Abstract. The black carbon (BC) and carbon monoxide (CO) emission ratios were
estimated and compiled from long-term, harmonized observations of the
ΔBC∕ΔCO ratios under conditions unaffected by wet deposition
at four sites in East Asia, including two sites in South Korea (Baengnyeong and
Gosan) and two sites in Japan (Noto and Fukuoka). Extended spatio-temporal
coverage enabled estimation of the full seasonality and elucidation of the
emission ratio in North Korea for the first time. The estimated ratios were
used to validate the Regional Emission inventory in ASia (REAS) version 2.1
based on six study domains (“East China”, “North China”, “Northeast China”, South
Korea, North Korea, and Japan). We found that the ΔBC∕ΔCO
ratios from four sites converged into a narrow range (6.2–7.9 ng m−3 ppb−1), suggesting consistency in the results from independent
observations and similarity in source profiles over the regions. The BC∕CO ratios from the REAS emission inventory (7.7 ng m−3 ppb−1 for East
China – 23.2 ng m−3 ppb−1 for South Korea) were overestimated by
factors of 1.1 for East China to 3.0 for South Korea, whereas the ratio for
North Korea (3.7 ng m−3 ppb−1 from REAS) was underestimated by a
factor of 2.0, most likely due to inaccurate emissions from the road
transportation sector. Seasonal variation in the BC∕CO ratio from REAS was
found to be the highest in winter (China and North Korea) or summer (South
Korea and Japan), whereas the measured ΔBC∕ΔCO ratio was the
highest in spring in all source regions, indicating the need for further
characterization of the seasonality when creating a bottom-up emission
inventory. At levels of administrative districts, overestimation in Seoul,
the southwestern regions of South Korea, and Northeast China was noticeable,
and underestimation was mainly observed in the western regions in North
Korea, including Pyongyang. These diagnoses are useful for identifying
regions where revisions in the inventory are necessary, providing guidance
for the refinement of BC and CO emission rate estimates over East Asia.
Regional variability in black carbon and carbon monoxide ratio from long-term observations over East Asia: assessment of representativeness for black carbon (BC) and carbon monoxide (CO) emission inventories