High-Spectral-Resolution Retrieval of Ultraviolet and Visible Aerosol Optical Depth Using the Pandora Spectrometer

Atmospheric aerosols from natural and anthropogenic sources are a major component of air pollution and substantially affect air quality, human health, and atmospheric chemistry. Reliable and continuous aerosol optical depth (τaer) measurements from ground-based instruments are therefore essential for characterizing aerosol loading and its spatiotemporal variability. This study presents a framework for retrieving τaer in the UV (315–375 nm) and visible (400–530 nm) spectral ranges using the Pandora spectrometer. In the ultraviolet (UV) range, reliable τaer retrieval from standard direct-Sun measurements is hindered by out-of-band stray light from visible wavelengths. To address this limitation, this study utilizes measurements acquired with a U340 filter, which suppresses this contamination in UV spectra and enables reliable τaer retrievals in the UV region. Through the proposed spectral fitting framework, trace gas absorption and aerosol extinction components are successfully separated from the measured total optical depth. Concurrently, τaer values at visible wavelengths are retrieved from standard Diffuser measurements. The retrieved UV and visible τaer values show good agreement with collocated AErosol RObotic NETwork (AERONET) data, with R2 = 0.88–0.99, RMSE = 0.016–0.039, |MBE| = 0.002–0.023, slopes of 0.93–1.01, and |intercepts| < 0.01. Together with the trace gas products simultaneously retrieved by Pandora, these τaer datasets can serve as a valuable resource for air pollution analysis.