Retrieval of the Vertical Profiles of Aerosols, HONO, and Ozone in Kunming’s Winter and Their Interrelationships Based on the MAX-DOAS

This study adopts MAX-DOAS technology and optimal estimation methods to analyze the vertical profiles of aerosols, HONO, and O3 in Kunming during winter 2024, thereby clarifying their vertical distribution characteristics and diurnal variation rules. Aerosols are predominantly concentrated in the near-surface layer, with concentrations decreasing gradually with increasing altitude; their concentrations rise in the morning, reach a peak at 10 a.m., and then decline, with the maximum extinction coefficient reaching 1.3 km−1. HONO concentrations decrease exponentially with height, being the highest around sunrise, the lowest at noon, and then gradually accumulating, with the maximum concentration exceeding 3.14 × 1010 molec·cm−3. O3 achieves its maximum concentration in the 2.6–4 km altitude range in the afternoon (the highest concentration > 1.16 × 1012 molec·cm−3), while near-surface O3 concentrations increase steadily from morning onward. Model analysis demonstrates that without considering HONO, OH radicals shift from net production to net loss in the morning, leading to reduced O3 production rates and a decrease of approximately 8 ppb in the maximum O3 concentration. These findings highlight the significant vertical and diurnal variations in the three pollutants, emphasize HONO’s crucial role in OH radical generation and O3 formation, provide valuable scientific support for air pollution control, and confirm HONO’s important impact on regional atmospheric chemistry and the distribution of key pollutants.