Michael Biggerstaff, Aircraft Mission Coordinator (TRMM OPS)
Tony Grainger, Citation Chief Scientist
Michael Goodman, DC-8 Chief Scientist
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Aircraft Mission Coordinator Summary
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Mission Summary for 8 September 1999 UTC, 9 September local
This is the only mission flown this day.
All times below are UTC
Dual aircraft mission: DC-8 and Citation
DC-8 t/o ~2025, landed ~2300 (not exact)
Citation t/o ~1956, landed ~2240 (not exact)
TRMM OVERPASS: TMI coverage everywhere in quantitative radar range, PR
coverage to NE. TMI coverage was sampled.
This event turned out like most other TRMM overpasses in which there was a chance to gather data in the PR swath. Convection that formed did so well away from the target area and even then moved and evolved quickly. At the time of launch, several strong cells had formed a broken line pattern about 220-220 km south-southeast of Kwajalein. Eighty miles from the storms, the Citation reported that their on-board radar was painting the echo at the highest level of intensity. Rather than target the most intense cell in the group, the Citation was directed to a set of three moderately strong storms at the eastern end of the line. These cells were close to the 150 km quantitative range of the radar and were moving toward the radar.
The Citation made 7 passes through these cells starting at 12K ft then 14,16,18,21, and 24 K ft. The DC-8 joined the Citation during the 6th pass and reported only moderate rain seen by ARMAR during their bow-tie over the cell location. It was evident that this cell had already completed its lifecycle. A new target was growing about 10 miles south of this cell so the aircraft were directed toward it. Two to three passes were made through this cell. However, the time of the TRMM overpass was approaching and already it appeared that little would be left of the new target by the overpass period. Virtually every cell in the vicinity was dissipating. Nothing was within 150 km range of Kwajalein.
A new cell had formed about 30 miles to the east of the cell being sampled and the aricraft were hurriedly directed to it in time for the overpass. Luckily this cell lived long enough to be sampled by both aircraft and the TMI swath of the TRMM satellite. Both the Citation (at 18K ft) and the DC-8 made 3 passes with a direct hit coincident with the satellite overflight. AMPR data indcated a nearly circular rain cell of moderate intensity with a moderately strong ice scattering signature. Since this was a rather isolated cell, it should serve as an excellent example for beam filling studies.
The DC-8 departed the area to conduct a scanning HIS experiment flying over, through, and under cirrus clouds. This was conducted about 150nm from Kwajalein. The Citation worked another cell that had formed in the quantitative radar coverage of the KMR radar. Six passes were made through this cell from 15K to 20K ft at 1000 ft increments. After that cell dissipated, no new convection was evident within 200 km of Kwajalein and the aircraft returned to base.
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Citation Chief Scientist Summary
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Mission Summary for the Second Citation Flight of 9/08/99:
The Citation took off at 1956 UTC for a satellite overpass mission coordinated with the DC8. At the time, the only targets were on the edge of the project area and beyond to the southeast. The Citation flew legs initially at 12, 13, and 14 thousand ft, skirting the edge of the high reflectivities. The Citation occasionally encountered heavy rain on these lower passes. The aircraft then flew passes through the cores of the cells from 18,000 ft to 24,000 ft in 3,000 ft intervals. Large aggregates (up to 0.5 cm) and graupel were observed in some of the passes at higher altitudes.
A new cell was identified to the south of the older ones and passes were made through this cell at 25,000 and 30,000 ft (near cloud top) with a plan to start stepping down through the cell.
At 27,000 ft, a new cell was identified for the overpass and the Citation broke off the 27,000 ft pass to head for the new cell. The aircraft descended to 18,000 ft and made two passes through that cell at 18,000 ft and two more at 15,000 ft between 2133 and 2144 UTC.
The aircraft was then directed to the only remaining target in the project area, which was visibly suppressed at this time. This cloud was penetrated at 15, 16, 17, 18, 19, and 20,000 ft. The tops of the turrets were entraining dry air and pinching off from the base before growing to a significant height. There were occasionally good updrafts and several mm diameter graupel observed, but the trend of this system was definitely toward decay.
There being no other activity in the area, the Citation returned to base. It landed at 2241 UTC for a total mission time of 2.8 hours.
Data Quality:
The data was generally good during the mission, but some degradation of the quality of the CPI images was noted. It is thought that this may be due to flying in heavy rain early in the mission, which may cause streaking of the windows. Starting the profiles higher in the cloud early in the mission may alleviate this problem.
Flight Scientist: Grainger
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DC-8 Chief Scientist Summary
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