The scientific objective for this flight was to characterize the structure of the boundary layer near Christmas Island as well as to observe the variation of gas phase concentrations with time of day. For this reason, we took off late in the morning, and attempted to make observations just off the coast of Christmas Island during the solar peak, before continuing our ferry to Hilo. Circles were extended to 24 min to provide better sampling times for aerosol chemistry and to provide improved statistics for turbulence calculations. In addition, we added a 5th circle at 100' to provide an estimate of the change in chemistry in the intervening 2 hours between the first and last circles at the surface. We also attempted to sample the Kilauea plume during the approach to Hilo, by circling around the Island of Hawaii in a clockwise direction before landing.

Takeoff was at 19:38. At 19:49 we climbed to 8000' to very clear air. There were some very low clouds above during the first 100' circle. We started the 100' circle at 20:26:07 in a clockwise direction from a heading 060. The circle completed at 20:50:07 and we climbed to 1500'. At 20:53:21 we started the 1500' circle in a counterclockwise direction from a heading of 240. This circle ended at 21:17:21 and we climbed to 2300'. Porter reported 3025 and 3760 are functioning properly now. At 21:20:30 we started the 2300' circle in a clockwise direction from a heading of 060. This circle was completed at 21:44:30 and we climbed to 4400'. Porter reported that the 3025 is off line. At 21:57 we headed north and began porpoising at 1000'/min. More clouds have appeared since we began the first set of circles. Puffy clouds were present at this altitude (1500'), so we decided to complete the fourth circle at this level. At 22:09:19 we started a second circle at 1500' in a co! unterclockwise direction from a h

At 23:01 we climbed at 750'/min and began to fly toward Hilo. Scattered broken low clouds were present, and their tops appeared to be at ca. 3000'. The inversion was estimated to be at about 4600'. At 23:22 Hudson and Porter reported a layer of high aerosol concentrations at 14,500'. At 23:39 McMurry reported evidence of small but significant concentrations of UFAs at an altitude of ca. 21,000'. At 23:40 reported NO between 50 and 100 ppt. OH concentrations were about 2x10^6 and H2SO4 was under 10^6.

At 02:16 we started a profile down at 750'/min. There were still scattered clouds and the radar image indicated some precipitation in the area. At 02:40 Porter reported the 3025 was malfunctioning. At 02:48 we began circling the Big Island of Hawaii at ca. 1500' from the Southeast towards the West then North. At 03:01 we measured high CN concentrations (ca. 1000 p/cc), with H2SO4 up to 2x10^7. At 03:13 CN of 7000 p/cc was reported with H2SO4 at 3x10^7 (see graph printout). At 03:30 we hit a large peak in CN that may have been the volcano plume (see graph printout). At 03:31 we headed in towards the airport, skimming just below cloud base.