INDOEX C-130: FLIGHT 16, 21 March 1999 Objective: Indirect Forcing and Cloud Closure Flight Mission Scientists: B. Bush and V. Ramanathan The initial mission plan of flying east of Sri Lanka was aborted due to altitude restrictions in the local air space. This alternate mission of sampling low-level clouds in a polluted area north and northwest of the Maldives was completed. Take-off from Male was at 03:55 UTC. Low-level stratocumulus were sampled at cloud level during the out-bound leg of the mission heading toward [11N,73.5E]. When conditions cleared, a slow ascent to 12,000 ft was made to characterize the haze layer. The results of this scan indicated multiple layers with the top layer at or above 3.8 km. After turning toward [12.5N,72.5E] and dropping sondes at 10 and 11 N, the C-130 flew through altostratus before starting a descent to the boundary layer for sampling of lower-level clouds. No low-level clouds were present, so the C-130 flew at 2,000 feet toward [10N,68E] to another cloud field. The low-level stratocumulus were encountered at approximately [11N,71E] at 800 meters. The cloud field was relatively dense compared to other INDOEX missions. Four 20-minute level-flight legs at cloud level, 100 feet, 6,000 feet, and 17,000 feet were made along a single track. These clouds were embedded in a haze layer (with multiple layers) that had a top of approximately 3.7 km. The in-bound trip consisted of a high-level (17,000 feet) with dropsondes at approximately 10, 8, and 6 N and a pass over KCO and Male' with coordinated dropsondes at each location. A final slow descent from Male' back to KCO with a final 20-minute leg past KCO at 100 feet completed the mission, landing at Hulule' airport at 12:52 UTC. The aircraft data system went down twice and had to be rebooted one time. Minimal amounts of data were lost during these interruptions. Also note that the CN was configured to sample cabin air during this flight. The following is a chronology of the mission: UTC Alt Lat Lon Comments ------------------------------------------------------------------------------ 03:55 4.18 73.53 Take off and climb to cloud altitude Heading to [11N,73.5E] 03:59 747 4.11 73.5 In clouds (stratocumulus) 04:02 725 4.58 73.5 No apparent cirrus above Left wing LWC not functioning 04:10 732 5.04 73.48 No clouds ahead but very hazy 04:13 Light cirrus or thick haze above - indistinguishable at this level 04:15 666 5.3 73.5 Entering clouds again 04:18 664 5.45 73.5 Mostly clear and hazy 04:23 663 5.75 73.5 Scattering coefficient increasing 04:26 662 5.9 73.5 No distinct top of the haze layer (1.5-2 km range There are multiple thin haze layers above. The density increases above 1 km 04:27 CN increased over last 15 minutes 04:27 664 6.02 73.5 Entering clouds 04:30 714 6.13 73.5 Large band of stratocumulus ahead appear to be thick Possibility of being thick enough for nearly isotropic diffuse radiation signal 04:33 771 6.37 73.5 Still in stratocumulus - highest peak just below 2.5 km Most peaks below 2.0 km; some much lower 04:38 690 6.59 73.5 Turning a little to follow the clouds CN count is increasing; scattering not increasing (small particles?) No 10 nm particles (more between 30-100 nm) 04:43 711 6.83 73.4 Still in clouds - very hazy between clouds 04:44 698 6.90 73.4 Clearing a little 04:48 694 7.09 73.4 Entering thicker clouds 04:51 697 7.31 73.5 Still in clouds, but visibility is low 04:52 697 7.43 73.5 Haze is increasing making it hard to see clouds ahead 04:58 736 7.69 73.4 Scattering coefficient is decreasing; CN going down 04:59 749 7.72 73.4 Rh = 95% (cause of "thick" haze?) 05:02 787 7.93 73.4 Few clouds ahead but still very hazy 05:04 788 8.02 73.4 Scattering coefficient starting to increase (Same gradient predicted by NCAR AEROD product) 05:06 784 8.10 73.4 Brown haze visible on horizon 05:11 770 8.4 73.4 Clear ahead; decide to profile through haze layer 05:14 1140 8.57 73.4 Still climbing 05:16 1536 8.70 73.48 Top of one layer is approx. 2.0 km 05:17 1809 8.8 73.5 Still hazy above - still more layer(s) above 05:20 2100 8.91 73.48 Absorption is low (functioning?) Top of layer above is approximately 3.8 km 05:24 2800 9.16 73.48 Thin cirrus or haze visible above 05:25 2950 9.26 73.48 Sharp increase in the scattering coefficient 05:27 3100 9.33 73.48 Thin cirrus or haze visible above 05:31 3788 9.60 73.47 Top of haze layer? Starting level flight 05:33 3777 9.72 73.4 Hazy above; some sparse clouds below 05:36 3778 10.0 73.47 Dropsonde #1 05:42 3774 10.38 73.46 High scattering layer last 5-10 minutes Probably not above aerosol layer at this altitude 05:53 3776 10.98 73.3 Dropsonde #2 05:54 Turning toward [12.5N,72.5E] - same altitude Heading toward region of dense clouds in high aerosol 05:56 3773 11.13 73.2 Some low clouds in haze layer below 05:58 WINDS display is periodically out 05:59 3773 11.33 73.0 Some cirrus or possibly altostratus ahead 06:05 WINDS display is frozen 06:06 3773 11.76 72.8 Thick clouds overhead 06:15 3777 12.28 72.5 In altostratus clouds (3 degrees C) 06:17 Starting descent to sample low level clouds 06:20 WINDS is out - ejecting tapes 06:22 3000 Hold descent until WINDS is functional 06:25 12.36 72.45 Hard reboot of system 06:37 Starting to record data 06:38 3100 12.4 72.4 Restart descent to cloud layer (if it exists) No low level clouds are apparent below 06:50 1100 12.35 72.36 "Clean" layer found during descent 06:55 Still spiraling down 06:56 Level at 100ft - head toward [12N,71E] 06:57 Climbing to 2000ft 07:02 Hazy - can see clouds in the distance Some tops are above the haze layer? 07:12 608 11.84 71.5 Hazy - humidity is increasing, visibility is decreasing 07:18 604 11.87 71.2 Same conditions - hazy with little visibility (Rh = 84%) 07:21 606 11.88 71.06 Some high clouds above (altostratus again?) 07:23 600 11.88 70.94 Turning to [10N,68E] to sample low clouds 07:25 600 11.81 70.85 07:28 617 11.70 70.72 Clear but hazy above; no visible clouds ahead 07:30 Turn of MASP probe (cause of WINDS problem?) 07:33 611 11.53 70.47 Still no visible clouds ahead but visibility is poor 07:42 611 11.21 69.95 Can finally see clouds ahead! 07:45 763 11.14 69.84 Nearing cloud layer; climbed slightly to cloud level (Rh dropped) 07:47 860 11.08 69.76 Entering clouds 07:48 Descending 50 ft 07:52 797 10.91 69.48 Very dirty clouds - CCN is high 07:59 797 10.68 69.09 Some white cloud tops above the haze layer 08:03 797 10.55 68.88 Cloud field is relatively dense (intercloud spacing is small) 08:07 797 10.41 68.68 8 more minutes (minimum) requested at cloud level 08:13 795 10.24 68.40 Still in dense cloud layer (CN dropping) Is XBABS working? 08:19 797 10.02 68.13 5 more minutes until descent to 100ft 08:25 9.81 67.83 Descending to 100ft and reversing course Hazy above - no apparent cirrus 08:28 65 9.79 67.83 Start 20 minute leg at 100 ft 08:36 72 10.03 68.19 Rh = 74% 08:42 68 10.23 68.47 08:48 10.42 68.74 End 100 ft leg - climb to 6000 ft (above cloud top and within haze layer) 08:53 1500 Passed through a very dry layer 08:55 1878 10.37 68.63 Heading back to [10N,68E] for 20 minutes at 6000 ft; above cloud albedo run within haze layer Top of haze layer approximately 3km (hard to define) 08:58 1865 10.27 68.50 Still in aerosol layer 09:03 1872 10.10 68.25 Layer exists from 3.1 to 3.7 km 09:06 Cloud tops appear bright 09:10 1870 9.85 67.88 Hazy with no cirrus above 09:13 1868 9.74 67.72 Clouds below have much haze between them; can still see the ocean's surface 09:15 9.65 67.59 Done with 6000 ft leg; climb to 17000 ft for above cloud and haze albedo measurement 09:18 Scattering coefficient has peaks and dips during ascent 09:23 3631 9.63 67.55 Above haze (as predicted by SABL) 09:26 Still climbing; light cirrus above 09:27 Missed CERES-TRMM over pass 09:29 4686 9.59 67.60 Scattering is zero 09:33 Begin level flight at 17000 ft 09:35 WINDS is down last few minutes 09:37 5205 9.75 67.79 Dropsonde #3 09:41 5199 10.19 68.13 Clouds below within haze 09:49 5199 10.39 68.47 Light cirrus above 10:05 5200 11.23 69.33 End 17000 ft leg at this heading; turn toward KCO 10:08 5201 11.05 69.46 Too much cirrus for MCR maneuver Cloud cover below varies - few low cloud now 10:20 5204 10.12 69.82 Thin cirrus above; scattered low clouds below in haze 10:23 5204 9.92 69.90 Rh increasing slightly 10:26 5198 9.72 69.97 Flying over stratocumulus 10:36 5199 9.00 70.27 10:43 5204 8.52 70.48 Still over stratocumulus 10:49 5202 8.00 70.69 Dropsonde #4 10:55 5206 7.55 70.86 Approaching some cirrus; stratocumulus below in haze 10:57 Turning a little toward KCO; in dry layer 11:04 5211 6.99 71.32 Clearing below; still hazy 11:08 5206 6.83 71.50 A little cirrus above - turning SABL upward 11:10 SABL doesn't see cirrus up to 15km 11:12 5204 6.60 71.75 Stratocumulus getting denser below and ahead 11:16 5199 6.37 71.98 Haze is thinner below but top is still approximately 3 km. Stratocumulus at approximately 1.0 km in haze 11:22 5209 6.01 72.33 Dropsonde #5 11:26 5207 5.80 72.55 Thinning stratus below 11:33 5208 5.40 72.99 Moderate stratus below 11:42 5207 4.96 73.47 Dropsonde #6 (over KCO - coordinated with upsonde) 11:42 Turning toward Male' (maintain same flight level) 11:47 5204 4.60 73.50 Approaching cirrus ahead 11:52 5207 4.18 73.52 Dropsonde #7 (over Male' - coordinated with upsonde) 11:53 Turning back toward KCO; descending slowly to reach 100 ft 50 km past KCO 11:58 3800 4.38 73.52 Descending 12:00 3349 4.53 73.49 Scattering starting to increase 12:03 2761 4.7 73.47 Scattering and CN increasing 12:08 Aerosol layer approximately 2.0 - 3.0 km 12:12 960 5.29 73.50 Still descending 12:14 856 5.33 73.51 Entering clouds; hazy between cloud Liquid water content is increasing 12:20 WINDS frozen 12:21 Level at 100 m going North 12:22 Turning and descending to 100 ft 12:24 Starting 20 minute 100 ft leg past KCO 12:28 88 5.42 73.49 Under clouds 12:34 Winds appear to come from the NW so change course to pass KCO on downwind side (East) 12:36 86 Past KCO - saw smoke from fires near harbor CN increased from KCO plumes 12:41 86 4.58 73.46 Climbing to 2000 ft on approach to land at Male' 12:52 Land at Hulule Airport