The observations conducted at SORPES station to study the formation of particulate nitrate in residual layer

The common nitrate-driven aerosol pollution renders reduction of nitrate as a high priority for air quality improvement. However, the significant vertical heterogeneity of nitrate and its precursors limits our understanding of its formation. By combining airship and long-term ground measurements with model simulations, the nitrate-driven pollution was found to be caused by the hydrolysis of N2O5 in residual layer (RL) favored by high O3