**Acknowledgements**

**Figure 22.** An example of AOD distribution retrieved from CALIPSO data with the AOD at 532 nm (the left panel) and

The ground reflectance is significantly different over land and ocean, leading to the need for different approaches of the atmospheric correction in order to optimize the results. However, this difference can be expressed by the spectra of the LUT of in situ measurements in the UAC model. Based on the LUT of the ground reflectance, the aerosol reflectance can be obtained by the best nonlinear least square fit function based on the Angstrom law. The reflectance is then used to determine the epsilon spectra that are used to select the two closest aerosol models instead of one epsilon value from the NIR band. The results show that this approach is more robust to overcome the problem caused by small variations in the aerosol reflectance in the two NIR bands. Meanwhile, this approach can also reduce some abnormal epsilon errors caused by factors including the data quality of satellite reflectance and the mismatch between the actual ground reflectance and the LUT. The use of the LUT provides a unified approach for estimating the aerosol reflectance and the ground reflectance over land and ocean. The performance of the UAC model is evaluated using a SeaWiFS image. The results show that the model can completely separate the aerosol scattering reflectance from the radiance at TOA. The relative error is 22.1% when it is validated by the in situ measured AOT data using the MICROTOP instruments, and the error is 31.4% using the four sites of AERONET measured AOT data over the ECS in 2006 and 2007. The UAC model can provide the aerosol products

MODIS AOTs at 12 stations around China using the AERONET observations have been evaluated with the result that both agree generally well over ocean and land. The seasonal changes and spatial distributions of aerosol optical properties have also been observed with a notable

from satellite remote sensing data over land and ocean.

1064 nm (the right panel).

134 Aerosols - Science and Case Studies

**6. Conclusions**

This study is supported by the National Key Research and Development Program of China (2016YFC1400901), the National Science Foundation of China (41476156, 41321004), and the Public Science and Technology Research Funds Projects of Ocean (201005030), the Anhui research project in the Public Interest (1604f0804003), and the China Special Fund for Meteorological Research in the Public Interest (GYHY201406039). We thank our colleagues from the Second Institute of Oceanography SOA, who took part in the cruises, for their hard work on in situ measurements. We also want to thank the experts who provided us their in-situ measurements.
