May 8, 1996

Mission Summary

DC-8 SUCCESS flight #216 [960216] (scientist: Eric Jensen)

SUMMARY: The flight successfully sampled cirrus anvil outflow from a mesoscale convective system. The cloud system was several hours old, and the anvil appeared to be dissipating. Flight legs sampled the outflow region, the anvil itself, and the air above the anvil.

Mission Objective

• sample aerosols in the outflow region from a convective system.
• sample aerosols above a collapsing convective system.
• sample ice crystals and interstitial aerosols in a cirrus anvil.

Flight Log

OPERATIONS
FLIGHT PLAN:
Essentially, we plan to fly around the edge of a mesoscale convective system located in the central and eastern part of the country. Legs will be flown along airways, resulting in a zig-zag in and out of the cirrus outflow anvil. We will initially climb out with the T-39 sampling our exhaust and head north. After about an hour, the T-39 will break off, and we will head north-east, following airways, toward Green Bay. On the way back, we will either continue sampling the anvil and outflow region, or attempt to sample contrails from commercial aircraft outside of the anvil. The ER-2 will follow the DC-8 on the outbound legs, and then break off to fly over the convective towers.

TAKEOFF/LANDING
The DC-8 left Salina at 17.00 UTC (12.00 noon local time) and returned to Salina at 21.30 UTC

FLIGHT REPORT
The T-39 followed the DC-8 on climbout, until we reached eastern South Dakota. After the T-39 broke off, we headed northeast to Minneapolis, then east to Green Bay. On the leg to Green Bay, we entered the anvil at 39 K'. Next, we flew northwest to Duluth (out of the anvil). From Duluth, we headed back toward Green Bay, first at 35 K'. When we were under the anvil, we ascended to 41 K' (above the anvil). We then headed back toward Salina through southern Wisconsin and Iowa. We flew 15 min. at 41 K', then descended to 39 K' to be in the anvil again. Eventually, we ascended back to 41 K' to see where the cirrus cloud top was located relative to the tropopause.

METEOROLOGY-REPORT
FORECAST: A large MCS (mesoscale convective system) is located over the northern-central plains. Just before takeoff, the northern edge of the outflow anvil is over southern Minnesota and Wisconsin. The anvil is expected to persist and creep northward throughout the day. The strong convection is expected to stay well to the south, over southern Iowa and central Illinois.
OBSERVATIONS: On the northern leg out of Salina, we flew through patchy cirrus, and flew just under a persistent contrail at about -35 - -40 deg. C. The cirrus anvil penetrated between Minneapolis and Green Bay was a few thousand feet thick and optically thin. Moderate turbulence was apparent when we entered the anvil. The MCS was evidently collapsing by the time we headed back, since we never penetrated a deep anvil. Only diffuse cirrus near the tropopause remained over Iowa when we flew through.

INSTRUMENT STATUS

• BALLENTHIN: no problems
• BAUMGARDNER: no problems
• BRUNE: no problems
• CHAN: no problems
• COGGIOLA: no problems
• COOPER: IN instrument froze up
• DADS: no problems
• FERRY: no problems
• GARY: no problems
• GERBER: no problems
• HAGEN: no problems
• HALLET: no problems
• HEYMSFIELD: no problems
• HUDSON: intermittant computer failures
• LAWSON: no problems
• RODGERS: no problems
• SACHSE: no problems
• TALBOT: no problems
• TWOHY: CVI had heater leak at the end of flight
• UTHE: no problems
• VALERO: no problems
• WEINHEIMER: no problems

Mission Highlights

• ice crystal sizes up to about 100 microns were observed in convective outflow cirrus between 37000ft and 40000ft over Wisconsin
• leaving the (northern) edge of the anvil, the tropopause abruptly dropped by 1km and warmed by 8K
• the cirrus layer (above Iowa) extended about 700 ft above the temperature tropopause
• Volatile CN were enhanced by factors of 10-30 in and above the anvil