DC-8 SUCCESS flight #204 [960204] (scientist: Eric Jensen)
SUMMARY: This flight turned out to primarily be a cirrus profiling mission. Reports from the ER-2 and the ground indicated that the T-39 did not generate persistent contrails. There were occasional indications of contrail crossings. It was a very successful cirrus sampling flight. Patchy cirrostratus were present most of the time during our crosswind pattern south of the CART site.
DC-8 FLIGHT 204
OPERATIONS
FLIGHT PLAN:
Planned takeoff: 17.00 UTC (12.00 local time) for a six hour flight.
Part 1:
The T-39 will first fly a set of 4 10-mile-diameter circles
centered 10 mi. upwind of the CART site. Next, the
T-39 will fly 4 10-mile-diameter circles centered 20 mi. upwind of
the CART site. Finally, 4 more circles 30 mi. upwind of the CART
site.
Assuming a 60 knot wind speed, it will take about
30 min. for the contrails to advect 30 mi. downwind of the CART
site where the DC-8 will begin sampling them. During this time,
the DC-8 should profile any cirrus in the area while staying
at least 30 mi. downwind of the CART site. Once the T-39 contrails
have advected 30 mi. downwind of the CART site, the DC-8 will fly
4 10-min. flight legs normal to the wind, crossing the T-39 contrails.
Each flight leg will be 10 mi. closer to the CART site such that the
4th leg will go over the CART site. After the 4th leg, the DC-8 will
fly downwind to 30 mi. downwind of CART site and again fly 10 min. legs
normal to the wind. The first 3 legs should all be at 30 mi. downwind
of CART site so that old DC-8 contrails can advect out of the way.
The 4th, 5th, and 6th legs will then be at 20, 10, and 0 mi. downwind,
respectively.
The ER-2 will fly tracks over the CART site, aligned with the wind
for the duration of the mission. The track should extend 20 mi. upwind
of T-39 circle and 60 mi. downwind of CART site (maximum 110 mi. flight
track).
Part 2:
After the T-39 heads home, the DC-8 will fly straight legs
inclined 10-20 deg. to the wind. The legs will be about 20 min. long.
The objective will be to fly back up the contrail from the previous leg.
The upwind leg will cross several miles upwind of the CART site such that
the contrail advects over the CART site before the DC-8 flies back up its
contrail.About 4 legs will be flown. The ER-2 will continue flying upwind
and downwind over the CART site extending just upwind and downwind of the
DC-8 contrails.
After the last contrail-sampling leg, the DC-8 will fly directly
upwind over the CART site and continue upwind 60 miles. The ER-2
will fly a few hundred mi. downwind from the CART site to image old
contrails.
TAKEOFF/LANDING
The DC-8 left Salina at 17.05 UTC (12.05 am local time) and
returned to Salina at 22.50 UTC
FLIGHT REPORT
The CART site relayed cirrus altitudes at 27000, 33000 and 35000ft.
The Sabre-liner left Salina at 17.00 UTC
to make circle contrails about 10 miles
upwind of the CART-site at 35000ft.
The DC-8 left Salina at 17.05 UTC.
The DC-8 headed downwind of the CART-site for cross-wind cirrus profiling
(up and dn 10 minute flight-legs) at first at 27000ft (2 legs), then at
31000ft (2 legs) and finally at 35000ft (4 legs) - at that altitude also
to sample aged T-39 contrails.
At 27000ft 'tons of particles' were detected in patchy cirrus by the
Lawson probe and by the 2DC-probe. On the second leg there was a short
power failure.
(Converter 1 died at 17.30 UTC and it
took a few minutes to bring back up.)
At 31000ft cirrus streaks were seen above and below and in the
vicinity, though it also appeared cloud-free locally.
Persistent contrails were seen above.
At 35000ft the DC-8 layed a contrail (started to do so at 32000ft - 18.00 UTC,
which was detected by the ER-2 pilot from above).
Commercial aircraft crossed above and layed contrails, that lasted about
20 km, but they were not persistent. The DC-8 was skimming along the
top of patchy cirrus, with nice fallstreaks to lower elevations.
Cirrus was observed at all three altitudes (no low and mid level clouds),
fallstreaks were mainly below 30000ft.
Cirrus was more frequent and optically thicker towards the northern
sections of the north-south flight legs. Cirrus was patchy and often it
appeared that the aircraft was flying in cloud-free air with cirrus all
around. With increasing altitude there were less particle counts on the 2DC
probe, though many small crystals (10um size and smaller) were detected
by the replicator (Hallet) and by the VIPS (Heymsfield).
The CART site indicated that the DC-8 was
generating a persistent contrail at about 18:25 UTC.
The temperature was about -62C.
MTP reported that the tropopause
was at about 39000ft most of the flight.
For most of the pattern, the lidar was restricted to scanning
below 0 degree.
On the fourth leg at 35000ft the DC-8 passed over the CART site. We
noticed (possible T-39) contrail left-overs below us (18.50 UTC).
The ER-2 reports seeing T-39 and DC-8 contrails, however,
these contrails are non-persistent. It was decided to climb to 37000ft.
The T-39 (on request) climbed to 37000 ft, while the DC-8 made four more
flight legs at 35000ft to catch remnants of T-39 contrails.
On these legs the DC-8 - at least once - crossed our own contrail: VIPS showed
many sub-10um crystals and relative humidity is above 100% (to ice).
At 37000ft the DC-8 was still creating contrails, though not persistent.
We passed several contrail remnants (T-39), though, there were difficult
to identify visually, due to cirrus break-off and smoke from fires at
the surface.
The T-39 returned, and as the DC-8 were unable to create persistent contrails
it was decided to profile the cirrus/contrail cloud deck.
The DC-8 descended to 29000ft and flew east-west flight legs at over the
CART site.
At 29000ft DC-8 did not produce any contrails. The CART site
was obscured by a thicker cirrus patch.
At 32000ft, DC-8 started to produce a slight contrail, but lost that ability
towards the end of the flight-leg (winds 70kn/ 266deg).
At 35000ft (above 33000ft) the DC-8 made contrails again.
The DC-8 passed several aged contrails (slightly below) indicated also
by chemistry measurements. The relative humidity (DADS) is shown to be
consistently above 115%.
The DC-8 altitude at 37000ft was cancelled and instead the DC-8
returned into its own contrail: great data! (NO, NOy, CN, VIPS).
We measured in the DC-8 contrail for
several miles. Early on, the contrail was embedded in the cirrus top, then in
clear air. The aircraft was maneuvered such that both wingtips could sample the
contrail.
Finally, the DC-8 climbed into the stratosphere (tropopause at 39000ft).
At 41000ft (-64C, 140% (?)) the DC-8 laid long (though not persistent)
contrails. Contrails were clearly visible during a slow wide turn.
The DC-8 then descended (at 22.00) in an Eulerian spiral (not exceeding 1000ft
descent per minute) over the CART site in optically thin cirrus, as the
ground was visible during the spiral.
Some wiggling MMS maneuvers were flown on the return to Salina.
Landing (in strong southerly winds) occurred at 22.50 UTC.
METEOROLOGY REPORT
Forecast: Thin cirrus (possibly thick). High humidities in upper
troposphere. Tropopause height of about 12 km.
Observations: As expected, tropopause was high and cold near 12 km
and about -65 C. No mid-level or low-level clouds, though cirrus. Cirrus
was freqently patchy and thickend up as the day progressed. Many contrails
were oberserved though not always very persistent (passing planes).
The DC-8 preduced contrail above 32000ft well into the stratosphere.
INSTRUMENT STATUS
The Gerber probe was not on the plane.
The three stage hygrometer pump was broken and was replaced by a two stage pump.
The Lawson probe was back on.
