Flight 18: Yokota Local 4

This flight was planned in coordination with the ACE-Asia science team which had just arrived at Iwakuni MCAS, Japan.  A rendezvous with the NCAR C-130 was planned at 18 Kft over the Sea of Japan to be followed by several hours of proximity flying to the southwest between Japan and Korea and south along 129E sampling across a predicted axis of outflow from China associated with a frontal passage.  Some special planned maneuvers included a spiral sounding from 18 Kft to 500 feet at the rendezvous point and another sounding to 12 Kft coinciding with an overpass of the Terra satellite.  With a primary focus on trace gases for the NASA P-3B and a focus on aerosol properties on the NCAR C-130, this flight offers an unprecedented level of detail in characterizing the state of the atmosphere.  It also provides a bridge between the aircraft for extending their datasets in terms of common measurements.  These include packages on both aircraft from U. Hawaii for particle measurements, Georgia Tech for aerosol composition measurements, and Drexel for SO2 measurements.  Other common measurements include ozone, CO2, and nonmethane hydrocarbons.

Results:
The P-3B transited at 18Kft from Yokota AFB to the rendezvous point (37N, 133E) over the Sea of Japan.  Along this leg, high variability in all species were observed (e.g., CO 120-300 ppbv, NOy 400-1500 pptv, SO2 up to 1 ppbv).  High chloride values reported by the Georgia Tech group indicating the presence of sea-salt suggest that this variability was caused by pollution that had been lifted and wrapped around the low pressure system located to the northeast.  This system was the focus of the DC-8 flight for this day.  The rendezvous was executed as planned and was followed by a spiral descent to 500 feet in broken cumulus clouds.  This spiral was intended to allow column integration of in-situ aerosol measurements of aerosol optical depth for comparison to radiometer measurements on the NCAR C-130.  From this point proximity flying was executed at several altitudes going southwest to (33.5N, 129E) then south to (29N, 128E).  Along these legs, pollution was encountered mostly below 8000 feet with the most intense pollution centered around at 3000 feet (e.g., sustained values of CO 300-350 ppbv, NOy 5-6 ppbv, NO over 700-1500 pptv, PAN 1-1.5 ppbv.  A spiral ascent from 500 feet to 12 Kft and an immediate descent to 3 Kft was executed under clear skies at (31.5N, 128.5E) to coincide with the overpass of the Terra satellite.  After 3 hours of proximity flight, the aircraft separated at (29N, 128E) with the P-3B heading back to Yokota.  Flying to the south of Japan, layers of pollution and stratospheric influence (ozone up to 200 ppbv) were encountered between 12 Kft and 19 Kft in a region predicted to be along a boundary between stratospheric air and polluted air.