Abstract: The aerosols in Shanghai during winter and spring generally exhibited scattering-dominated characteristics, although significant additional absorption was observed in the shortwave band. The Absorption ?ngstr?m Exponent (AAE) presented a spectral distribution of AAE370-520 nm > AAE370-880 nm > AAE520-880 nm, confirming the continuous presence of brown carbon (BrC) in the regional atmosphere. The segregated black carbon (BC) absorption showed a higher correlation with BC mass concentration, indicating that the improved AAE algorithm can effectively separate BC and BrC absorption. During the observation period, both scattering and absorption coefficients demonstrated distinct diurnal variations, which were primarily co-controlled by traffic emissions and boundary layer evolution. The relative contribution of BrC absorption increased in the afternoon, reflecting the promotion of secondary organic chromophore formation by photochemical processes. Total extinction analysis indicated that the accumulation of secondary inorganic salts was the dominant factor driving visibility deterioration during heavy winter pollution, whereas the rapid scavenging of scattering components in spring led to an enhanced relative absorption contribution of BC. Further analysis revealed that under high AAE conditions, the mass absorption cross-section (MAC) of BrC decreased significantly in the afternoon, demonstrating typical photobleaching characteristics. However, the MAC of BC remained relatively stable in both seasons, and no consistent diurnal enhancement was observed across different AAE groups. This suggests that the absorption enhancement of BC is not solely influenced by secondary component coatings, but is mutually constrained by complex factors including the degree of particle aging, coating structure, and boundary layer evolution.