Flight summary, flight 12 DC-8 Okinawa - Yokota 1 - 03/18/2001.
Title: Formosa strait and China outflow Objectives: (1) to
sample boundary layer outflow from China to the Formosa strait;
(2) to sample different types of Asian outflow during transit from
Taiwan to Yokota.
Execution: We flew from Okinawa (26N, 128E) SW to (23N, 118E),
at the southern end of the Taiwan strait, setting up for a spiral
at that SW point and a return wall. A solid stratus deck
prevented us from extending the spiral below 4Kft where most of
the outflow was forecast. We stopped the spiral at that altitude
and returned NE to (25N, 121E - midway in the Formosa strait) where
we found a break in the clouds and spiraled down to 1 Kft before
continuing to head NE. We then continued on a roughly NE
track to Yokota (36N, 139E) with extensive profiling and three
spirals.
Results: The objectives were met and the flight brought some new
perspectives on Asian outflow. The boundary layer leg in
the Formosa strait showed for many gases the highest concentrations
seen by the DC-8 so far in the mission (CO up to 520 ppbv, CO2 up
to 394 ppmv, elevated CH4, N2O, 3.3 ppbv
HCHO, 1 ppbv CH3CHO, high acetone, etc). The transit
from Taiwan to Yokota showed (1) strong post-frontal boundary layer
ouflow (CO ~ 250 ppbv), (2) a layer with CO in excess of 400 ppbv
at 10Kft, and no biomass burning tracers, possibly due to westerly
transport from the Szechuan Basin; (3) biomass burning enhancements
at 18 Kft (characterized by high O3 and nitriles); (4)
dust outflow at 8 Kft (seen by DIAL as layer of depolarizing aerosol,
and characterized in a 15-min leg in situ). The dust layer
contained high concentrations of large particles, very low peroxides,
low HO2, but otherwise everything was flat. Descent
to Yokota indicated layers of extremely high ozone (up to 165 ppbv)
with flat or depressed CO and CO2; biomass burning? Stratosphere?
These layers will probably be a recurring theme in our sorties
from Yokota.
Meteorological Summary DC-8 Transit from Kadena AFB to Yokota
AFB Henry Fuelberg
Relevant Flow Features
Surface-A developing wave cyclone was located just off the northeast
coast of Japan. It was moving toward the northeast. A
cold front extended southwestward, east of Kadena (it had passed
the previous late afternoon), and through the Taiwan Strait. Only
weak high pressure was behind the front.
Middle troposphere-Conditions were similar to those of the previous
flight day. The subtropical high was located just northeast
of the northern Philippines, and a short wave trough was between
Korea and Japan. There was westerly flow over the entire
flight area.
Upper troposphere-The polar jet stream was not as well defined
as the day before. The subtropical jet stream was strong,
but not as strong as the previous week. The center of the
jet stream was over southern Japan. Westerly flow dominated
the area.
Relevant Cloud Conditions
Upon leaving Kadena, deep convection was evident far south of
the area. These storms marked the leading edge of the cold
front that had passed Kadena the previous afternoon.
The Taiwan Strait contained extensive clouds due to the frontal
zone. In some areas, there was a solid overcast, preventing
a penetration of them. These clouds had tops of ~4,000 ft,
and bases of ~1,000 ft. When flying at 1,000 ft in the Strait,
we skirted the bases of these clouds. Cirrus clouds also
were extensive in the Strait. Much of the cirrus appeared
to be diffused contrails. Many commercial jets were observed
to emit long contrails which spread out with time.
During our first excursion to 1,000 ft, the front was intersected
at an altitude of ~3,000 ft. Above the front winds (e.g.,
5,000 ft) were from the southwest, below the front they were from
the northeast. As the DC-8 continued deeper into the cold
air, streamlines suggest that the air was farther removed from
the Asian Coast. This is supported by the smaller observed
values of some chemical species.
The wind shift described above also was observed during our descent
to 1000 ft that occurred near 0517 Z. Extensive stratocumulus
blanketed this location, with bases and tops of 2200 and 3600 ft,
respectively
The boundary layer run near 0700 Z was relatively cloud free.
A volcano was observed near 0750Z.