Flight 15: Yokota Local 1

This flight to the east of Japan was intended to profile across a frontal boundary near 150E, sample beyond the front, and cross the frontal zone again on the return to Yokota.

Results:  Heading out to the frontal zone, vertical profiles revealed ozone to be about 10 ppbv lower beyond the front.  CO values were similar below 8 Kft and were lower beyond the front at higher altitudes.  CO values were rather low both behind and beyond the front falling mostly in the 100-200 ppbv range.  The vertical ascent at 40N fell within the frontal zone and showed almost no gradient in the CO (120 ppbv) and ozone (60 ppbv)profiles while relative humidity was near 100% between the surface and 15 Kft.  Returning across the frontal zone, CO values remained less than 200 ppbv until reaching the boundary layer.  At 5.5 Kft, evidence of new particle formation was reported by the UH group, and both ultrafine and fine particle counts showed a strong correlation with variations in NOy.  On the final boundary layer run, polluted air with CO up to 400 ppbv and NOy up to 3 ppbv were observed.  PAN was measured to be the dominant NOy species through most of the flight often accounting for 40-50% of total NOy.  On the approach into Yokota, strong pollution encountered at 4 Kft included CO in excess of 700 ppbv, CO₂ in excess of 400 ppmv, NOy greater than 20 ppbv, and PAN over 3 ppbv.