Flight summary, DC-8 flight 16 - Yokota local 4 -
03/30/2001.
Take-off time 3:16 am local (1816Z on 0329); flight duration 9.4
hours
Title: Sunrise photochemistry of Asian outflow Objectives:
(1) to examine the photochemical evolution of Asian outflow at
sunrise; (2) to determine the role of the ocean as a source/sink
of oxygenated hydrocarbons; (3) to conduct a MOPITT underpass.
Execution: This flight was intended as a suitcase flight to Okinawa,
but a generator failure early in the flight required that we return
to Yokota at the end of the flight. We transited to (28N,
125E), a center of high pressure off the China coast, arriving
at 1Kft at 2100Z (30 minutes before sunrise). There we set
up a repeated wall at 1 Kft and 9 Kft (above the inversion) with
20 minutes at each altitude and 1Kft/min altitude changes between
the two. We repeated that pattern until 0050Z and then
climbed to 37Kft at (28.5N, 133E) for a MOPITT underpass spiral
down to 0.5 Kft. We then climbed back to cruise altitude and returned
to Yokota.
Results: Cancellation of the Okinawa suitcase precluded the Taiwan
strait flight planned for 0331. Nevertheless the objectives
of the present flight were met. The sunrise experiment was
conducted under clear skies and weak and variable winds at 1 Kft,
and steady W winds (30kts) at 9 Kft. There was strong subsidence
capping the Asian outflow below 7 Kft. All instruments functioned. Vertical
profiling from 1 to 9Kft (conducted 8 times over the course of
the experiment) sliced through a persistent China outflow plume
at 4-6Kft (CO 350- 380 ppbv). The base of the inversion remained
at 7Kft throughout. There were a lot of ships in the area,
and a number of ship plumes were sampled on the 1 Kft leg (or so
it seems - we had spikes of NO but little aerosol enhancement). Oxygenated
hydrocarbons appeared to show little temporal variation over the
course of the experiment, either in the marine boundary layer or
in the pollution plume above, although they showed pronounced vertical
gradients. Climbing up towards the location of the MOPITT
overpass we sampled unexpected "mystery ozone layers" at
24-37Kft with complicated chemical signatures. The MOPITT
underpass was conducted in a clear area and showed low featureless
CO concentrations down to 5Kft with high concentrations (up to
200 ppbv) at lower altitude.
Meteorological Summary Yokota Local # 4 (Sunrise Flight) 30
March 2001
Relevant Flow Features
Surface-A
rapidly deepening wave cyclone was located near 38N, 148E. A
cold front extended south and west from the low center, but it
was far outside the flight area. Surface high pressure was
centered near 28N, 125E, i.e., near the location of the 4 hour
sunrise flight pattern. A weak low was developing over the Yellow
Sea.
Middle
troposphere-A major closed low was centered over the northern Sea of Japan. Westerly
flow dominated the area. A major ridge was located over central Asia,
while flow to the south of ~35N was more zonal in nature. Backward trajectories
showed that air on the northern portion of the flight track may have originated
over Europe.
Upper
troposphere-The jet stream was quite strong just south of Japan. A
rather broad region contained winds in excess of 160 kt. The jet
was strongest east of the Asian Coast. The split flow described above
continued in the upper levels.
Relevant Cloud Patterns and Other Goodies
A
broad shield of multi-layered clouds was associated with the major
wave cyclone described above. However, most of these clouds
were outside of the flight region.
The area
of the 4 hour sunrise pattern was totally clear at all levels. Winds
at 1000 ft generally were from the south, but had a more easterly component
on the eastward portion of the track. Speeds were less than 10 kt,
with almost calm winds on the eastward side. Thus, the center of
the high was very near the eastern edge of the flight track at 1000 ft.
Winds along the 9,000 ft runs were almost due westerly at speeds of ~ 30
kt. A surface based haze layer had a top near 6000 ft., and this
corresponded to the level of a pronounced wind shift, i.e., from westerly
above to southerly below.
The area
of the MOPITT underpass had only scattered small cumulus clouds with bases
near 4,000 ft and tops near 5,000 ft. There were no middle or high
clouds in the area.