Take-off time 3:16 am local (1816Z on 0329); flight duration 9.4 hours  

Title: Sunrise photochemistry of Asian outflow  Objectives: (1) to examine the photochemical evolution of Asian outflow at sunrise; (2) to determine the role of the ocean as a source/sink of oxygenated hydrocarbons; (3) to conduct a MOPITT underpass.  

Execution: This flight was intended as a suitcase flight to Okinawa, but a generator failure early in the flight required that we return to Yokota at the end of the flight.  We transited to (28N, 125E), a center of high pressure off the China coast, arriving at 1Kft at 2100Z (30 minutes before sunrise).  There we set up a repeated wall at 1 Kft and 9 Kft (above the inversion) with 20 minutes at each altitude and 1Kft/min altitude changes between the two.   We repeated that pattern until 0050Z and then climbed to 37Kft at (28.5N, 133E) for a MOPITT underpass spiral down to 0.5 Kft. We then climbed back to cruise altitude and returned to Yokota.  

Results: Cancellation of the Okinawa suitcase precluded the Taiwan strait flight planned for 0331.  Nevertheless the objectives of the present flight were met.  The sunrise experiment was conducted under clear skies and weak and variable winds at 1 Kft, and steady W winds (30kts) at 9 Kft. There was strong subsidence capping the Asian outflow below 7 Kft.  All instruments functioned.  Vertical profiling from 1 to 9Kft (conducted 8 times over the course of the experiment) sliced through a persistent China outflow plume at 4-6Kft (CO 350- 380 ppbv).  The base of the inversion remained at 7Kft throughout.  There were a lot of ships in the area, and a number of ship plumes were sampled on the 1 Kft leg (or so it seems - we had spikes of NO but little aerosol enhancement).  Oxygenated hydrocarbons appeared to show little temporal variation over the course of the experiment, either in the marine boundary layer or in the pollution plume above, although they showed pronounced vertical gradients.  Climbing up towards the location of the MOPITT overpass we sampled unexpected "mystery ozone layers" at 24-37Kft with complicated chemical signatures.  The MOPITT underpass was conducted in a clear area and showed low featureless CO concentrations down to 5Kft with high concentrations (up to 200 ppbv) at lower altitude.

Relevant Flow Features

         Surface-A rapidly deepening wave cyclone was located near 38N, 148E.  A cold front extended south and west from the low center, but it was far outside the flight area.  Surface high pressure was centered near 28N, 125E, i.e., near the location of the 4 hour sunrise flight pattern. A weak low was developing over the Yellow Sea.
         Middle troposphere-A major closed low was centered over the northern Sea of Japan.  Westerly flow dominated the area.  A major ridge was located over central Asia, while flow to the south of ~35N was more zonal in nature. Backward trajectories showed that air on the northern portion of the flight track may have originated over Europe.
         Upper troposphere-The jet stream was quite strong just south of Japan.  A rather broad region contained winds in excess of 160 kt.  The jet was strongest east of the Asian Coast.  The split flow described above continued in the upper levels.

Relevant Cloud Patterns and Other Goodies

         A broad shield of multi-layered clouds was associated with the major wave cyclone described above.  However, most of these clouds were outside of the flight region.
         The area of the 4 hour sunrise pattern was totally clear at all levels.  Winds at 1000 ft generally were from the south, but had a more easterly component on the eastward portion of the track.  Speeds were less than 10 kt, with almost calm winds on the eastward side.  Thus, the center of the high was very near the eastern edge of the flight track at 1000 ft. Winds along the 9,000 ft runs were almost due westerly at speeds of ~ 30 kt.  A surface based haze layer had a top near 6000 ft., and this corresponded to the level of a pronounced wind shift, i.e., from westerly above to southerly below.
         The area of the MOPITT underpass had only scattered small cumulus clouds with bases near 4,000 ft and tops near 5,000 ft.  There were no middle or high clouds in the area.