Quantifying daily NOx and CO2 emissions from Wuhan using satellite observations from TROPOMI and OCO-2
- 1Wageningen University, Environmental Science Group, Wageningen, the Netherlands
- 2Key Laboratory of Radiometric Calibration and Validation for Environmental Satellites, Innovation Center for Fengyun Meteorological Satellite (FYSIC), National Satellite Meteorological Center, China Meteorology Administration, Beijing, 100081, China
- 3Royal Netherlands Meteorological Institute, De Bilt, the Netherlands
- 4State Key Joint Laboratory of Environmental Simulation and Pollution Control, School of environment, Tsinghua University, Beijing 100084, China
- 5Satellite Application Center for Ecology and Environment, Ministry of Ecology and Environment of the People's Republic of China, Beijing, 100094, China
- 1Wageningen University, Environmental Science Group, Wageningen, the Netherlands
- 2Key Laboratory of Radiometric Calibration and Validation for Environmental Satellites, Innovation Center for Fengyun Meteorological Satellite (FYSIC), National Satellite Meteorological Center, China Meteorology Administration, Beijing, 100081, China
- 3Royal Netherlands Meteorological Institute, De Bilt, the Netherlands
- 4State Key Joint Laboratory of Environmental Simulation and Pollution Control, School of environment, Tsinghua University, Beijing 100084, China
- 5Satellite Application Center for Ecology and Environment, Ministry of Ecology and Environment of the People's Republic of China, Beijing, 100094, China
Abstract. Quantification and control of NOx and CO2 emissions are important across the world to limit adverse climate change. We present a new top-down method, an improved superposition column model to estimate day-to-day NOx and CO2 emissions from the large city of Wuhan, China, located in a polluted background. The lasted released version 2.3.1 TROPOMI NO2 columns and the version 10r of the OCO-2 observed CO2 mixing ratio are employed. Our estimated NOx and CO2 emissions from Wuhan are verified against bottom-up inventories with small deviations (< 3 %). Based on the estimated CO2 emissions, we also predicted daily CO2 column mixing ratio enhancements, which match well with OCO-2 observations (< 5 % bias, within ±0.3 ppm). We capture the day-to-day variation of NOx and CO2 emissions from Wuhan in 2019–2020, which does not reveal a substantial ‘weekend reduction’ but does show a clear ‘holiday reduction’ in the NOx and CO2 emissions. Our method also quantifies the abrupt decrease and slow rebound of NOx and CO2 emissions due to the Wuhan lockdown in early 2020. This work demonstrates the improved superposition model to be a promising new tool for the quantification of city NOx and CO2 emissions, allowing policy makers to gain real-time information into spatial-temporal emission patterns and the effectiveness of carbon and nitrogen regulation in urban environments.
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Qianqian Zhang et al.
Interactive discussion
Status: closed
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RC1: 'Comment on acp-2022-579', Anonymous Referee #1, 20 Sep 2022
This manuscript investigated NOx and CO2 emissions at a high spatial and temporal resolution based on an improved method. It provides insights into the real-time and detailed emission quantification and control of NOx and CO2. This study is well organized and developed. I thinks this work is interesting from a scientific point of view.
Some revisions are suggested below to improve the quality of the manuscript:
- Only the photochemical loss of NO2 is considered in the establishment of the superposition column model, how does the other pathways of NO2 loss? Are they also play a role in NOx chemistry?
- It is not clear to me how the ‘starting background NO2 value’ is determined.
- In line 140-145, the authors say that the negative α value reflects the decay of upwind NO2 pollution along the wind, how come there are still positive α values?
- The study obtains only 50 out of 365 days of valid data to quantify the NOx and CO2 emissions, isn’t it too few to estimate the daily variation of NOx and CO2 emissions?
- Is there a difference in the overpass time of the TROPOMI and OCO-2 satellites? And how is this considered in the study?
- According to Fig. S1, the predicted NOx emission pattern is ‘smoother’ compared to the bottom-up emissions, do the authors think about the reason?
- S4 shows that when the study domain is smaller, the estimated NOx lifetime is longer, how come?
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- AC1: 'Reply on RC1', Qianqian Zhang, 03 Nov 2022
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RC2: 'Comment on acp-2022-579', Anonymous Referee #2, 16 Oct 2022
The comment was uploaded in the form of a supplement: https://acp.copernicus.org/preprints/acp-2022-579/acp-2022-579-RC2-supplement.pdf
- AC2: 'Reply on RC2', Qianqian Zhang, 03 Nov 2022
Peer review completion




Interactive discussion
Status: closed
-
RC1: 'Comment on acp-2022-579', Anonymous Referee #1, 20 Sep 2022
This manuscript investigated NOx and CO2 emissions at a high spatial and temporal resolution based on an improved method. It provides insights into the real-time and detailed emission quantification and control of NOx and CO2. This study is well organized and developed. I thinks this work is interesting from a scientific point of view.
Some revisions are suggested below to improve the quality of the manuscript:
- Only the photochemical loss of NO2 is considered in the establishment of the superposition column model, how does the other pathways of NO2 loss? Are they also play a role in NOx chemistry?
- It is not clear to me how the ‘starting background NO2 value’ is determined.
- In line 140-145, the authors say that the negative α value reflects the decay of upwind NO2 pollution along the wind, how come there are still positive α values?
- The study obtains only 50 out of 365 days of valid data to quantify the NOx and CO2 emissions, isn’t it too few to estimate the daily variation of NOx and CO2 emissions?
- Is there a difference in the overpass time of the TROPOMI and OCO-2 satellites? And how is this considered in the study?
- According to Fig. S1, the predicted NOx emission pattern is ‘smoother’ compared to the bottom-up emissions, do the authors think about the reason?
- S4 shows that when the study domain is smaller, the estimated NOx lifetime is longer, how come?
Â
Â
- AC1: 'Reply on RC1', Qianqian Zhang, 03 Nov 2022
-
RC2: 'Comment on acp-2022-579', Anonymous Referee #2, 16 Oct 2022
The comment was uploaded in the form of a supplement: https://acp.copernicus.org/preprints/acp-2022-579/acp-2022-579-RC2-supplement.pdf
- AC2: 'Reply on RC2', Qianqian Zhang, 03 Nov 2022
Peer review completion




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Qianqian Zhang et al.
Qianqian Zhang et al.
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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