to hit haze layer; can visually see raised haze layer on horizon; thin haze above cloud; #29 digital picture 05:36 Lidar looking up now 05:37 Turn and descend to W at 500 ft/min; clear above and below 05:40 (Approx 4000 ft and descending) Entering lower haze layer; clear above and below 05:42 Haze layer at 5000 ft with max near 3000 ft; cloud top (few near 2400 ft ahead) 05:44 (1500 ft and descending) Wind WNW at 4 m/s; some small Cu; Bsp down to approx 33 near cloud level, increases to approx 50 near surface 05:47 (100 ft) Turning to reverse course 05:50 (100 ft) Start leg (1st part of L); clear above 05:57 (100 ft) Clear above; neph impactor approx 15% in coarse; 75 km variability in Bsp again; lidar reports increase in layer thickness too. 05:58 (0.384N 75.8E) Axis of L-pattern; turning to head south over other leg 06:05 Clear above 06:12 End leg; Turning, just at edge of clouds 06:13 Climb to 3000 ft; cloud base at 600 m, cloud top at 700 m 06:16 (Level at 3000 ft) Start 20 min leg; hazy out; clear above and below; cirrus off to far east; DMA problems 06:20 1 or 2 small cumulus at our level off to our sides 06:25 Less variation in this atitude - near cloud top 06:28 Turn to west; wind from SW @ 4 m/s; clear above and below 06:36 Clear above and below (but hazy) 06:39 Aerosol dropping to west 06:41 End leg; spiralling up 06:45 (Reached 8000 ft) Out of upper haze layer @ 2300 m 06:47 Descending to 100 ft 06:48 Cloud top @ 900 m; Cloud base @ 700 m 06:49 Descending through cumulus field 06:53 (Level @ 100 ft) Mostly clear above with some very scatt small cumulus 06:54 (0.86N 74.9E) Scatt coef approx 39e-6 m-1, absorp. coeff approx 23e-6 m-1, CO approx 2ppb, O3 approx 29ppbv, CN approx 1300 counts 07:00 Some thin cirrus streaks off to our right (to east), some just ahead 07:05 (1.47N 74.8E) Call to Ops Center: they suggest going to 9N 74.5E; there's a cloud bank south of Trivindrum @ approx 7N; they suggest doing E-W legs, more clear sky to west 07:13 Aerosol starts increasing (CN stable,Bsp oscillation) from approx 30e-6m-1 to approx 50e-6m-1 07:24 (2.44N 74.3E) Clear above; scatt coeff approx 50e-6m-1, abs. coeff approx 20e-6m-1, CO approx 2.0ppb, O3 approx 36ppbv,CN approx 1700 counts 07:29 (100 ft; 2.74N 74.15E) Lidar report: 3 layers above: boundary layer, 1.0-1.3 km, 1.3-?km, with 100 m space between each layer 07:32 (100 ft, 2.88N 74.09E) Lidar reports mid-layer merging with lower boundary layer 07:38 (100 ft, 3.14N 73.97E) Scatt coeff approx 50e-6m-1, abs coeff approx 20e-6m-1, CO approx 1.5ppb, O3 approx 40 ppbv, CN approx 2000 counts 07:41 (3.32N 73.9E) Scatt small cumulus above 07:44 Island off to our left 07:47 (3.62N 73.74E) Lidar report: boundary layer and other 2 layers have all merged and deepening 07:48 Climbing to 8000 ft; scattered cumulus around; Bsp approx 40e-6m-1 @ surface; layer increasing @ 1000 m (3000 ft) to Bsp approx 80e-6m-1; second layer @ 1600 m, Bsp approx 9e-6m-1 07:50 1st haze layer from approx 1-1.4 km, peak approx 1300m, 2nd haze layer from 1.5-2.25 km, peak approx 1600 m 07:54 (Reached 8000 ft, starting descent) Clear above; very small scattered cumulus below; upper layer was much stronger 07:59 Descending through patch of cumulus clouds, (abs coeff much higher on descent); high (anomalous?) absorption; wind shear 08:02 (100 ft and level) Start leg; scattered, small cumulus above; Bsp approx 25e-6m-1 but increasing fast away from clouds; CN steady 08:04 (4.6N 73.74E) Abs coeff approx 22e-6m-1, CO approx 1ppb, O3 approx 40ppbv,CN approx 2000 counts 08:10 Lidar showing increase; density, nephelometer, and absorption - strong gradient, but small cumulus above @ 1 km; hard to see in thick haze; O3 steadily dropping 08:18 Pilots report approx 4 hrs possible time remaining due to fuel constraints 08:26 (100 ft, 5.83N 73.38E) Passing some beautiful islands; scattered cumulus above; Bsp approx 75e-6m-1, Babs approx 15e-6m-1, CO approx 1.5ppb, O3 approx 26.5 ppbv; CN approx 1900 counts 08:34 Carbon absorption highly variable compared to most data 08:37 (100 ft; 6.45N 73.2E) More dense scattered cumulus above 08:41 (100 ft, 6.7N 73.14E) Passing more islands; scattered cumulus above; CN rising 08:44 Clear above 08:47 (6.98N 73.56E) Climbing to 8000 ft; passing through field of cumulus 08:49 Clouds @ 2500-3000 ft; absorption spikes in clouds 08:51 Got above clouds @ 5200 ft 08:53 (7.35N 72.96E) Clear above; Deep haze layer; absorption looks bad - too high loading?; dense, scattered cumulus below 08:56 (reached 9000 ft, starting descent) clear above; looks clear ahead 09:06 (100 ft) Clear, but very hazy above 09:09 (100 ft and level) Bsp increasing; Bsp still varies with 10 min period; closure legs will be orthogonal to current heading so period should change 09:14 (100 ft; 8.52N 72.54E) Clear, but very hazy above (you can smell it!) 09:22 (100 ft) Turn to E for surface closure leg 09:23 (100 ft; 9.0N 72.44E) Start 20 min leg to east @ minimum in Bsp; clear above 09:26 Scattered cumulus above 09:29 Bsp approx 85e-6m-1, Babs approx 38e-6m-1, CO approx 1.5ppb, O3 approx 45ppbv, CN approx 2600 counts 09:31 (8.98N 72.96E) Clear above 09:33 Scattered cumulus above 09:38 (8.97N 73.32E) Scattered cumulus above 09:39 Lidar report: boundary layer approx 1km deep; can't see to higher layers 09:40 Clear above 09:43 End leg; Spiralling up to 5000 ft (through scattered cumulus) 09:47 (8.91N 73.7E) Still spiralling 09:51 (5000 ft and level) Start 20 min leg; scattered cumulus below; clear above 09:55 Clouds in closure region @ 5000 ft - some clear 09:59 (9.0N 73.0E) Scattered cumulus below, then became clear area; clear above 10:04 Clear above; scattered cumulus to clear below 10:07 Bsp following CN @ altitude; XCN screwed on data system - pegged out 10:11 (9.0N 72.21E) End leg; spiralling down to 100 ft; scattered cumulus below 10:14 Passing through cumulus clouds on descent 10:16 (100 ft; starting climb to 18000 ft; heading east) Scattered cumulus above; clouds @ 1500 ft; tops @ 2400 ft; Bsp approx 120e-6m-1 @ 1.5 km 10:22 Scattered cumulus and haze below; clear above 10:25 Digital picture of haze top from 10000 ft 10:27 (9.0N 72.93E) Scattered cumulus below; clear above 10:31 Peak in haze/pollution layer approx 6000 ft 10:32 Scattered cumulus below, embedded in haze layer 10:34 CN layer 13000-18000 ft 10:35 (18000 ft and reversing course) 10:37 (18000 ft; E-W heading) Start 20 min leg; clear above; scattered cumulus below 10:47 Clear above; scattered cumulus below 10:50 SABL went down 10:54 Getting over convective cumulus; SABL back on 10:58 (18000 ft; turning south for Male) End leg 11:08 (8.4N 72.3E) Clear above; heading into clear area below 11:13 (8.08N 72.5E) Over nice clear area; clear above (too bad we couldn't see this area for the stack) 11:23 Turning for ATC 11:27 (7.18N 73.06E) Convective cumulus streets below; clear above 11:31 (6.83N 73.19E) Start descent toward KCO; need 20 min leg to test neph. Are oscillations same @ KCO? Is rounded sawtooth reversed in direction going N-S vs earlier S-N? Thin layer above main haze still evident. Some cumulus popping out of haze @ 8000 ft. Most cloud tops @ 6000 ft and less - in haze, cloud base near 2000 ft but some small lower. 11:32 (6.74N 73.19E) Descending for run by KCO 11:40 Cloud penetrations on descent; dew pt sensor wierd, higher than temp (a lagged response problem) 11:42 Peak of haze layer @ approx 5500 ft 11:47 (@ 1100 ft and descending) Scattered cumulus above 11:49 (@ 100 ft) Start run by KCO 11:52 (5.51N 73.39E) Ground speed=212 knots, wind speed approx 4 m/s; leg along wind approx.; Bsp still oscillating - same shape sawtooth 11:55 (5.3N 73.44E) Scattered cumulus above 12:00:44 Pass abeam KCO on east side 12:04 Clear above 12:07 Convective cumulus ahead 12:08 End leg 12:20 Land