Reading notes-4

Satellite-derived aerosol products provide long -term and large-scale observations for analysing aerosol distributions and variations, climate-scale aerosol simulations, and aerosol-climate interactions. Therefore, a better understanding of the consistencies and differences among multiple aerosol products is important.

The objective of this study is to compare 11 global monthly aerosol optical depth(AOD) products , which are the European Space Agency Climate Change Initiative(ESA-CCI) Advanced Along-Track Scanning Radiometer(AATSR), Advanced Very High Resolution Radiometer(AVHRR), Multi-angle Imaging SpectroRadiometer(MISR), Moderate Resolution Imaging Spectroradiometer(MODIS), Sea-viewing Wide Field-of-view Sensor(SeaWiFS),Visible Infrared Imaging Radiometer(VIIRS), and POLarization and Directionality of the Earth’s Reflectance(POLDER) products. AErosol RObotic NEtwork(AERONET) Version 3 Level 2.0 monthly measurements at 308 sites around the world are selected for comparison.

Our results illustrate that the spatial distributions and temporal variations of most aerosol products are highly consistent globally but exhibit certain differences on regional and site scales. In general, the AATSR Dual View(ADV) and SeaWiFS products show the lowest spatial coverage with numerous missing values, while the MODIS products can cover most areas(average of 87%) of the world. The best performance is observed in September-October-November(SON) and the worst is in June-July-August(JJA). All the products perform unsatisfactorily over northern Africa and Middle East, southern and eastern Asia, and their coastal areas due to the influence from surface brightness and human activities.

In general, the MODIS products show the best aggrement with the AERONET-based AOD values on different spatial scales among all the products. Furthermore, all aerosol products can capture the correct aerosol trends at most cases, especially in areas where aerosols change significantly. The MODIS products perform best in capturing the global temporal variations in aerosols. These results provide a reference for users to select appropriate aerosol products for their particular studies.

Our results may help readers to better understand the features of different satellite aerosol products and select a suitable aerosol dataset for their studies.

Furthermore, aerosol retrieval over highly bright and heterogeneous areas over land still have large estimation uncertainties, which brings great challenges due to high surface brightness and intense human activities. Therefore, the aerosol algorithm teams may need put more effort into optimizing the estimation in surface reflectance and the assumption of aerosol types over these areas to improve the data quality of aerosol retrievals and thus increase the spatial coverage and decrease the diversity among different data set. These could be the major points of aerosol research in the future.

Wei, J., Peng, Y., Mahmood, R., Sun, L., Guo, J., 2019e. Intercomparison in spatial distributions and temporal trends derived from multi-source satellite aerosol products. Atmos. Chem. Phys. 19 (10), 7183e7207.