Flight summary, DC-8 flight 14 - Yokota local 2 - 03/24/2001.
Take-off time 8:20 am local (2320Z on 0321); flight duration 9.0
hours
Title: Convective outflow Objectives: (1) to sample
high-altitude outflow from intense convective activity developing
over SE Asia, China, and the western Pacific; (2) to conduct a
high-altitude intercomparison with the P-3, (3) to conduct a MOPITT
validation experiment.
Execution: The intercomparison between the two aircraft consisted
of a level leg at 17Kft with the two planes flying in parallel
(2000' apart) for 30 minutes. This leg was conducted upon
take-off from Yokota along a (33N, 137-140E) track. We then
flew SE to (24N, 150E) for a MOPITT underpass spiral from 35 to
0.5Kft and to sample expected convective outflow. From there
we flew SW to (21N, 140E) and then NW to (26N, 135E) where
we headed N, downstream of a thunderstorm developing to our W. We
conducted a spiral up at (29N, 135E) to sample outflow from the
storm but were restricted to 27Kft by ATC. We were
able to climb to 33Kft at (31N, 135E) and from there headed to
Yokota with a slow in-progress descent.
Results: The objectives were met and the flight yielded several
surprises. The intercomparison was a success: both aircraft managed
to operate at the same speed, air was dry, and skies were clear. There
was quite a bit of structure in ozone, anticorrelated with H2O
(stratospheric influence?), and a transition in air mass was seen
over the course of the intercomparison leg. On the leg SE
toward the MOPITT underpass we sampled structures indicative of
stratospheric filaments, aged Asian outflow in the lower free troposphere,
and deep convective outflow. At 35Kft at the MOPITT underpass
point we found the strongest pollution influence sampled so far
in the mission in the upper troposphere (CO 200 ppbv with
O3 80 ppbv, HCHO 200 pptv). This pollution reflected
a combination of industrial and biomass burning influences (high
C2Cl4, high CH3CN) and appeared from satellite imagery to originate
from deep convection over eastern China. The MOPITT underpass
spiral was conducted under clear skies with high-CO layers at 35Kft,
7 Kft, and 12 Kft. In the boundary layer at (24N, 150E) there
was a surprising level of pollution influence (O3 50
ppbv, CO 140 ppbv). Climb to 29 Kft at 21N indicated again
high levels of pollution associated with convective outflow, presumably
over eastern China. Further vertical profiling on the way
back to Yokota indicated surprisingly high levels of pollution
at all levels, with CO frequently above 200 ppbv.
Meteorological Summary DC-8 Yokota Local # 2 24
March 2001
Relevant Flow Features
Surface-Several
weak low pressure areas were relevant to the flight. The strongest was
over extreme northern Japan, while weaker lows were centered over the northwestern
Yellow Sea and over southeastern China (northwest of Taiwan). A weak
anticyclone was over central Japan. Surface flow over much of the flight track
was from the east or northeast.
Middle
troposphere-A closed cyclone was just north of Japan. Westerly
flow covered all of the flight track.
Upper
troposphere-The polar jet stream continued to be poorly defined
at 300 mb. However, the subtropical jet stream was well defined
at 200 hPa, with its axis over the flight track along ~30N. However,
unlike most previous flights, strongest winds were not near Japan.
Instead, one jet streak was over eastern China, while a second
stretched over Saudi Arabia and northwestern India. Maximum
jet stream speeds appear to have weakened since the start of TRACE-P.
Westerly winds were over the entire flight area.
Relevant Cloud Features
An
area of deep convection formed over eastern China the previous
day. It was the biggest area of Asian convection seen thus far. The
area moved eastward into the western Pacific during the night.
By 2030Z on the flight day, the storm complex was near 28N, 128E. Water
vapor imagery revealed a plume of vapor extending eastward from
the storms, remaining evident as far as 148E. The storm
area moved southeastward during the flight. At 0700Z the
storms extended along 134E from 23-26N. A second area of
deep convection formed during the day near these same latitudes
but between 140-147E. For the first time during TRACE-P,
the Stormscope detected a number of lightning flashes.
Clouds conditions near the DC-8 - P-3 rendezvous were ideal.
Only small scattered cumulus and thin scattered cirrus were observed. Ideal
cloud conditions also covered the MOPITT underpass area. Isolated
small cumulus had bases near 2800 ft and tops near 4800 ft. A
few thin cirrus strands were along the northern portion of the
spiral area. However, they did not appear to be directly
overhead at any time.
The
second boundary layer run (near 0440Z) had scattered cumulus with
bases near 2,200 ft and most tops near 3,000 ft (although a few
tops reached 5,000 ft). On the other hand, the third boundary layer
run (near 0546Z) was characterized by an overcast layer of multiple
layered clouds. Rain occurred during part of this run. During the
ascent, the main cloud layers had tops of ~19,000 ft. However,
broken cirrus was at even higher altitudes.