Flight 21: Midway Local (5 April, 2001)

Due to extensive bird traffic during daylight hours, this flight was planned for an evening takeoff (2000 hr) and a 0400 landing.  The flight was planned to head southwest to 20N, 165E in the vicinity of Wake Island to investigate a predicted enhancement of CO above 700 mb (~3km).  Some possibility of encountering stratospheric downwelling in the vicinity of Midway was also predicted.

Results: Although no stratospheric intrusions were encountered on this flight, the predominant signature was of stratospherically influenced air.  O₃ (70-100 ppbv) was often anticorrelated with CO and dew point, but correlated with NOy.  Changes in NOy were mostly due due HNO₃ while PAN changed little.  CO observations were often 100 ppbv or less, although values up to 150 were observed with the greatest values observed toward the northern end of the flight track.