Ground-Level NO2 Surveillance from Space Across China for High Resolution Using Interpretable Spatiotemporally Weighted Artificial Intelligence

Nitrogen dioxide (NO2) at the ground level poses a serious threat to environmental quality and public health. This study developed a novel, artificial intelligence approach by integrating spatiotemporally weighted information into the missing extra-trees and deep forest models to first fill the satellite data gaps and increase data availability by 49% and then derive daily 1 km surface NO2 concentrations over mainland China with full spatial coverage (100%) for the period 2019-2020 by combining surface NO2 measurements, satellite tropospheric NO2 columns derived from TROPOMI and OMI, atmospheric reanalysis, and model simulations. Our daily surface NO2 estimates have an average out-of-sample (out-of-city) cross-validation coefficient of determination of 0.93 (0.71) and root-mean-square error of 4.89 (9.95) μg/m3. The daily seamless high-resolution and high-quality dataset "ChinaHighNO2"allows us to examine spatial patterns at fine scales such as the urban-rural contrast. We observed systematic large differences between urban and rural areas (28% on average) in surface NO2, especially in provincial capitals. Strong holiday effects were found, with average declines of 22 and 14% during the Spring Festival and the National Day in China, respectively. Unlike North America and Europe, there is little difference between weekdays and weekends (within ±1 μg/m3). During the COVID-19 pandemic, surface NO2 concentrations decreased considerably and then gradually returned to normal levels around the 72nd day after the Lunar New Year in China, which is about 3 weeks longer than the tropospheric NO2 column, implying that the former can better represent the changes in NOx emissions.

Bibliographic Details

Main Authors:	Wei, Jing, Liu, Song, Li, Zhanqing, Liu, Cheng, Qin, Kai, Liu, Xiong, Pinker, Rachel T., Dickerson, Russell R., Lin, Jintai, Boersma, K.F., Sun, Lin, Li, Runze, Xue, Wenhao, Cui, Yuanzheng, Zhang, Chengxin, Wang, Jun
Format:	Article/Letter to editor biblioteca
Language:	English
Subjects:	COVID-19, air pollution, artificial intelligence, big data, surface NO,
Online Access:	https://research.wur.nl/en/publications/ground-level-nosub2sub-surveillance-from-space-across-china-for-h
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