DC-8 SUCCESS flight #215 [960215] (scientist: Eric Jensen)
SUMMARY: The basic flight went very well. We successfully generated and sampled persistent contrails. Analysis of the environment should indicate what conditions are required for persistence of contrails. We also sampled contrails laid in the tops of cirrus clouds.
OPERATIONS
FLIGHT PLAN:
The flights will take up to 6 hours.
Take off is planned for 1700 UT, 1200 LT.
We will stager takeoff with the ER-2 going first,
followed by the 757/T-39/DC-8.
All aircraft will proceed to the Nebraska pan-handle
at an altitude of 37 K'.
We will fly a 100 mile racetrack
aligned with the wind (250 deg.).
On the upwind legs
we will fly 7 min. below the contrail and 7 min. above.
The T-39 will remain within 2
miles of the 757.
On the upwind legs, the T-39 will sample the 757 exhaust.
On the
downwind legs,
the T-39 will offset so that the DC-8 can sample the 757 contrail.
The DC-8 will start about 10 miles behind the 757
and drop back if the contrail is
persistent.
On the way back, we will do the MMS maneuvers.
TAKEOFF/LANDING
The DC-8 left Salina at 18.05 UTC (13.05 noon local time) and
returned to Salina at 23.50 UTC
FLIGHT REPORT
We transited to the target location, and upon arrival it was immediately
apparent, on circuit one, that the 757
was making a persistent contrail at 37 K'.
We followed them at 27 mi separation and
then had them descend [leg2] to 35 K', and flew in
their contrail.
On the second circuit, both aircraft flew at 35 K'. We flew
in the 757 contrail and our contrail from the previous circuit (about 45 min.
old) was above us (about 1km wide and detected by the satellite).
On subsequent circuits at 37 K',
the contrail was only persistent
only the eastern edge. (The moist area slowly drifted away from the fixed
racetrack pattern).
As the contrail, layed by the 757, was not very long, we closed, on the
third circuit) in
from about 30 mi to less than 15 mi staying in the contrail (no sense for
radiation measurements) and it got very bumpy.
On the fourth circuit we stayed about 10-12 mi back, mainly just below
the two 'curly' 757 wakes.
Then on circuit five, [leg 9 and 10] we flew a circuit near the tropopause,
at 39 K', about miles back: Contrails were short and we crossed
only a occasions the 757 exhaust remnants.
Thus, for circuit six [leg 11 and 12] we descended to 35000ft and skimmed
(the top of) the cirrus cloud layer (up to 50um size ice-crystals).
All aircraft layed longer contrails and we sampled, starting at 17 mi back,
the 757 contrail
remnants in and out of the patchy cirrus tops. (On the downwind leg 12,
we took radiation measurements below the 757 contrails in the solar plane)
We finally performed MMS maneuvers on the transit back to Salina.
METEOROLOGY-REPORT
OBSERVATIONS:
In the region of the racetrack pattern, extensive cirrostratus were present
below, with tops at about 35 K'. There was a hole in the cirrus in the center
of our racetrack pattern over low level intermittent cumulus cells.
Upper tropospheric humidities were high, and persistent
contrails were observed. The tropopause was at about 39 K'.
INSTRUMENT STATUS
All instruments on all aircraft are functioning
except for Hudson's CCN counter.