The Megacity Air Pollution Studies-Seoul (MAPS-Seoul) 2015 Campaign was conducted during 27 May–13 June 2015 as a pilot for the Korea-US Air Quality (KORUS-AQ) 2016 campaign, and seven flights were conducted around the west coast of Korean Peninsula, Yellow Sea, Seoul metropolitan area, and several urban/suburban areas in South Korea. During the MAPS-Seoul 2015 Campaign period, signatures of long-range transport processes over Northeast Asia were summarized from the following: 1) the presentation of a brief description of the synoptic situations for each of the seven flight missions from RF1 to RF7, 2) interpretations of both streamline and trajectory analyses to describe the meteorological history of an air mass, and 3) a total of 17 meteorological parameters, including geostrophic wind speed, vorticity at a geopotential height of 850 hPa, and several vertical stability indices were employed and used to determine the characteristics of the long-range transport process.
The synoptic conditions during the campaign period were characterized by the migratory cyclone and anticyclones with appropriate streamlines and backward trajectories over Northeast Asia. The “stagnant” case was characterized by weak geostrophic wind speed, smaller vorticity, and lower humidity atmospheric conditions, whereas the “long-range transport” case had stronger geostrophic wind speed, positive vorticity, and higher humidity atmospheric conditions. Among the seven flights (RF1 to RF7), RF1 and RF2 identified as dominant stagnant synoptic cases from several diagnostic variables, while RF3, RF6, and RF7 observed long-range transport processes. RF4 found two mixed characteristics: upper atmosphere with long-range transport processes and lower atmosphere characterized by stagnant conditions, and RF5 showed the transport pattern from the South marine atmosphere without long-range transport processes from the high emission area. Other meteorological features were also discussed in association with the signatures of the long-range transport processes experienced over Northeast Asia during the MAPS-Seoul 2015 Campaign period.