Flight 17: Yokota Local 3

This flight was planned to investigate air-sea exchange through eddy correlation measurements based on high frequency sampling of SO₂ and CO₂ and data from TAMMS.  The flight was planned for the marine boundary layer to the southeast of Japan (vic. 34N, 145E) where clear air and subsident conditions were expected to prevail, although the level of heterogeneity to expect in the airmass was uncertain.  Potential problems with a volcanic plume from Miyake Jima were forecast by the U. Iowa model.  A coincident overpass of the Terra satellite also offered an opportunity to provide a profile of aerosol properties useful in the validation of MISR. 

Results:

On the initial descent into the boundary layer southeast of Japan, intense pollution was encountered below 4000 ft with 2 ppbv NOy, 20 ppbv SO₂, up to 300 pptv NO, evidence of new particle formation, etc.  This layer was most likely a mix of pollution and volcanic emission from Miyake Jima.  Stacked legs of 30 minute duration were flown in an L shape along and across the wind at 500, 800, and 1200 feet with a porpoising leg at 1800 feet.  While conditions were not homogeneous, variations along the legs were consistent with one end being polluted and the other being relatively clean.  After another sounding, another set of stacked legs were flown more to the south at altitudes of 500, 700, 1000, and 1200 feet.  While the second set of legs began with more homogeneous conditions, the plume from Miyake Jima was clearly encountered along a portion of each leg with highly elevated SO₂ and CN with no response in other pollution tracers.