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