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Monthly mean seasonal cycle of TCNO2 in Upper West Manhattan pre-lockdown (December 2017–December 2019, cyan) and post-lockdown (April 2020–December 2020, blue, and January–May 2021, red), as measured by PSI #135 (30min averaged data; 95% confidence intervals indicated by error bars; data not available during January–March 2020). The percentage (%) change is also shown below each bar.
