Title: chemical evolution of frontal outflow  

Objective: (1) to sample the aged frontal outflow band that had been previously sampled as fresh frontal outflow on the 0307 flight; (2) to do laundry in Okinawa  

Execution: The frontal outflow sampled on 0307 was forecast to have been transported along a SW-NE axis over the following two days, resulting in a band of aged pollution over the western Pacific  The DC-8 flew east from Hong Kong to (20N, 150E) to sample aged free tropospheric outflow transported S ahead of this band and to reach the clean air ahead of the front at the easternmost waypoint; it then flew NW to Okinawa (26N, 128E) to cross and characterize this frontal band  

Results: The flight was a success  (1) Biomass burning pollution plumes were sampled extensively on the eastbound leg west of 135E  Further east, cleaner conditions were found, and the easternmost point was at the frontal transition  On the NW leg to Okinawa, the polluted frontal band (with CO up to 300 ppb) was encountered at 140-142E, as expected; behind this band and into Okinawa the conditions were much cleaner, with strongly subsiding air in the free troposphere  Free washing machines in Okinawa afforded astronomical savings over hotel prices for laundry in Hong Kong 

Meteorological Summary DC-8 Hong Kong - Okinawa  Overnight

Relevant Flow Patterns
         Surface-A low pressure area was centered near 30N, 155E.  A cold front extended southwest to near 20N, 140E, becoming diffuse farther south of that position.  High pressure was centered near Shanghai.  Northerly to northwesterly flow covered most of the flight area.  The major exception was northeasterly flow between ~ 20 - 25 N.

         Middle troposphere-A subtropical high was located near 20N, 160E. A short wave trough was located just east of Japan.  Westerly winds covered the flight area.  Easterly flow was south of Hong Kong.

         Upper Troposphere-Flow patterns were similar to those in the middle levels.  The northern part of the flight pattern traversed the right entrance region of the jet streak.
Relevant Cloud Patterns

         Middle level clouds blanketed the Hong Kong region, but dissipated during the eastward track.  Scattered low level clouds covered most of the flight track.  Most tops were less than 6000 ft.

         The DC-8 strived to pass beyond the surface frontal zone at the eastward point of the flight.  We entered the frontal zone of transition at 1000 ft, but apparently did not extend completely into the warm air. The character of the clouds changed and the winds decreased to ~ 6 kt. However, the wind directions did not shift in the appropriate way, i.e., they remained westerly.