Michael Biggerstaff, Aircraft Mission Coordinator (TRMM OPS)
Peter Hobbs, Convair 580 Chief Scientist
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 26 August 1999 UTC, 26 August local
This is the only mission of the day.
All times below are UTC
Triple aircraft mission: DC-8, Citation, and Convair
DC-8 t/o ~0326, land ~0630 (not exact)
Citation t/o ~0358, land ~0615 (not exact)
Convair t/o ~0340, land ~0715 (not exact)
TRMM OVERPASS: Excellent overpass (TMI and PR) at 0452
Forecast guidance indicated that today should be able as good as yesterday. If only we were so lucky! While numerous isolated unicell "storms" were splattered across 50% of the radar display, nothing was merging and nothing was exceeding 6 km in echo tops. All cells were moving about 20 knots toward the NNW. If not for the satellite overpass, this mission would likely have been scrubbed.
The DC-8 performed a scanning HIS experiment through cirrus during the first part of the mssion. One long leg was flown below the cirrus, one leg through the cirrus, and another leg above the cirrus. While the DC-8 performed this experiment, the Convair was directed to a region where occassionally some some radar echoes would appear-- only slightly more dense in spacing than other quadrants. They started the "small cumulus/precipitation initiation" experiment. The Citation was also directed to the same targets, though they reported that most of the ice was below their altitude base (20K ft).
As the time of TRMM overpass neared and the scanning HIS experiment was completed, the DC-8 was directed to join the other aircraft. The very next radar update showed that the cells being worked by the two micropysics aircraft had decreased intensity very rapidly. It was evident that the area would be echo free by the TRMM overpass. In an attempt to get some DC-8 data in the PR swath, the DC-8 was quickly diverted to a small line of weak cells that had just merged at 150 km range due west of Kwajalein. There was not enough time to send the microphysics aircraft to the same location.
The DC-8 performed bow-tie patterns around this small area of weak to moderate convective cells during the TRMM overpass. Apparently there was some moderately heavy rainfall sampled by the ARMR during the TRMM overpass in the PR swath. The cloud microphysics aircraft reported that a new updraft had formed on the northern side of the cells they had been working. Both aircraft sampled this developing cell doing nearly simultaneous penetrations. Indeed, this appears to have been a very successful microphysical sampling of the precipitation growth process in a typical tropical cumulionimbus. In essence, the small cumulus/precipitation initiation experiment paid off.
Since the new cell growth gave the DC-8 a reasonable target to work, that aircraft was directed toward the others and a coordinated three aircraft mission over this cell was flown for about 20 minutes. After that, the DC-8 and Citation returned to base. The Convair continued to sample the dissipating convection in this area before returning to base.
The short summary is that the DC-8 sampled moderately heavy rain in weak to moderately strong convection during the TRMM overpass in the PR swath. The microphysical aircraft sampled a typical tropical shower from precipitation initiation through dissipation. This was also underneath the PR swath of the TRMM overpass.
Michael Biggerstaff, Aircraft Mission Coordinator
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Citation Chief Scientist Summary
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Mission Summary for the Citation flight of 8/26/99:
The Citation took off at 0357 UTC and was directed to the northwest quadrant from Kwajalein. The purpose of the mission was to fly a coordinated mission with the three aircraft to coincide with a satellite overpass. After looking for some time for any convection reaching 20,000 ft (the minimum Citation altitude for the blocks for the day), a cell was spotted that was barely going through that altitude. The Citation made three passes through that cell at 20,000 ft. There appeared to be liquid drops in the cloud at a temperature of –8 deg with almost no ice initially but some ice appearing on the second and subsequent passes. At that time, it had grown and the fourth pass was made at 21,000 ft, within 1,000 ft of the top. Subsequent passes were made at 22, 23, and 24,000 ft. The last pass was close to the maximum altitude reached by the cloud. Another pass was made through the same cloud at 22,000 ft and at 20,000 ft as the system was dying out. On the last pass, the cloud at 20,000 ft was visibly disconnected from the smaller cumulus below it. After this, the Citation looked for any other clouds that were reaching an altitude of 20,000 ft, but there were none in the project area. The aircraft then returned to base, landing at 0558 for a total of 2.0 hours.
Data Quality:
The data collected appeared to be good. The exceptions were the FSSP and King liquid water, which have been down for some time. There were some problems with the CPI late in the flight, but the data during the cloud penetrations appeared to be good. There were some problems with the data system early in the flight, but these did not affect the cloud measurements.
Flight Scientist: Grainger
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Convair Chief Scientist Summary
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UNIVERSITY OF WASHINGTON FLIGHT FOR KWAJEX DATE: 26 Aug 1999 UW FLIGHT : 1796 Goals of Flight: Coordinated flight of CV-580 with Citation and DC-8 beneath sat overpass at 1652 LT. Accomplishments : Goals achieved in broken line of precipitating cumulus congestus in various stages of life cycle. Period of flight: 1535-1935 LT Approx: Local Time (UTC=local time minus 12 hours) Activity General location of study area: 09deg 04 min/167 deg 20min 1600-1746 Many penetrations of line of Cu cong at different levels up to and below 18,000 ft. (In at least two cells, CV-580 was beneath developing cell that Citation sampled above.) Downward spiral from near cloud tops to cloud base (1,500 ft). Temps warmer than normal. 1748-1901 Aerosol study below cloud base, and spiraling up to 11, 000 ft in cloud detrained air. Instrument malfunctions: KWAJEX hours remaining: 47.69 (but can provide up to 63.69 as needed) Peter Hobbs
DC-8 Chief Scientist Summary
DC-8 Science Mission Summary
Flight: 990254
Mission Scientist(s): Michael Goodman and Anthony Guillory
Primary Objective: Fly over convection simultaneously with the TRMM
overpass at 0452 UTC.
Secondary Objective: Scanning HIS infrared observations of cirrus
coordinated with cloud physics probes of the cirrus particle size.
Flight takeoff originally planned for 0300 UTC was delayed until 0330
UTC due to lack of significant convection and problems with the AMPR
data acquisition system.
The mission began with a flight to the SW quadrant of the 150 nm radar
range ring to fly cirrus legs in support of S-HIS observations through
cirrus. The DC-8 flew 4 dogbone legs through above, below and again
through the cirrus. The first 7 minute leg was oriented approximately
N to S through the cirrus beginning near 7:30 N, 167 E. The DC-8s
second leg returned along a S-N leg above the cirrus and turned around
for the third leg (N-S) below the cirrus. The final N-S leg (06:52 N,
167:09 E to 07:39N, 169:59E) ascended from 28000 ft to 38000 ft as the
DC-8 passed from below to above the cirrus deck. The S-HIS team was
very pleased with the observations. CPP observed intermittent large
particles while in the cirrus. CPI fogged briefly during the descent
from above the cirrus to below and could not observe particles at that
time. After re-ascent CPI cleared up.
Although the AMPR data acquisition system failed shortly before
takeoff, the AMPR engineering team was able to fix the data system and
the AMPR started recording at 041935 UTC, just prior to the TRMM
overflight time.
The DC-8 flew three passes along a N-S oriented bowtie pattern. The
first leg from 08:18N, 166:21E to 08:40N, 166:21E began at 0443 UTC
and ended approximately at 0456 UTC. ARMAR reported light to moderate
rainfall during the TRMM overpass. AMPR's observations concurred with
rainfall estimated at the 5mm/hr rate. The DC-8 turned around in a NW
to SE bowtie leg from 044831 - 045055 UTC. Light rain was noted at the
first half of this leg prior to the center point. The third leg flew N
to S along the same line as leg 1 from 045403 to 045735. Both ARMAR
and AMPR reported light/moderate rain at low levels.
The DC-8 was then vectored to a third location just off the northwest
corner of the Kwajalein Atoll and performed a 5 leg series of N-S
bowties over light convection from 0506 to about 0536 UTC. The
Citation and Convair flew below at 20,000 ft and 12,000 ft,
respectively. ARMAR and AMPR observed light rain as the storms were
diminishing rapidly. With the storms dying the DC-8 returned to base
landing at approximately 0606 UTC.
Michael Goodman, DC-8 Mission Scientist
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Date: 26 Aug 99 Julian Day 2238
Take Off: 0322618 UTC
Touch Down: 060554 UTC
Flight. Hrs. Remaining: 58.7 hrs
Guest Scientist: Eric Smith
AMPR Scientist: Pete Conway
ARMAR Scientist: Bill Wilson
CPI Scientist: Paul Willis
CPP Scientist: Dan Wermers
SHIS Scientist: Dan LaPorte