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.