Employing relaxed smoothness constraints on imaginary part of refractive index in AERONET aerosol retrieval algorithm ...

• Main Authors: Sinyuk, Alexander, Holben, Bent, Eck, Thomas, Giles, David, Slutsker, Ilya, Dubovik, Oleg, Schafer, Joel, Smirnov, Alexander, Sorokin, Mikhail
• Format: Article in Journal/Newspaper
• Language: English
• Published: EGU 2022
• Subjects: Aerosol Robotic Network
• Online Access: https://dx.doi.org/10.13016/m2rbk0-wzfq; https://mdsoar.org/handle/11603/24542

In the Aerosol Robotic Network (AERONET) aerosol retrieval algorithm, smoothness constraints on the imaginary part of the refractive index (IPRI) provide control of retrieved spectral dependence of aerosol absorption by preventing the inversion code from fitting the noise in optical measurements and thus avoiding unrealistic oscillations of retrievals with wavelength. The history of implementation of the IPRI smoothness constraints in the AERONET aerosol retrieval algorithm is discussed. It is shown that the latest version of the IPRI smoothness constraints, termed standard (STD) and employed by Version 3 (V3) of aerosol retrieval algorithm, should be modified to account for strong variability of light absorption by brown carbon (BrC) containing aerosols in UV through mid-visible parts of the solar spectrum. In V3 strong spectral constraints were imposed at high values of the Angstrom Exponent (AE; 440–870 nm) since black carbon (BC) was assumed to be the primary absorber, while the constraints became ...