Flight summary, DC-8 flight 17 - Yokota local 5 -
03/31/2001.
Take-off time 9:12 am local (0012Z); flight duration 7.5 hours
Title: Warm conveyor belt and cyclonic recirculation Objectives:
(1) to examine the "wrap-around" recirculation around
a kamikaze cyclonic bomb NE of Japan; (2) to sample the warm conveyor
belt ahead of a newer front pushed east from Japan (and responsible
for snow over Yokota that morning); (3) to provide DIAL support
to the ACE-Asia Twin Otter radiation experiment over the Sea of
Japan north of Iwakuni.
Execution: The flight track was a "box" around Honshu
and Hokkaido. We headed W to (35N, 131E) to overfly the Twin
Otter on their wall between (35.5N, 131.8E) and (35.7N, 131.7E)
at 0135-0138Z. We then headed NE to the northern tip of Hokkaido
at (45N, 141E) followed by a SE leg to (39N, 150E) to sample the
wrap-around circulation around the kamikaze cyclonic bomb that
had been sitting to the NE of Hokkaido for the past few days. From
there we flew SW to Yokota (36N, 139E), sampling the rising air
along the warm conveyor belt pushed east of Japan.
Results: We met our objectives and sampled complicated chemical
signatures associated with the warm conveyor belt and the cyclonic
recirculation. Climbing out of Yokota we saw considerable fine
structure below 10Kft associated with lifting of Japanese pollution
by the front sitting over the area at the time, and coarser pollution
structure above interwoven with stratospheric filaments (recirculation
around the kamikaze?). The 31Kft leg to Iwakuni was in and
out of the stratosphere. The Twin Otter overfly was conducted
in a clear patch in a broken cloud field with good functioning
of the DIAL. Heading NE over the Sea of Japan, we observed
a depressed tropopause at 18Kft (jet stream), complicated pollution
influences just below (the recirculation?) and direct Korean
outflow below 10Kft with everything elevated (200-250 ppbv CO). As
we approached the northern tip of Hokkaido the tropopause rose,
and we sampled extensive aged (?) pollution at all altitudes (CO
150-200 ppbv, high PAN, C2Cl4, nitriles,
moderately high SO2, HCHO, ). Heading back SE
and then SW we observed a range of Asian outflow layers at all
levels with different chemical signatures. The recirculating pollution
in the north showed moderately high CO (150-200 ppb), high C2Cl4,
PAN, nitriles, low HCHO, and was interleaved with stratospheric
filaments. The warm conveyor belt further south showed higher
CO (up to 300 ppb). NO was very low in the "recirculating
pollution" (< 10 pptv) but had a lot of structure with
values in excess of 100 pptv in the warm conveyor belt associated
with recent convection (high CH3OOH/H2O2 ratios). The
NO structure was probably associated at least in part with lightning.
Meteorological Summary Yokota Local # 5 31 March
2001
Flow Features:
Surface--A
major low pressure area was centered near 47N 158E. With a central
pressure of ~974 mb, this system previously had reached "bomb" status. A
developing low pressure area was moving up the eastern coast of
Japan. Although its central pressure was only ~1004 mb, it
produced widespread light snow and rain over eastern Japan during
the entire day. The cold front extending south of the low
reinforced the cold air already in place over Japan. A high
pressure area was located near Shanghai.
Middle
troposphere-The major closed cyclonic circulation was nearly vertically
stacked with its surface counterpart described above (47N 158E). A
short wave trof extending southwest of this system was associated with
the developing surface system.
Upper
troposphere-The closed cyclone continued, with an additional cyclonic center
located just west of northern Japan. This system was merely a trof
at lower levels. It produced light southerly winds along the northern
part of the flight track (an unexpected occurrence). The axis of
the jet stream stretched from just south of Japan toward the east-northeast.
The jet was quite intense, with strongest winds (~ 170 kt) located near
38N, 160E. Speeds near 100 kt were even as low as 500 mb.
Cloud Features and Other Goodies:
The
major cloud feature was a classic "comma" shaped pattern
associated with the developing low skirting the east coast of Japan.
Clouds at all levels were occurring in this area. The Stormscope
indicated a few lightning flashes east of Japan in the area of
the developing low. However, these flashes were few in number.
The area
of the Twin Otter overpass was mostly cloudy with middle and upper level
clouds. However, some breaks were present, and the two aircraft took
maximum advantage of this fortuitous event.
Stratospheric air was encountered during the southwestern part of the flight
track. This region was in the left entrance region of the jet streak described
above.