Take-off time 9:12 am local (0012Z); flight duration 7.5 hours  

Title: Warm conveyor belt and cyclonic recirculation  Objectives: (1) to examine the "wrap-around" recirculation around a kamikaze cyclonic bomb NE of Japan; (2) to sample the warm conveyor belt ahead of a newer front pushed east from Japan (and responsible for snow over Yokota that morning); (3) to provide DIAL support to the ACE-Asia Twin Otter radiation experiment over the Sea of Japan north of Iwakuni.  

Execution: The flight track was a "box" around Honshu and Hokkaido.  We headed W to (35N, 131E) to overfly the Twin Otter on their wall between (35.5N, 131.8E) and (35.7N, 131.7E) at 0135-0138Z.  We then headed NE to the northern tip of Hokkaido at (45N, 141E) followed by a SE leg to (39N, 150E) to sample the wrap-around circulation around the kamikaze cyclonic bomb that had been sitting to the NE of Hokkaido for the past few days. From there we flew SW to Yokota (36N, 139E), sampling the rising air along the warm conveyor belt pushed east of Japan.  

Results: We met our objectives and sampled complicated chemical signatures associated with the warm conveyor belt and the cyclonic recirculation. Climbing out of Yokota we saw considerable fine structure below 10Kft associated with lifting of Japanese pollution by the front sitting over the area at the time, and coarser pollution structure above interwoven with stratospheric filaments (recirculation around the kamikaze?).  The 31Kft leg to Iwakuni was in and out of the stratosphere.  The Twin Otter overfly was conducted in a clear patch in a broken cloud field with good functioning of the DIAL.  Heading NE over the Sea of Japan, we observed a depressed tropopause at 18Kft (jet stream), complicated pollution influences just below (the recirculation?)  and direct Korean outflow below 10Kft with everything elevated (200-250 ppbv CO).  As we approached the northern tip of Hokkaido the tropopause rose, and we sampled extensive aged (?) pollution at all altitudes (CO 150-200 ppbv, high PAN, C₂Cl₄, nitriles, moderately high SO₂, HCHO, ).  Heading back SE and then SW we observed a range of Asian outflow layers at all levels with different chemical signatures. The recirculating pollution in the north showed moderately high CO (150-200 ppb), high C₂Cl₄, PAN, nitriles, low HCHO, and was interleaved with stratospheric filaments.  The warm conveyor belt further south showed higher CO (up to 300 ppb).  NO was very low in the "recirculating pollution" (< 10 pptv) but had a lot of structure with values in excess of 100 pptv in the warm conveyor belt associated with recent convection (high CH₃OOH/H₂O₂ ratios).  The NO structure was probably associated at least in part with lightning.

Flow Features:

         Surface--A major low pressure area was centered near 47N 158E. With a central pressure of ~974 mb, this system previously had reached "bomb" status.  A developing low pressure area was moving up the eastern coast of Japan.  Although its central pressure was only ~1004 mb, it produced widespread light snow and rain over eastern Japan during the entire day.  The cold front extending south of the low reinforced the cold air already in place over Japan.  A high pressure area was located near Shanghai.
         Middle troposphere-The major closed cyclonic circulation was nearly vertically stacked with its surface counterpart described above (47N 158E).  A short wave trof extending southwest of this system was associated with the developing surface system.
         Upper troposphere-The closed cyclone continued, with an additional cyclonic center located just west of northern Japan.  This system was merely a trof at lower levels.  It produced light southerly winds along the northern part of the flight track (an unexpected occurrence).  The axis of the jet stream stretched from just south of Japan toward the east-northeast. The jet was quite intense, with strongest winds (~ 170 kt) located near 38N, 160E. Speeds near 100 kt were even as low as 500 mb.

Cloud Features and Other Goodies:

         The major cloud feature was a classic "comma" shaped pattern associated with the developing low skirting the east coast of Japan. Clouds at all levels were occurring in this area.  The Stormscope indicated a few lightning flashes east of Japan in the area of the developing low.  However, these flashes were few in number.
         The area of the Twin Otter overpass was mostly cloudy with middle and upper level clouds.  However, some breaks were present, and the two aircraft took maximum advantage of this fortuitous event.
Stratospheric air was encountered during the southwestern part of the flight track. This region was in the left entrance region of the jet streak described above.