Atmospheric aerosols are tiny particles floating in the air. Changes in aerosol optical depth (AOD) reflect rapid shifts in the atmosphere and are closely linked to air quality and climate processes. However, current observations and datasets still face challenges in balancing accuracy with full spatial and temporal coverage.

Recently, researchers from the Hefei Institutes of Physical Science of the Chinese Academy of Sciences analyzed 32 years of global ground-based observations from the Aerosol Robotic Network (AERONET), and studied how AOD changes throughout the day. The findings were published in Geophysical Research Letters.

Through long-term minute-level observations from AERONET, researchers identified eight typical patterns of how AOD varies within a day. These patterns have clear physical meaning and are closely related to land surface conditions and aerosol types, suggesting that local environments play an important role in shaping daily AOD behavior.

Besides, researchers evaluated the performance of current reanalysis datasets and model simulations in reproducing hourly AOD variations. They found that only about 12.7% of the global region can be well represented, and model performance varies by region: simulations match observations better in the morning in natural landscapes, while they match observations better in the afternoon in areas influenced by human activity.

The findings of this study will help improve air quality, optimize orbital design for atmospheric monitoring satellites, and improve climate model performance.