Fig. 1. Spatial distribution of BAOD in Yangtze River Delta from 2013 to 2022. The pentagram represents the location of the micro-pulse lidar (MPL) station. (BAOD statistics from MODIS data)

Fig. 2. Handling of AOD outliers (the green color represents the data range retained for calculating the mean value)

Fig. 3. Evaluation metrics of AERONET and CALIPSO AOD under different spatiotemporal matching windows.(a) Evaluation scores; (b) matched data pairs

Fig. 4. Comparison of CALIPSO AOD and AERONET AOD under a 5 km/10 min spatiotemporal matching window.(a) Scatter plot; (b) geographical distribution of AERONET sites used

Fig. 5. Aerosol extinction coefficient from the ground-based MPL during the CALIPSO overpass period. (a) 19:00 (LTC) on 21 December 2021; (b) 06:37 (LTC) on 17 June 2022 (The white dashed line indicates the CALIPSO overpass time，the blank space are low-quality and cloud-covered data.)

Fig. 6. Comparison of aerosol extinction profiles between MPL and CALIPSO.(a) 19:00 (LTC) on 21 December 2021;(b) 06:37 (LTC) on 17 June 2022

Fig. 7. Seasonal distribution of aerosol extinction coefficients vertical structure over sea and land in central region of Yangtze River Delta from 2013 to 2022. (a) Sea; (b) land

Fig. 8. Seasonal distribution of aerosol type occurrence frequency vertical structure over sea and land in central region of Yangtze River Delta from 2013 to 2022. (a) Sea; (b) land

Fig. 9. AOD boxplots and trends over the sea and land in central region of Yangtze River Delta from 2013 to 2022 (0–1 km altitude). (a) Sea; (b) land. (The red line represents the median, the upper and lower bounds of the box indicate the 75th percentile (Q3) and 25th percentile (Q1), respectively, and the upper and lower whiskers represent Q3 + 1.5 × IQR and Q1 - 1.5 × IQR. The black dashed line indicates the trend of AOD changes derived from linear fitting based on the mean values after excluding outliers)