Flight 16: Yokota Local 2 (24 March, 2001)

This flight was planned to begin with an intercomparison leg at 17 Kft with the DC-8.  Following the intercomparison, low altitude sampling legs were planned along the southern coast of Japan and to the north in the Sea of Japan.  Model predictions indicated both regions should have surface outflow below about 6 Kft with cleaner conditions above.

Results:

The intercomparison leg at the beginning of the flight went well.  Conditions were fairly constant for most species, although ozone showed some variability ranging from 70 to 90 ppbv.  Other measurements showed increased structure during a period of turbulence about 13 minutes into the 20 minute intercomparison. Sampling along the southern coast of Japan did show surface outflow below 6 Kft as expected.  CO was highly variable with mixing ratios often in the 300 ppbv range and sometimes exceeding 400 ppbv.  NOy and SO₂ were consistently at ppbv levels.  Crossing Japan to the north, very different conditions were encountered over the Sea of Japan.  At all altitudes, CO rarely exceeded 200 ppbv and was often around 100 ppbv.  Although background levels for all species were lower, several plumes were encountered from the boundary layer up to altitudes of 10Kft with ppbv level enhancements in SO₂ and NOy (which had a large fraction attributed to PAN).  These plumes also contained large enhancements in CN and smaller enhancements in ozone, CO, and DP.  The Georgia Tech group reported that aerosol composition was similar to the north and south of Japan indicating a mixture of dust and anthropognic aerosol.  Despite the similarity in composition, aerosol mass loading was 5 times higher south of Japan as compared to the north.