Consistency of multiple Aerosol Optical Depth retrievals from satellite data

This study addresses the critical issue of accurately measuring Aerosol Optical Depth (AOD) from satellite data, given the significant impact of aerosols on climate. Aerosols and clouds contribute the largest uncertainty to Earth's radiative forcing estimates, as stated by the IPCC. The study utilizes data from the Copernicus Climate Change Service and focuses on AOD retrieval using Dual-View Instruments (ATSR2, AATSR, SLSTR) and the Infrared Atmospheric Sounding Interferometer (IASI), specifically for Dust AOD.

Due to the under-determined nature of the AOD retrieval process, assumptions about aerosol properties and Earth's surface are necessary. Furthermore, cloud masking needs to be done prior to the retrieval since even spurious cloud contamination can lead to significant AOD errors. Consistency among different algorithms and instruments is crucial for reliable conclusions. Analyzing data from Dual-View Instruments and IASI, the research examines the varying levels of consistency among different algorithms.  

For these metrics, 5x5° global maps are provided for each metric. Defining a minimal threshold for each of the 4 metrics, an overall count of fulfilled consistency criteria (ranging from 0 to 4) is calculated as ultimate quantity.  Low consistency (total number of fulfilled criteria below 3) is then an indicator for a higher level of difficulty in retrieving AOD, while areas with high consistency (3 or 4) are considered more reliable. Such a consistency map helps aerosol retrieval experts to focus critical examination of their algorithms while research using the satellite aerosol data records can base their analysis on well-founded quality statements. It is important to point out that there is no perfect algorithm to this day since each of them has their strengths and weaknesses under specific conditions.