CFCs measurements at high altitudes in northern China during 2017–2018: Concentrations and potential emission source regions

Constraining Emission Estimates of CFC-11 in Eastern China Based on Local Observations at Surface Stations and Mount Tai

“…At the island site TJI, CFC-11 mixing ratios observed in December 2014 ranged from 230 to 290 ppt with an average of 245 ± 15 ppt, ∼5% above that at MLO. At the MT site, mixing ratios of CFC-11 ranged from 234 to 360 ppt with an average of 267 ± 22 ppt (∼15% above that at MLO) during summer 2014 and ranged from 230 to 279 ppt with an average of 249 ± 13 ppt (∼7% above that at MLO) from winter 2017 to spring 2018, consistent with the average of 257 ppt from June 2017 to April 2018 at the same MT site as reported by Yang et al 24 The mixing ratios of CFC-11 as high as 360 ppt at the MT site in this study also indicated occasionally there might be extensive CFC-11 emissions.…”

Airborne Observations of CFCs Over Hebei Province, China in Spring 2016

“…M. Yang et al. (2021) also used the PSCF method to find high CFC‐11 mixing ratios observed from June 2017‐April 2018 at Mount Tai (located in Shandong Province) had traveled from Shanxi, Hebei, Anhui, and Henan provinces. Rigby et al.…”

“…Here, n ij is the total number of endpoints that fall in the ijth cell (Figure ) and m ij is the number of endpoints for which measured values exceed a specified criterion value in the ijth cell. Previous studies used the mean (Hui et al., 2019; Lin et al., 2019), 50th percentile (Li, Ye, et al., 2016; Polissar et al., 1999), 75th percentile (N. Gao et al., 2012; M. Yang et al., 2021; Zhao et al., 2015), and 90th percentile (Cheng & Lin, 2001; Fang et al., 2018) as criterion values. In this study, criterion values were selected based on the mean, 50th percentile, 75th percentile, and 90th percentile of measured CFC‐11 data to identify potential emission source regions of higher CFC‐11 mixing ratios (Figure ).…”

“…Here, n ij is the total number of endpoints that fall in the ijth cell (Figure S2) and m ij is the number of endpoints for which measured values exceed a specified criterion value in the ijth cell. Previous studies used the mean (Hui et al, 2019;Lin et al, 2019), 50th percentile (Li, Ye, et al, 2016;Polissar et al, 1999), 75th percentile (N. Gao et al, 2012;M. Yang et al, 2021;Zhao et al, 2015), and 90th percentile Fang et al, 2018) as criterion values.…”

“…Also applying the PSCF technique, Lin et al (2019) documented that high levels of CFC-11 observed in Nanjing, China in October 2017 originated from less developed regions in southwestern and central China, with a minor fraction emerging from the PRD metropolitan region. M. Yang et al (2021) also used the PSCF method to find high CFC-11 mixing ratios observed from June 2017-April 2018 at Mount Tai (located in Shandong Province) had traveled from Shanxi, Hebei, Anhui, and Henan provinces. Rigby et al (2019) used chemical transport model simulations joined with CFC-11 observations in Gosan, South Korea and Hateruma, Japan to identify Shandong and Hebei Provinces as partly responsible for the global rise in CFC-11 emissions.…”