Seasonal variation of C2–C6 NMHCs at Happo, a remote site in Japan

The measurement for 1 year from March 1998–February 1999 was achieved for 28 non-methane hydrocarbons (NMHC) at a remote site, Happo, Japan (137°48′E longitude and 36°41′N latitude). The mixing ratio of NMHC showed well-defined seasonal cycle with winter maximum and summer minimum for ethane, propane, C4–C5 alkanes, n-hexane and acetylene consistent with the seasonal variation of OH radical. Ethene and propene did not show clear seasonal cycle. The trajectory analyses showed that NMHC in the Pacific rim region at remote site is affected by anthropogenic emission from the Asian continent. Comparison of the seasonal cycle revealed that higher latitude exceeded the concentration for C2–C5 alkanes than mid-latitude in the northeren hemisphere.