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. 2020 Oct 19;47(20):e2020GL090041. doi: 10.1029/2020GL090041

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©2020. American Geophysical Union. All Rights Reserved.

This article is being made freely available through PubMed Central as part of the COVID-19 public health emergency response. It can be used for unrestricted research re-use and analysis in any form or by any means with acknowledgement of the original source, for the duration of the public health emergency.

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The red dot and whisker represent the average value and standard deviation of daytime PM_2.5 during the COVID lockdown (CLD) haze event in Beijing. Based on wintertime data from 2013 to 2019, days with a similar planetary boundary layer height (PBLH), wind speed (WS), relative humidity (RH), and all three are selected (less than 20% difference). The distribution of daytime PM_2.5 is presented under these similar conditions. The black dot and whisker represent the average value and standard deviation, while the width of the color‐shaded areas represents the smoothed distribution of daytime PM_2.5. The mean PM_2.5 values for these categories are given at the top of the figure (unit: μg m⁻³).