Mission Summary for 22 August, 1999

Mike Biggerstaff, Aircraft Coordinator (TRMM OPS)

Anthony Guillory, DC-8 Chief Scientist

Anthony Tony Grainger, Citation Chief Scientist

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22 Aug UTC. All times below are in UTC

2-aircraft mission for Citation and DC-8.

DC-8 t/o 1857, land 2117

Citation t/o 1918, land 2226

NO TRMM OVERPASS

A tropical wave disturbance at lower levels and a weak short wave led to a region of deep convection in the area. Most of the activity was to the southwest but a few clusters of multicell storms remained within the KWAJEX operational zone. The convection was moving at approximately 20 knots just slightly north of due west. At the time the aircraft took off, the deepest cells were just crossing into the Roi Namur no-fly zone. Other cells, with tops around 12 km and peak reflectivity near 40 dBZ existed to the west-southwest. The aircraft was directed to this region.

By the time the DC-8 got to altitude (37K ft), the convective cells had weakened and nearly dissipated. The first bow tie pattern was flown in the vicinity of the dissipating precipitation before the Citation could get on station. The cloud physics station on the DC-8 reported some large particles in the dissipating precipitation and ARMR reported moderate rain. The flight line was moved quickly to the west, to just about the 150 km range of the radar display. The Citation joined the action and sampled several of the convective cells within this region. They started at 15K ft altitude and increased altitude in 3000 ft steps.

During the 4-5 passes over these convective cells the DC-8 remained at 37K ft but reported several large particles being sampled by the cloud physics probe. The Citation flew through several of the dissipating cells and also sampled an intense (tropical standards) cell at the southern end of the line. They reported a strong updraft and graupel which unfortunately knocked out the last hot wire liquid water probe. The coldest 85 GHz brightness temperatures recorded to date (131 K) were found in this cell. The DC-8 encountered moderate turbulence and deviated as necessary around some of heaviest precipitation.

As this line moved beyond the range of quantitative radar coverage, a new line was set up to sample some of the remaining convection that had passed to the west of Roi Namur. Three passes were made down this line with the Citation joining the new line by the second pass. Moderate to heavy rain was sampled on each pass. After this line moved to the west of the radar coverage, the DC-8 returned to base. The Citation continued working some of the convective cells beyond the 150 km range of the Kwajalein radar. Eventually those cells dissipated and the Citation flew a surveillance pattern around the remaining echo. They then climbed to 37K feet and performed a spiral descent through weak anvil. No reflectivity could be detected with the Kwajalein radar. After descending to roughly 21500 feet at a rate of about 250 feet/min the Citation reported being out of cloud and returned to base to prepare for the afternoon mission.

In general, this mission contained numerous passes through strong or moderately strong tropical convection with little or no stratiform rain. The coldest 85 GHz brightness temperatures (131 K) were recorded on this flight and the DC-8 cloud physics probe sampled "monster aggregrates" according to those on-board.

DC-8 Chief Scientist Summary

The DC-8 took off at 1857 UTC on a joint mission with the UND Citation over multicellular convection over the NW Quadrant of of the Kwaj radar.

On climb out (~1808), CPP reported very large aggregate particles. After leveling off, the DC-8 set up on a bowtie pattern which was oriented SSW - NNE initially. ARMAR reported moderate rain near the beginning of the first line and decreasing along the line. On the second leg of the bowtie, not much precipitation was observed. ARMAR only noted some precipitation aloft. The CPI and CPP instrumentation noted good particles sizes, etc. at the beginning to middle of the line.

The next line was oriented SW-NE and to the NW of the previous line. During the run, ARMAR observed precip aloft near the middle of the line and heavy rain near the end. The AMPR observations are similar, but also depict a good ice signature in the 85 GHz channel on the north end of the line. This line was moved NW with storm motion and was run from NW to SW, during which ARMAR noted stratiform precipitation at the beginning and moderate rain near the middle. The CPI and CPP experiments noted good particle sizes during the run.

The next line was oriented SW - NE. AMPR and ARMAR noted good precipitation throught the leg. ARMAR noting that it was particlarly heavy near the end. This line was repeated with similar observations noted.

The on the next line oriented SW - NE, AMPR noted a good ice signature in the 85 GHz band and ARMAR reported high level moderate rain. The CPI and CPP continue to collect good data during this line. This line was repeated and similar observations were noted.

The DC-8 landed at 2118 UTC approx. using 2.4 flight hours leaving 71.6 hours for research use.

Mission Scientist: Anthony Guillory

Citation Chief Scientist Summary

The Citation took off at 1917 UTC for a coordinated TRMM mission with the DC8. The Citation flew through some fairly vigorously growing cells along a line at 15, 18, 21, and 24 thousand feet. Relatively strong updrafts and several mm sized graupel were encountered in some of these cells. The Citation then went up to 35,000 ft and did a slow spiral through an anvil down to the base of the anvil near 24,000 ft. The aircraft then returned to base and landed at 2228 for a total duration of 3.1 hours.

Data Quality:

Most of the data looked good, with two exceptions. The FSSP is still not sizing correctly and the sensor wire on the King liquid water probe was damaged by graupel part-way through the flight. This was the last spare for this instrument that we had on hand in Kwajalein. It will be out until the spares ordered arrive.

Flight Scientist: Grainger