DC-8 SUCCESS flight #211 [960211] (scientists: Brian Toon and Eric Jensen)
SUMMARY: The flight was primarily successful: We did find and sample a wave-cloud. Measurements in and around the cloud should be very interesting. Sampling the 757 plume was more difficult than expected. We did not get closer than about 10 mi., we were not directly along the wind, and the 757 was not making a substantial contrail.
DC-8 TEST-FLIGHT
take advantage of the simple, well-defined dynamics and
sharp cloud boundary at the leading edge of wave clouds
over the Rocky Mountains:
OPERATIONS
FLIGHT PLAN:
Part 1: Transit to New Mexico with DC-8 sampling 757 exhaust
The 757 and T-39 will take off together and fly in formation to New Mexico.
The DC-8 will take off shortly after the 757 and T-39, and follow them
at 10-20 miles out.
We will attempt to sample their exhaust and see how close we can get without
too much turbulence.
Part 2: Wave Cloud sampling and seeding programs
Starting near the highest point in the wave-cloud,
we will fly upwind, following
potential temperature surfaces,
through the leading edge of the cloud and upwind 15
min. Then we will turn and fly back up our exhaust trail back into the cloud.
Next, we will turn 270 deg. and fly a 10 min. leg normal to the wind, along the
leading edge of the cloud.
Finally, we will execute a dog-leg turn and fly another
10 min. leg along the leading edge of the cloud,
attempting to intersect our exhaust
trail flowing into the cloud. This pattern should take about an hour.
We will repeat this pattern 3 times. After the first pattern, the ER-2 should
arrive and fly a compact pattern above the leading edge of the cloud. No strict
coordination with the ER-2 is required other than sending them the point on our
track normal to the wind at the leading edge of the cloud.
Part 3: Transit back to Salina
TAKEOFF/LANDING
The DC-8 left Salina at 17.29 UTC (12.29 am local time) and
returned to Salina at 20.40 UTC
FLIGHT REPORT
During the transit to New Mexico (35 deg. 58 min., 105 deg., 30 min.), we
flew 15 min. legs at 18, 27, and 35 K' 10 mi. behind the 757. The wind was
about 30 deg. off our flight track, and the 757 generated only a small contrail
only on the 35 K' leg. We crossed the 757 exhaust plume several times, but
were never able to stay in it longer than a few sec. The plume crossings were
detected by minor turbulence and the chemistry and CN measurements.
At the designated wave-cloud point, a wave-cloud was present, but it was
at or above 41 K', so we had no chance of flying in it until the end of the
flight. We then headed south to a cluster of lenticular clouds that appeared
to be lower. We flew through these clouds several times at 28-29 K'. We were
unable to fly upwind due to a restricted area just upwind. We flew cross-wind
legs, attempting to fly upwind of the clouds, in the leading edge, in the
middle of the cloud, and downwind. The cloud cluster consisted of several
separate lenticular clouds with leading edges in different locations,
so the pilots
had to maneuver considerably
to stay in the leading edge as much as possible.
Eventually, we headed back to our original waypoint to sample the high
wave-clouds. When we got there we discovered that the bulk of the cloud
had shifted north. We flew through a thin patch of cirrus at 41 K', did
the MMS maneuvers, and headed back to Salina.
METEOROLOGY-REPORT
FORECAST:
Wave-clouds are expected over mountains in northern and central New Mexico
with relatively cold cloud tops. Short-lived contrails are expected during
the transit to New Mexico.
OBSERVATIONS:
Most wave clouds were above 40000ft and could not be reached.
INSTRUMENT STATUS
All instruments are functioning.
