Increasing contribution of nighttime nitrogen chemistry to wintertime haze formation in Beijing observed during COVID-19 lockdowns

Chao Yan, Yee Jun Tham, Wei Nie, Men Xia, Haichao Wang, Yishuo Guo, Wei Ma, Junlei Zhan, Chenjie Hua, Yuanyuan Li, Chenjuan Deng, Yiran Li, Feixue Zheng, Xin Chen, Qinyi Li, Gen Zhang, Anoop S. Mahajan, Carlos A. Cuevas, Dan Dan Huang, Zhe Wang, Yele Sun, Alfonso Saiz‐Lopez, Federico Bianchi, Veli‐Matti Kerminen, Douglas R. Worsnop, Neil M. Donahue, Jingkun Jiang, Yongchun Liu, Aijun Ding, Markku Kulmala