Flight summary, DC-8 flight 13 - Yokota local 1 - 03/21/2001.
Take-off time 8:20 am local (2320 Z on 0320); flight duration
9.4 hours
Title: Frontal lifting and dust outflow
Objectives: (1) to characterize the lifting of Asian outflow
by a cold front, (2) to sample convective outflow from SE Asia
in the upper troposphere (3) to sample dust and pollution outflow
near the China coast, (4) to sample the stratosphere subsiding
on the north side of the jet stream, (5) to conduct a MOPITT validation
experiment in background tropical air.
Execution: We flew from Yokota (36N, 139E) SW to cross an active
cold front (vertical profiling) and conducted a MOPITT validation
spiral from 35 to 0.5 Kft at (22N, 130E). We then flew NW
to (30N, 125E), re-crossing the front with vertical profiling,
and conducted a N return leg into the Yellow Sea to (35N, 125E)
to sample dust and pollution outflow. From there we climbed
to cruise altitude and returned to Yokota.
Results: All objectives were met. On the climb up from Yokota
we sampled the "high-ozone layer" (90 ppbv O3, flat CO,
depressed CO2, high HCHO, PAN, nitriles) which appears
to originate from aged biomass burning (although exact origin is
still a mystery). Fresher biomass burning outflow, most likely
of SE Asian origin, was sampled at 31Kft on the SW leg from Yokota
to (22N, 130E). Crossing of the front at (36N, 136E) was
conducted under particularly active conditions below 10Kft, with
considerable structure in the frontal cloud outflow reflecting
fresh lifting of Asian pollution (high CH3OOH/H2O2 ratio, high
C2Cl4, high nitriles, considerable fine structure in CO, CO2,
CH4, N2O). Continuing SW, as we got
in the boundary layer at 1Kft we returned on the cold side of the
front (CO over 300 ppbv, acetone over 1 ppbv). This boundary
layer outflow was capped at 5Kft, as seen in previous flights;
above that altitude we were on the warm side of the front with
clean air and little structure. Our MOPITT spiral (delayed
30 min because of ATC) was conducted in a relatively featureless
atmosphere with only a modest boundary layer enhancement of CO. On
our flight NW we re-crossed the front at 26N, sampling lifted Asian
pollution at 12 Kft (CO up to 210 ppb, CO2 above 382
ppmv), and we then hit considerable Asian pollution behind the
front heading north in the boundary layer, including in particular
a well-defined crossing of the Shangai plume at 30N (CO up to 1240
ppbv, O3 up to 140 ppbv, HCHO 8 ppbv, Acetone 6 ppbv, HCN 2 ppbv,
PAN 6 ppbv, high SO2, CH4 up 10-15%, etc). There
was strong evidence of dust associated with this plume (yellow
aerosol filters!). The pollution was capped at 5Kft by a
dry subsiding air mass with low CO. Heading further north
into the Yellow Sea we identified dust layers mixed with pollution
using the DIAL depolarization signal and conducted boundary layer
sampling in a mixture of pollution and dust. The dust-pollution
mix was in contrast to the "clean" dust layer sampled
on the Okinawa-Yokota transit. Climibing up on our return
leg from the Yellow Sea we entered the stratosphere at 29Kft and
stayed there for most of our return to Yokota.
Meteorological Summary DC-8 Yokota Local Number 1 Henry
Fuelberg
Relevant Flow Patterns
Surface-A
low pressure area was centered over extreme northern Japan. A cold front extended
from it-first toward the southeast along 150E, and then southwest toward Taiwan. The
surface high pressure behind the front was relatively small. A developing
low pressure area was located over northeastern Asia.
Middle
Troposphere-A closed low was located just north of Japan. It was
the middle level reflection of the surface cyclone described above.
The subtropical high was located near 19N, 140E. Westerly
flow dominated the flight track.
Upper
troposphere-The subtropical jet stream was oriented just south
of Japan. Strongest speeds (the jet streak) stretched from east
to west from south of Tokyo to near Okinawa. Westerly winds
covered the entire flight track.
Relevant Cloud Patterns
The
overall pattern was a band of middle and upper clouds stretching
from south of Tokyo to near Hong Kong. The cloud band was
widest just south of Tokyo and quite narrow on its southwestern
edge. Low level clouds covered much of the flight track. Details
area given below.
First
boundary layer run-The DC-8 penetrated the frontal zone from above
at an altitude of ~5,000 ft. Winds below were from the northwest,
and from the west above. Rain was encountered in the area. Considerable
turbulence was encountered due to the convective nature of the
clouds. We apparently did not pass into the warm air while
at 2,000 ft, but were close to the leading edge of the front
MOPITT area-Only scattered cumulus were in the area. Bases
were near 1500 ft, and tops near 5,000 ft. Some cirrus were south
of the cloud track. Due to ATC problems, the DC-8 had to
circle the area before descending. Contrails were created
during this time.
The
DC-8 crossed the surface position of the front a second time as
it headed northward along the western portion of the flight track