Why is the Indo-Gangetic Plain the region with the largest NH3 column in the globe during pre-monsoon and monsoon seasons? - Wang, T.; Song, Y.; Xu, Z.; Liu, M.; Xu, T.; Liao, W.; Yin, L.; Cai, X.; Kang, L.; Zhang, H.; Zhu, T. (Atmos. Chem. Phys., 2020)