discussion810

Mission Summary for 11 August, 1999

Anthony Guillory, DC-8 Chief Scientist

Peter Hobbs, Convair 580 Chief Scientist

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11 Aug (UTC and local date). All times in UTC

DC-8 Mission Scientist Report for 11/12 August 1999 (Julian Day 223/224) UTC.

The DC-8 took off from Kwajalein at approx. 2145 UTC. The aircraft

initially set up on a SW-NE line to the east of the Kwajalein Atoll at

36,000 feet. This line was repeated 3 times, with the last two legs being

at 39,000 feet due to moderate turbulence on the first pass. ARMAR data

revealed light to moderate precipitation for the length of the line on each

repetition. Most of the observed precipitation appeared to be stratiform

with some convective precipitation on the south end and west side of the

line. AMPR also noted good precipitation in the 10 GHz channel with one of

the heaviest cells having a Tb of 278K just prior to starting the first run

of this line at 2207 UTC. The CPI began having icing problems early into

the flight and from that point on the instrument preformed intermittently.

CPP also experienced problems during this line with its 2D-C probe. No CPP

data was recorded after 2214, except for the Cloudscope.

The DC-8 then lined up on a second line (same northern endpoint as line 1,

but with the southern end shifted eastward) beginning at about 2248. This

line was repeated twice, before the aircraft began experiencing a drop in

cabin pressurization which resulted in the aircraft decending to 24,000 feet

and flying eastward to thaw out a frozen value. During the first two runs of

the line, ARMAR reported moderate stratiform precipitation and AMPR observed

one cell at 2251 with a 10 GHz Tb of 280K. The ops center reported good

bright band structure in the Kwaj radar data near the end of the second run

of this line (approx. 2306 UTC) and ARMAR confirmed that observation. The

CPP went down during this line. After thawing the valve out, the DC-8

climbed to 36,000 feet for the remainder of the flight. After returning to

altitude the aircraft repeated the second line for a third and final time.

ARMAR continued to report mostly stratiform precipitation but with some

convective cells on the southern end. AMPR showed good precipitation in the

10 GHz channel.

The third line was oriented ENE-WSW. The DC-8 began the line at 2355 and

only made one pass before the orientation was changed to a more NE-SW

orientation (line 4). The fourth line was performed six times. AMPR

reported light to moderate precipiation on the third line in isolated cells.

ARMAR continued to report seeing precipition similar to the rest of the

day's flight lines (i.e., mostly stratiform with isolated convective cells).

AMPR also observed brightness temperatures near 150-165K in the 85 GHz

channel at the southwestern end of the leg on several passes. Both the third

and fourth lines were coordinated with the UND Citation.

To summarize the instrument problems: ARMAR tape recorder is experiencing

problems reading back the data; however, they have a high level of

confidence that the data were successfully recorded. AMPR is experiencing

some problems with its new 28V power supply; however, this has only a slight

impact on data quality. CPP expericence a failure of the 2D-C probe near

2214 UTC and no data, except Cloudscope data were recorded after that. CPI

experienced intermittent problems throughout the flight and failed

completely at approx 0015 UTC.

The aircraft used a total of 4.1 flight hours during the mission leaving

86.5 hours left for research use.

Anthony R. Guillory

TRMM KWAJEX Experiment at Kwajalein Island

aguillory@guillory.kwajex.espo.nasa.gov

(805) 355-8116 (AMPR Office)

UNIVERSITY OF WASHINGTON FLIGHT FOR KWAJEX

DATE: 12 August 1999

UW FLIGHT : 1792

Goals of Flight: Coordinated flight with Convair-580, Citation and DC-8 in good mesoscale system

Accomplishments : From about 0946-1037 LT three aircraft well coordinated along line 1 in stratiform and convective regions with heavy precip. Convair aborted coordinated flight at 1037 due to less than max power from right engine

Period of flight: 0924-1108 LT

Approx: Local Time (UTC=local time minus 12 hours)	Activity
0931	Take-off
0935-0941	Below cloud bases to south of Kwajalein
0941-0946	Climb to 3, 000 ft
LINE 1 A= 08 deg 17 min/ 167 deg 52 min B = 08 deg 51 min/ 168 deg 06 min
0946-0955	Head to A and climb to 8, 000 ft
0956-1010	A to B at 8, 000 ft
1013-1024	B to A at 11, 000 ft. Some ice particles
1028-1037	A to about 2/3 way to B at 14, 000 ft (+1 deg C)
Above passes on line 1 occurred in light to heavy precip with stratiform and convective components. Strongest convection was around point A. Due to a power problem with right engine, Convair broke away from coordinated mission at 1037. It then spiraled down from 14, 000 ft to 3, 000 ft close to line 1 and in heavy precip (data should be good)

Instrument malfunctions:

1) FSSP-100 and J-W went down about 0955 LT

2) CNC-3 responds to rain

3) DMT liquid water meter responds to rain as well as cloud water

Aircraft malfunctions :

1) Radar

2) Right engine not developing full power

KWAJEX hours remaining: 64.97

Peter Hobbs

Univ. of Wash.

Citation Flight Summary for 8/11/99.

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The Citation took off at 2150 for a planned TRMM mission. The aircraft loitered at the North end of a line being flown by the Convair in order to get synchronized with its path to the South. The first pass was begun to the South at 21,000 ft and then stepped up to 24,000 ft for a pass back to the North. As we were seeing nothing but ice crystals at these altitudes, and since the Convair had to break off due to engine problems, the Citation began to step back down, making passes near the melting level. This continued for a number of passes and the final pass was made in the rain at 10,000 ft. The Citation returned to base and landed at 0154, for a total mission length of 4.1 hours.

Data Quality. All instruments appeared to be working throughout the flight. Real-time displays of winds and 2D-C and HVPS were not good, but the data appears to have been recorded correctly.

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Flight Scientist: Grainger.

Ed Zipser, Aircraft Mission Coordinator

11-12 Aug UTC, 12 Aug LT. All times below are in UTC

3-aircraft mission for Convair, Citation, and DC-8.

DC-8 t/o ~2145, land ~0140 (not exact)

Convair t/o ~2132, land ~2301 (not exact)

Citation t/o ~2155, land ~0145 (not exact)

(No TRMM overpass)

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This was the largest precipitation system sampled by aircraft in KWAJEX to date. It was a major system in its own right, and part of an even larger active region extending some distance east and especially west of Kwajalein. The night before, a system built east of Kwaj, passed over the island, and was weakening west of Kwaj at sunrise. But from ~1700-2000 (0500-0800 LT) new convective development took place over the entire eastern semicircle of our radar out to at least 150 km, loosely organizing into NNE-SSW bands, and covering a large area with precipitation by 2000 UTC. The low level winds on Kwaj were very light during the night but by 2000 UTC were from the NW at 10-15 knots, converging into the building convection area to the east.

[While the decision to launch all a/c ASAP was a 'no-brainer', we were further stimulated by a bizarre edict from the powers that be: A ceremony involving a visiting general was not to be disturbed by engine noise, so the airfield was to observe a quiet hour between 1020-1120 LT. All three KWAJEX aircraft got off the ground well ahead of the potential order to snuff engines.]

The decisions on setting flight lines were guided by three criteria. 1) Take advantage of the huge precipitation area, with convective echoes transitioning into stratiform fairly rapidly, by sampling a truly large region which was becoming quasi-uniform. 2) Concentrate on excellent time and space coordination along the flight lines, since for the first time in KWAJEX they did not have to be moved frequently. 3) Get the best possible dual-Doppler coverage. The objective of good coordination was achieved, and mostly quite close to the center of the east dual-Doppler lobes.

The Convair developed an engine problem about an hour into the flight. They did 2-3 coordinated legs at 8 and 14Kft before leaving for an early landing. The Citation flight altitudes were thereafter altered to cover the region between 14-21Kft (approx 0 to -10C).

We intentionally sacrificed the sampling of the strong convective features on this mission. As it happened, the DC8 had all the water it could handle in the stratiform regions, having to descend to lose the icing of some valves that were sticking to get cabin pressure back up. There was one decision point at about 0000 UTC, where we were considering a shift of the mission to a growing convective area in the center of the west lobe. This was a close call, but in the end we decided to stay with a sure thing and not risk losing coordination by going through or around some very strong cells near the south end of the growing convection.

Except for the period from approx. 2315-2350 when the DC8 had to leave the pattern, the two aircraft remained very well-coordinated in the east Doppler lobe. The system gradually became more stratiform and slowly weakened. It is worth noting, however, that in spite of this weakening, it was still raining lightly in Kwaj at 0430 UTC, 3 hours after the aircraft left the pattern.

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