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 28-29 August 1999 UTC, 29 August local

Significant low level convergence and upper level support gave rise to a broad region of deep convection during the early morning hours. By the 2000 general meeting, the precipitation had already moved past Kwajalein. There was an east-west oriented convective zone with several transverse bands both ahead and behind the main line. These convective regions dissipated at roughly the same time giving a broad, but inhomogeneous, stratiform rain region.

The aircraft took off just as the convection had weakened significantly. Since the leading edge of the convective zone was just approaching the far end of our quantitative radar coverage (150 km) an attempt was made to sample the convection before it moved out of range. The aircraft were directed toward a mature convective segement with one end of the leg directed into stratiform rain. By the time the aircraft arrived, this convective region had weakened considerably. A few passes were made along this line. The Citation took samples at 12K and 15 K ft before being directed to a region of heavy stratiform rain for a spiral. The spiral was conducted both upwards and downwards as the DC-8 bow-tied the center point. This should be an excellent example of a microphysical profile (15K ft to 24 K ft) coupled with the ARMR and AMPR sampling by the DC-8.

The convective zone of the storm system made a ~15 mile discrete propagation to the southwest with vigorous convection (~12-14 km tops, reflectivity ~40 dBZ). Meanwhile, a new convective system was forming east of Kwajalein and moving toward the southwest. There was sufficient distance between these two systems for the second one to have plenty of untapped energy available to it. The Citation was directed to the new system after completing their spiral. The DC-8 was sent to sample the back edge of the convection forming the new convective zone of the old system. The single DC-8 pass down the back side of the convective zone of the first system showed heavy rain, cold brightness temperatures at 85 GHz, and ARMR reflectivity >45 dBZ. The DC-8 track at 39K ft also led to sampling of one particularly deep turret. Good microphysical samples were obtained.

The two aircraft were directed to the second system which was beginning to organize. This storm had a ~60 km long convective band with an very intense cell (15 km tops, reflectivity > 40dBZ) at the center of the line. Short transverse bands formed at the southern end of the line, giving the convection a T-shaped pattern (and making it difficult to direct aircraft). The Citation made numerous passes through all but the most intense cells. That aircaft covered the altitude range from 15K ft to 33K ft in 3000 ft increments and then stepped down to 27K ft again before being directed to a spiral in a heavy stratiform rain region. The DC-8 made several (dozen or so) passes along the convective band and on the back side of the convection. Sampling was established to cover both the heavy rain in the convection and the lighter rain in the transition and forward stratiform region.

This second system was sampled from an intense line of active convection to almost complete dissipation. This should be an excellent documentation of the evolution of a linearly organized multicellular convective band that produced a fairly broad stratiform rain region.

As a side note, the TRMM overpass was neglected to maintain sampling of the evolving system. A few scattered cells existed within quantitative radar range and TMI coverage. But cells like these have been sampled frequently during KWAJEX.

Michael Biggerstaff, Aircraft Mission Coordinator

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Convair Chief Scientist Summary
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Citation Chief Scientist Summary
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Mission Summary for the second Citation Flight of 8/28/99:

The Citation took off 2309 UTC for a coordinated TRMM mission with the DC8. The aircraft initially flew along a line of convective cells at 12,000 ft and then made a spiral ascent up from 12,000 ft to cloud top at about 24,000 ft. A slow spiral descent was then made using a constant bank angle from 24,000 ft back down to 12,000 ft. We then went to a line of vigorous convective cells and made passes down the line in 3,000 ft intervals from 15,000 ft to 33,000 ft. The Citation then stepped back down from 33,000 to 21,000 ft in 3,000 ft increments. We then did a slow descent from 21,000 to 12,000 ft. The clouds were very workable today. There were good stratiform and convective clouds in the project area today. The Citation returned and landed 0301 UTC for a total mission time of 3.9 hours.

Data Quality:

The FSSP was still not useful, but new King probe wires were installed prior to takeoff. The new wires lasted until about 2/3 of the way through the flight before being taken out. All the rest of the probes appeared to be working well.

Flight Scientist: Grainger

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DC-8 Chief Scientist Summary
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