Evaluation of satellite dust-related products using ground-based remote sensing techniques

Accurate monitoring of dust is important for studying its impacts on human health, the environment, and climate change. The IASI (Infrared Atmospheric Sounding Interferometer) instrument, which is on board the MetOp satellites in polar orbit, was first launched in 2006 and currently has two instruments in orbit. Among other products, it provides two datasets related to desert dust. The first is a dust flag, which indicates the presence of dust particles based on specific index values, as well as the quantity of those particles. The second is the atmospheric dust optical depth, a parameter derived from the estimated profile of dust particle concentration and its integration. In the first part of this study, the dust index product is evaluated using measurements from CIMEL sun photometers around the Mediterranean Sea, as collected by the AERONET (AErosol RObotic NETwork) network. For this purpose, an aerosol classification methodology is applied, using the Angstrom Exponent and the Aerosol Optical Depth (AOD). Only satellite pixels close to AERONET stations are used, along with measurements taken within a 60-minute time difference between instruments, to ensure that atmospheric conditions are as stable as possible. The results of the study show a positive agreement between IASI and CIMEL data. The information on aerosol quantity, which is also provided by the dust flag, is assessed in relation to variations in AOD and AE. Next, the Dust Optical Depth (DOD) product from IASI is compared with Lidar (Light Detection and Ranging) measurements conducted at the Laboratory of Atmospheric Physics (LAP) of the Department of Physics at Aristotle University of Thessaloniki (AUTH). Using the POLIPHON (POlarization LIdar PHOtometer Networking) method, which is based on appropriate threshold values of the depolarization ratio derived from lidar, it is possible to calculate the dust optical depth from an extinction profile. These estimates are then compared with the values provided by IASI for specific dust episodes over Thessaloniki. The results indicate that, although the agreement is satisfactory, more cases need to be examined for a comprehensive evaluation. In a second part, certain profiles provided by the satellite are qualitatively compared with corresponding concentration profiles from the Lidar, following appropriate processing.