Flight summary, DC-8 flight 14 - Yokota local 2   -  03/24/2001. 

Take-off time 8:20 am local (2320Z on 0321); flight duration 9.0 hours  

Title: Convective outflow  Objectives: (1)  to sample high-altitude outflow from intense convective activity developing over SE Asia, China, and the western Pacific; (2) to conduct a high-altitude intercomparison with the P-3, (3) to conduct a MOPITT validation experiment.  

Execution: The intercomparison between the two aircraft consisted of a level leg at 17Kft with the two planes flying in parallel (2000' apart) for 30 minutes.  This leg was conducted upon take-off from Yokota along a (33N, 137-140E) track.  We then flew SE to (24N, 150E) for a MOPITT underpass spiral from 35 to 0.5Kft and to sample expected convective outflow.  From there we flew SW to (21N, 140E)  and then NW to (26N, 135E) where we headed N, downstream of a thunderstorm developing to our W.  We conducted a spiral up at (29N, 135E) to sample outflow from the storm but were restricted to 27Kft by ATC.   We were able to climb to 33Kft at (31N, 135E) and from there headed to Yokota with a slow in-progress descent. 

Results: The objectives were met and the flight yielded several surprises. The intercomparison was a success: both aircraft managed to operate at the same speed, air was dry, and skies were clear.  There was quite a bit of structure in ozone, anticorrelated with H2O (stratospheric influence?), and a transition in air mass was seen over the course of the intercomparison leg.  On the leg SE toward the MOPITT underpass we sampled structures indicative of stratospheric filaments, aged Asian outflow in the lower free troposphere, and deep convective outflow.  At 35Kft at the MOPITT underpass point we found the strongest pollution influence sampled so far in the mission in the upper troposphere (CO  200 ppbv with O3  80 ppbv, HCHO 200 pptv).  This pollution reflected a combination of industrial and biomass burning influences (high C2Cl4, high CH3CN) and appeared from satellite imagery to originate from deep convection over eastern China.  The MOPITT underpass spiral was conducted under clear skies with high-CO layers at 35Kft, 7 Kft, and 12 Kft.  In the boundary layer at (24N, 150E) there was a surprising level of pollution influence (O3 50 ppbv, CO 140 ppbv).  Climb to 29 Kft at 21N indicated again high levels of pollution associated with convective outflow, presumably over eastern China.  Further vertical profiling on the way back to Yokota indicated surprisingly high levels of pollution at all levels, with CO frequently above 200 ppbv.  

Meteorological Summary DC-8 Yokota Local # 2  24 March 2001


Relevant Flow Features
         Surface-Several weak low pressure areas were relevant to the flight.  The strongest was over extreme northern Japan, while weaker lows were centered over the northwestern Yellow Sea and over southeastern China (northwest of Taiwan).  A weak anticyclone was over central Japan. Surface flow over much of the flight track was from the east or northeast.

         Middle troposphere-A closed cyclone was just north of Japan. Westerly flow covered all of the flight track.

         Upper troposphere-The polar jet stream continued to be poorly defined at 300 mb.  However, the subtropical jet stream was well defined at 200 hPa, with its axis over the flight track along ~30N.  However, unlike most previous flights, strongest winds were not near Japan. Instead, one jet streak was over eastern China, while a second stretched over Saudi Arabia and northwestern India.  Maximum jet stream speeds appear to have weakened since the start of TRACE-P. Westerly winds were over the entire flight area.

Relevant Cloud Features
         An area of deep convection formed over eastern China the previous day. It was the biggest area of Asian convection seen thus far.  The area moved eastward into the western Pacific during the night. By 2030Z on the flight day, the storm complex was near 28N, 128E.  Water vapor imagery revealed a plume of vapor extending eastward from the storms, remaining evident as far as 148E.  The storm area moved southeastward during the flight.  At 0700Z the storms extended along 134E from 23-26N.  A second area of deep convection formed during the day near these same latitudes but between 140-147E.  For the first time during TRACE-P, the Stormscope detected a number of lightning flashes.

Clouds conditions near the DC-8 - P-3 rendezvous were ideal. Only small scattered cumulus and thin scattered cirrus were observed.  Ideal cloud conditions also covered the MOPITT underpass area.  Isolated small cumulus had bases near 2800 ft and tops near 4800 ft.  A few thin cirrus strands were along the northern portion of the spiral area.  However, they did not appear to be directly overhead at any time.

         The second boundary layer run (near 0440Z) had scattered cumulus with bases near 2,200 ft and most tops near 3,000 ft (although a few tops reached 5,000 ft). On the other hand, the third boundary layer run (near 0546Z) was characterized by an overcast layer of multiple layered clouds. Rain occurred during part of this run. During the ascent, the main cloud layers had tops of ~19,000 ft.  However, broken cirrus was at even higher altitudes.