2C: KORUS-AQ Instrumentation

ACOM instrumentation was deployed during the Korea-US Air Quality (KORUS-AQ) airborne study based in Seoul, South Korea in May-June, 2016. ACOM scientists Weinheimer and Montzka measured NO, NO2, NOy and O3, and Hall and Ullmann derived photolysis rates from measured actinic flux. The project was a joint collaboration between NASA and the National Institute of Environmental Research of Korea to investigate air quality factors and sources on the peninsula and improve the capability of satellite remote sensing of air quality for both the Korean geostationary satellite GEMS, as well as future geostationary satellites over North America. Models for air quality forecasting and analysis are also being evaluated and improved with these observations. The team included an array of government and university scientists from both countries.

Final calibrations and quality control measures were applied to the data prior to submittal to the publicly available archive at https://www-air.larc.nasa.gov/missions/korus-aq. A Rapid Science Synthesis Report was provided to the South Korean Ministry of Environment to allow immediate actions to be considered to mitigate air quality issues at https://espo.nasa.gov/korus-aq while more comprehensive analysis will continue from the dataset.

Among the objectives of KORUS-AQ was the determination of emissions from various pollution sources on the Korean Peninsula.  One of the prominent sources of active nitrogen oxides (NOx = NO + NO2) are power plants, and these are well suited for sampling via aircraft.  NOx is essential to the production of O3.  Figure 1 shows measurements of NOx and O3 made while circling a plant at close range.  Extremely large NOx values, exceeding 50 ppbv, were observed.  Additionally, there was a significant impact on O3 mixing ratios on this short time scale.  These measurements, along with measurements of the overall levels of NOx throughout the peninsula, are being compared with the levels of NOx generated in model runs.  This will enable an assessment of the emission scenarios incorporated into the models as well as the model photochemistry, work which is being pursued vigorously within ACOM (please also see 3C KORUS-AQ).

Figure 1
Figure 1.

Another objective of the mission was to determine the photochemical evolution of pollutants within and beyond the Seoul Metropolitan Area (SMA).  Figure 2 shows the NASA DC-8 (left) taking off in heavily aerosol-laden conditions. A vertical profile near Seoul (right) shows the ratio of measured NO2 photolysis frequency (jNO2) to the cloud-free NCAR Tropospheric Ultraviolet and Visible (TUV). Strong ultraviolet absorption by the aerosols is most pronounced near the surface where jNO2 is suppressed by up to 30%. Such reductions inhibit the local photochemical evolution of pollutants, including ozone production over the Seoul metropolitan area. Thus some air quality impacts are deferred to downstream rural and regional locations where pollutants further interact with biogenic, oceanic and additional anthropogenic emissions.

Figure 2
Figure 2.