This flight was planned to head due south from Midway to 20N then head due east in to Kona.  A 0530 takeoff was planned to avoid daylight bird traffic over the runway.  While the transit time to Kona did not allow the P-3B to take up a stationary pattern during sunrise, a constant altitude was flown throughout the sunrise period.

Results: Leaving Midway, the P-3B ascended to 17.5 Kft.  At this altitude, stratospheric influence was observed as O₃ increased from 50 ppbv to more than 100 ppbv while NOy increased slightly from ~200 to ~300 pptv and CO remained steady at ~100 ppbv.  Upon descending, the most promising altitude for the sunrise portion of the flight appeared to be about 13.5 Kft.  Flight at this altitude encountered modest variability for the first hour, however, shortly after sunrise O₃ rapidly rose from 70 ppbv to 130 ppbv and conditions became extremely dry.  This complicated any interpretation of OH with changing solar conditions.  The predominant signature over the remainder of the flight was of stratospheric influence with several episodes of O₃ exceeding 100 ppbv and O3 in the boundary layer of ~60 ppbv.  CO remained mostly around 100 ppbv or less except for a thin layer at 19Kft containing 150 ppbv CO.