Flight 19: Yokota Local 5 (2 April, 2001)
This was the second of two flights coordinated with the ACE-Asia
science team. The two aircraft again planned to sample both
as a team and separately in outflow over the Sea of Japan. Model
predictions indicated an axis of low level outflow predominantly
below 2 km over the Sea of Japan. The NCAR C-130 planned
to fly three stacked walls along the outflow at 133E, 135E, and
137E. A rendezvous with the NCAR C-130 was planned
for (38.5N, 134E) to execute a joint spiral under the Terra
satellite and jointly execute the stacked wall at 135E across the
outflow axis. This was to be followed by extended wall sampling
by the P-3B along the axis of outflow.
Results: The P-3B transited at 18Kft from Yokota AFB to the rendezvous
point over the Sea of Japan. Conditions along this leg were
clean (e.g., O3 50-60 ppbv, CO 90-100 ppbv, NOy 200-400
pptv). After joining the NCAR C-130, the joint spiral was
performed with some degree of interference from broken clouds. Flight
along the stacked wall was performed at altitudes of 500, 2000,
and 4500 feet. Along each of these legs, more polluted conditions
were encountered to the north, verifying the presence of the low
level outflow (e.g., 320 vs 250 ppbv CO, 4 vs 2.5 ppbv NOy, 2.5
vs 1 ppbv SO2). Although the low level outflow
was detected, along-axis profiling exposed an unexpected and more
polluted layer at a higher altitude. This layer was extensively
sampled (e.g., CO >400 ppbv, SO2 up to 8 ppbv, NOy
up to 4 ppbv, PAN 1 ppbv, etc.) and determined to be between 8.5
and 12.5 Kft. Toward the end of the flight, a descent was
performed at 41N, 137E. During this profile, the polluted
layer was found to be entirely within a cloud layer between 8.5
and 12.5 Kft. This was followed by a 20 minute leg at 500
feet heading due south. During this leg, a shift in wind
direction from 305 to 235 degrees signalled our crossing of the
surface front. An ascent at the end of this leg at 39N, 138E
resulted in a much cleaner profile providing a stark contrast to
the profile at 41N (e.g., CO <100 ppbv and NOy <400 pptv).