Mission Summary for 18 August, 1999
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Aircraft Coordinator Summary
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Mike Biggerstaff, Aircraft Mission Coordinator
Mission Summary for 18 Aug UTC, 18 Aug LT. This was the second flight mission of the day.
All times below are in UTC
Single aircraft: Citation
Citation t/o ~0213, land ~0445 (not exact)
TRMM overpass: None during this time.
After a successful mission earlier in the morning the Citation refueled and was ready to go again during the afternoon. The need for robust statistical sampling of microphysics from the melting level to -30°C can be met with the Citation during single aircraft missions. Moreover, processes studies such as evolution of a particular cell or semi-Lagrangian sampling of microphysical evolution just above and through the melting level is easier to address during single aircraft missions.
Once airborne the Citation was directed to a short multicell band of moderately strong convection in the southern portion of the western dual-Doppler lobe. Coordination with the ship and KMR radars will aid in linking the observed microphysics to cloud dynamics. One cell at the western end of this line was particularly strong with echo tops to 14 km and 30 dBZ to just over 6km. As in the earlier flight, all echo was moving rapidly (20+ knots) from east to west. The Citation made several passes through this line starting at 14K ft altitude and working up to 17K ft in 1000 ft intervals.
While working this line, a strong cell moved across Kwajalein dropping 0.53" of rain and producing a cloud-to-ground lightning strike. The cell was weakening slightly as it moved further westward. Another strong cell was located about 10 miles south. The Citation was directed towards these two cells. The cells weakened rapidly as the Citation approached. One pass was made at 27K ft (the level of maximum reflectivity in the anvil from the cells) on the eastern side of the precipitation. Another pass was made through the dissipating cells on the western end. The flight altitude was decreased from 27K to 21K ft in 3000 ft intervals on subsequent passes though the dissipating cells.
The cells further weakened producing a small region of precipitation with weak horizontal gradients in reflectivity. Some would refer to this as stratiform rain. The Citation made two spiral descents through part of this stratiform rain. The region was not widespread and much of the descent was in rather weak reflectivity.
Several fast-moving short band of cells formed along the southern range of the radar display (150 km). These cells were all less than 8 km deep. Given the range and their character, it was decided to recommend that the Citation return to base after the second sprial descent was completed. That recommendation was accepted.
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Citation Chief Scientist Summary
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Mission Summary for the Citation Flight of 8/18/99.
The Citation took off at 0214 UTC for a precipitation study on the clouds available in the area, which contained convective and stratiform precipitation areas. Most of the time was spent to the southwest of Kwajalein. Several passes through convective cells were made at 14,000 ft, 15,000 ft, and 16,000 ft. In climbing to 17,000 ft, the Citation was out of cloud as the cells had been weakening and were dissipating. The aircraft was directed to a new area and climbed to 27,000 ft with the intent of stepping down through this system at 3,000 ft increments. By the time the aircraft was down to 21,000 ft, the cells had dissipated and were no longer identifiable. There was a fairly large area of precipitating stratiform cloud at this time and an attempt was made to do a spiral descent down through it, starting at 29,000 ft. As we went below 19,000 ft, the cloud was no longer intact. We then moved to a more promising area and began a spiral descent there from 19,000 ft. Unfortunately, there was an airspace conflict and we were held for some time at 18,000 ft before being allowed to continue the descent. By the time we reached an altitude of 15,000 ft, the cloud had dissipated. As there seemed to be no active areas in the project area, the c Citation returned to base, landing at 0444 UTC for a total time of 2.5 hours.
Data Quality:
The instrumentation on board the aircraft appeared to be functioning well, with the exception of the FSSP and some of the real-time displays which has been mentioned in previous discussions.
Flight Scientist: Grainger