Flight summary, DC-8 flight 13 - Yokota local 1   -  03/21/2001. 

Take-off time 8:20 am local (2320 Z on 0320); flight duration 9.4 hours  

Title: Frontal lifting and dust outflow  

Objectives: (1)  to characterize the lifting of Asian outflow by a cold front, (2) to sample convective outflow from SE Asia in the upper troposphere (3) to sample dust and pollution outflow near the China coast, (4) to sample the stratosphere subsiding on the north side of the jet stream, (5) to conduct a MOPITT validation experiment in background tropical air.  

Execution: We flew from Yokota (36N, 139E) SW to cross an active cold front (vertical profiling) and conducted a MOPITT validation spiral from 35 to 0.5 Kft at (22N, 130E).  We then flew NW to (30N, 125E), re-crossing the front with vertical profiling, and conducted a N return leg into the Yellow Sea to (35N, 125E) to sample dust and pollution outflow.  From there we climbed to cruise altitude and returned to Yokota.  

Results: All objectives were met.  On the climb up from Yokota we sampled the "high-ozone layer" (90 ppbv O3, flat CO, depressed CO₂, high HCHO, PAN, nitriles) which appears to originate from aged biomass burning (although exact origin is still a mystery).  Fresher biomass burning outflow, most likely of SE Asian origin, was sampled at 31Kft on the SW leg from Yokota to (22N, 130E).  Crossing of the front at (36N, 136E) was conducted under particularly active conditions below 10Kft, with considerable structure in the frontal cloud outflow reflecting fresh lifting of Asian pollution (high CH3OOH/H2O2 ratio, high C2Cl4, high nitriles, considerable fine structure in CO, CO₂, CH₄, N₂O).  Continuing SW, as we got in the boundary layer at 1Kft we returned on the cold side of the front (CO over 300 ppbv, acetone over 1 ppbv).  This boundary layer outflow was capped at 5Kft, as seen in previous flights; above that altitude we were on the warm side of the front with clean air and little structure.  Our MOPITT spiral (delayed 30 min because of ATC) was conducted in a relatively featureless atmosphere with only a modest boundary layer enhancement of CO.  On our flight NW we re-crossed the front at 26N, sampling lifted Asian pollution at 12 Kft (CO up to 210 ppb, CO₂ above 382 ppmv), and we then hit considerable Asian pollution behind the front heading north in the boundary layer, including in particular a well-defined crossing of the Shangai plume at 30N (CO up to 1240 ppbv, O3 up to 140 ppbv, HCHO 8 ppbv, Acetone 6 ppbv, HCN 2 ppbv, PAN 6 ppbv, high SO₂, CH₄ up 10-15%, etc).  There was strong evidence of dust associated with this plume (yellow aerosol filters!).  The pollution was capped at 5Kft by a dry subsiding air mass with low CO.  Heading further north into the Yellow Sea we identified dust layers mixed with pollution using the DIAL depolarization signal and conducted boundary layer sampling in a mixture of pollution and dust.  The dust-pollution mix was in contrast to the "clean" dust layer sampled on the Okinawa-Yokota transit.  Climibing up on our return leg from the Yellow Sea we entered the stratosphere at 29Kft and stayed there for most of our return to Yokota.  

Meteorological Summary  DC-8 Yokota Local Number 1  Henry Fuelberg

Relevant Flow Patterns
         Surface-A low pressure area was centered over extreme northern Japan. A cold front extended from it-first toward the southeast along 150E, and then southwest toward Taiwan.  The surface high pressure behind the front was relatively small.  A developing low pressure area was located over northeastern Asia.

         Middle Troposphere-A closed low was located just north of Japan. It was the middle level reflection of the surface cyclone described above. The subtropical high was located near 19N, 140E.  Westerly flow dominated the flight track.

         Upper troposphere-The subtropical jet stream was oriented just south of Japan. Strongest speeds (the jet streak) stretched from east to west from south of Tokyo to near Okinawa.  Westerly winds covered the entire flight track.

Relevant Cloud Patterns
         The overall pattern was a band of middle and upper clouds stretching from south of Tokyo to near Hong Kong.  The cloud band was widest just south of Tokyo and quite narrow on its southwestern edge.  Low level clouds covered much of the flight track.  Details area given below.

         First boundary layer run-The DC-8 penetrated the frontal zone from above at an altitude of ~5,000 ft.  Winds below were from the northwest, and from the west above.  Rain was encountered in the area.  Considerable turbulence was encountered due to the convective nature of the clouds.  We apparently did not pass into the warm air while at 2,000 ft, but were close to the leading edge of the front

MOPITT area-Only scattered cumulus were in the area.  Bases were near 1500 ft, and tops near 5,000 ft. Some cirrus were south of the cloud track.  Due to ATC problems, the DC-8 had to circle the area before descending.  Contrails were created during this time.

         The DC-8 crossed the surface position of the front a second time as it headed northward along the western portion of the flight track