Impacts of TROPOMI-Derived NO X Emissions on NO2 and O3 Simulations in the NCP during COVID-19

Yizhi Zhu; Cheng Liu; Qihou Hu; Jiahua Teng; Daian You; Chengxin Zhang; Jinping Ou; Ting Liu; Jinan Lin; Tianyi Xu; Xinhua Hong

doi:10.1021/acsenvironau.2c00013

Impacts of TROPOMI-Derived NO _X Emissions on NO₂ and O₃ Simulations in the NCP during COVID-19

ACS Environ Au. 2022 Jul 5;2(5):441-454. doi: 10.1021/acsenvironau.2c00013. eCollection 2022 Sep 21.

Authors

Yizhi Zhu¹, Cheng Liu^{1

2

3

4}, Qihou Hu¹, Jiahua Teng⁵, Daian You⁵, Chengxin Zhang³, Jinping Ou¹, Ting Liu⁶, Jinan Lin¹, Tianyi Xu⁷, Xinhua Hong⁷

Affiliations

¹ Key Lab of Environmental Optics & Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China.
² Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China.
³ Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei 230026, China.
⁴ Key Laboratory of Precision Scientific Instrumentation of Anhui Higher Education Institutes, University of Science and Technology of China, Hefei 230026, China.
⁵ China Satellite Application Center for Ecology and Environment, MEE, Beijing 100094, China.
⁶ School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China.
⁷ School of Environmental Science and Optoelectronic Technology, University of Science and Technology of China, Hefei 230026, China.

Abstract

NO₂ and O₃ simulations have great uncertainties during the COVID-19 epidemic, but their biases and spatial distributions can be improved with NO₂ assimilations. This study adopted two top-down NO _X inversions and estimated their impacts on NO₂ and O₃ simulation for three periods: the normal operation period (P1), the epidemic lockdown period following the Spring Festival (P2), and back to work period (P3) in the North China Plain (NCP). Two TROPOspheric Monitoring Instrument (TROPOMI) NO₂ retrievals came from the Royal Netherlands Meteorological Institute (KNMI) and the University of Science and Technology of China (USTC), respectively. Compared to the prior NO _X emissions, the two TROPOMI posteriors greatly reduced the biases between simulations with in situ measurements (NO₂ MREs: prior 85%, KNMI -27%, USTC -15%; O₃ MREs: Prior -39%, KNMI 18%, USTC 11%). The NO _X budgets from the USTC posterior were 17-31% higher than those from the KNMI one. Consequently, surface NO₂ levels constrained by USTC-TROPOMI were 9-20% higher than those by the KNMI one, and O₃ is 6-12% lower. Moreover, USTC posterior simulations showed more significant changes in adjacent periods (surface NO₂: P2 vs P1, -46%, P3 vs P2, +25%; surface O₃: P2 vs P1, +75%, P3 vs P2, +18%) than the KNMI one. For the transport flux in Beijing (BJ), the O₃ flux differed by 5-6% between the two posteriori simulations, but the difference of NO₂ flux between P2 and P3 was significant, where the USTC posterior NO₂ flux was 1.5-2 times higher than the KNMI one. Overall, our results highlight the discrepancies in NO₂ and O₃ simulations constrained by two TROPOMI products and demonstrate that the USTC posterior has lower bias in the NCP during COVD-19.