Using Short‐Term CO/CO₂ Ratios to Assess Air Mass Differences Over the Korean Peninsula During KORUS‐AQ

Abstract

One‐second in situ measurements of CO and CO2 mole fractions were made aboard the National Aeronautics and Space Administration DC‐8 aircraft during the 2016 KORUS‐AQ joint air quality and atmospheric chemistry field campaign in South Korea. The ratio of CO to CO2 enhancement is used to characterize regional combustion source signatures. Calculations of the ∆CO/∆CO2 ratio were made with a short duration rolling window (60 s), filtered by the coefficient of determination (R2), and plotted as distributions to characterize air masses measured from the aircraft during the campaign. The KORUS‐AQ sampling domain was divided into analysis regions to facilitate the analysis. Over Seoul, the boundary layer shows a low‐ratio signature in the ∆CO/∆CO2 ratios, with more than 50% of the correlated slopes in the boundary layer falling below 1% ∆CO/∆CO2, and 80% of the slopes between 0% and 2% ∆CO/∆CO2. However, this behavior changes to a larger ratio distribution at higher altitudes. The West Sea receptor region was divided into three analysis sectors, by meteorological regime, and used in conjunction with measurements collected over China during the KORUS‐AQ campaign time period to characterize the Chinese ∆CO/∆CO2 ratio signature. Chinese‐type emissions have a slope distribution that is shifted to higher ratios and broadened compared to measurements over Seoul, with the bulk of the measurements between 2% and 4% ∆CO/∆CO2, with few negative slopes. The measured ratio trends over South Korea are consistent with inventoried CO and CO2 emissions.

Measurement Report: Aircraft Observations of Ozone, Nitrogen Oxides, and Volatile Organic Compounds over Hebei Province, China

“…5a) shows high linear correlation (R=0.90) and high ratios of CO/CO2 (2.4%) together with large amounts of SO2. These measurements are indicative of low-efficiency fossil fuel combustion, likely from residential coal burning as these observations were all collected at ~500 m. These results agree with airborne data from the KORUS-AQ campaign during Chinese-sourced inflow indicating 1-4% CO/CO2 (attributing to low-efficiency combustion) (Halliday et al, 2019). Similarly, Xia et al (2020) found higher CO/CO2 ratios ~2% in December 2017 at Jingdezhen station in central China when air mass transport was from northern China, although they note some high combustion efficiency may be found in Jiangxi and Hunan provinces in Central China.…”

“…This work was supported by National Science Foundation (NSF 9188-1524) * Statistics calculated for 1-second data during three flights at all altitudes during the "extreme pollution period" (Choi et al, 2019) where the KORUS-AQ DC-8 flew over the Yellow Sea to measure outflow from China. a Yang et al, (2016).…”

Investigation of factors controlling PM2.5 variability across the South Korean Peninsula during KORUS-AQ

“…To further examine the role of transboundary transport during the KORUS-AQ study, a metric based on the covariance of CO and CO 2 observations from the DC-8 is shown along with the time series of the hourly average PM 2.5 of the Seoul City sector in Figure 6. Halliday et al (2019) developed this metric by examining slopes for high-resolution (1 Hz) Figure 6: Time series of the hourly average PM 2.5 concentrations during the KORUS-AQ period for AirKorea sites in Seoul City. Median CO/CO 2 slopes are shown for DC-8 flight days and are taken from descent profiles over Seoul.…”

“…This metric is useful for distinguishing sources of combustion in this region, since sources in China differ in their emissions profile from those in South Korea. Halliday et al (2019) provides a detailed discussion of the evidence for these differences in emissions based on both published observations as well as concurrent airborne observations conducted in China's Hebei province during the ARIAs (Air Chemistry Research in Asia) study (He et al, 2017) which are also archived with the KORUS-AQ data. To summarize the metric, higher slopes in CO/CO 2 indicate inefficient combustion, with values as high as 4% in fresh emissions from China.…”

Evaluation of Anthropogenic Emissions and Ozone Pollution in the North China Plain: Insights from the Air Chemistry Research in Asia (ARIAs) Campaign

“…emission enhancements (EEs). Through only selecting EEs that are in the PBL (below 1.5 km AGL in this study) and statistically significant (R > 0.6), the values of EEs can act as a proxy of EFs in the air mass observed (Halliday et al, 2018).…”