This was planned as a 3-aircraft mission, but after the DC8 and

Convair got in the air, the Citation called TRMM Ops with a radio

problem that they worked on for a while but eventually caused them to

cancel. The Convair had a pressurization problem that kept then

at/below 10Kft. For this mission, the Kwaj radar and the ship radar

were both operating on the 10 km scan cycle for better vertical

resolution. The small sacrifice of high altitude coverage between

25-35 km radius was deemed acceptable, as most of the mission was at

longer ranges from both radars.

Within the altitude constraints, this mission was successful in

obtaining a period of coordinated legs in a mesoscale convective system

beginning in the late mature stage evolving into mostly stratiform

echo. The system was associated with a low level wave and extended

over 150 km at the beginning of the flight, breaking into smaller blobs

with time. The first flight leg by the DC8 (7 52' 167 41' to 7 44' 166

51') apparently encountered some moderate turbulence near some of the

stronger cells. The Convair intercepted this leg behind the DC-8, so

we simply allowed the DC-8 to catch up to the Convair with time. The

position of the leg was adjusted northward at 0355 to stay with the

system. We switched to a shorter leg (#3) in a bowtie pattern for the

DC-8 on which both aircraft hit the center point at 0454 and 0455, then

kept repeating for an additional hour as the system weakened. From

0530-0555, the Convair continued on the line while the DC-8 stepped

down from FL 410 to 350 to 300 to 250. In summary, this system was

covered by both aircraft from ~0350-0555.

The last hour of the mission focused on a group of smaller cells in

the east dual-Doppler lobe. The DC-8 made two passes, line 4 across

the cells and line 5 along their SE-NW orientation from ~0605-0625.

The Convair was only able to get on the line from NW-SE at about the

time the DC-8 departed, then made one more pass back to the NW before

landing. Apparently there were some small but fairly strong cells, as

the AMPR reported some ice scattering down to 180K.

_____________________________________________________________________________

_______________________________________________________________________

A coordinated mission was flown with the University of Washington

Convair. The DC-8 was in the air at 0335 UTC which was roughly 5

minutes late because the DADS system, which archives the navigation

information, was having trouble coming up. The DC-8 began by climbing

to 35,000 feet to set up on a line between 7 degrees, 52 minutes North

latitude, 167 degrees, 41 minutes East longitude and 7 degrees, 44

minutes, 166 degrees, 50 minutes East longitude. This line was only

flown once, but probably contained the most significant rain and ice

signatures of the day based on ARMAR and AMPR observations. The 85 GHz

brightness temperature depression within the storm system located at

7.12 degrees North latitude, 166.03 degrees East longitude approached

171 Kelvin which was the coldest ice signature observed during the rest

of the flight. The Scanning HIS also reported seeing cloud top

temperatures of 253 Kelvin at the center point of this line.

Three runs were made of Line 2 which had coordinates of 7 degrees,

45 minutes North latitude, 166 degrees, 51 minutes East longitude and 6

degrees, 8 minutes East latitude, 167 degrees, 28 minutes North

longitude. The DC-8 experienced some turbulence on this line and

climbed to 40,000 feet. The CPI and CPP both sampled ice particles

during the first run of this line. Despite the turbulence experienced

during the first run of this line, the convection decayed quickly

between the second and third run of this line.

At 0452 UTC, the DC-8 began Line 3 which became a bowtie pattern

after the first run. The ARMAR reported 30 - 40 dBZ observations with

rain signatures up to 1 - 2 kilometers and possible ice signatures at 5

- 6 kilometers altitude at 0503 UTC when the DC-8 was passing in the

vicinity of 7 degrees, 55 minutes North latitude and 166 degrees, 52

minutes East longitude. The Scanning HIS also observed cloud top

temperatures of 225 Kelvin during this time. The TRMM Operation Center

decided the convective system had turned to stratiform rain by 0532 UTC

and requested that the DC-8 descend to 25,000 feet to sample the

microphysical particles. The DC-8 continued the bowtie pattern but

descended 5,000 feet during each turn. The CPI and the CPP reported ice

particle sizes between 100 to 200 microns throughout the descent until

25,000 feet was reached. At this altitude, a much broader spectrum of

particles with sizes up to 800 microns were sampled.

After finishing the bowtie pattern, the DC-8 and Convair were

directed to the Eastern Dual Doppler region in the general vicinity of 8

degrees, 30 minutes North latitude and 168 degrees, 1 minute East

longitude to sample small convective cells. The DC-8 climbed to 35,000

feet for this sampling period. At 0611 UTC, the ARMAR reported seeing

rain signals up to 4 kilometers while the Scanning HIS observed cloud

top temperatures at 265 Kelvin. The DC-8 began a return to Kwajalein at

0633 UTC and landed about 20 minutes later.

Overall, the DC-8 instruments performed as expected. The ARMAR

experienced two crashes that were corrected quickly. The AMPR also

experienced some jittering during data collection due to turbulence of

the aircraft. Both of these problems are very small and should not

seriously affect the data quality from either instrument. A total of 3.4

flight hours were used during this mission leaving 96.6 hours left for

research use.

UNIVERSITY OF WASHINGTON FLIGHT FOR KWAJEX

DATE: 3 August 1999

UW FLIGHT : 1788

Goals of Flight: Coord. Flt with DC-8 , Citation and CV-580 beneath TRMM sat

Accompishments : Coord flight of CV-580 and DC-8 in six prescib. precip bands. No precip beneath TRMM sat.

Period of flight: 1540-1912

KWAJEX hours remaining: 74.14

Peter Hobbs

Univ. of Wash.

4 Aug 1999