SI-traceable solar irradiance measurements for aerosol optical depth retrieval

Abstract The overall aim of this study is to enable the traceable International System Units (SI) determination column-integrated aerosol optical depth (AOD) retrieved from passive remote sensing atmosphere using SI-traceable direct solar spectral irradiance measurements. A precision filter radiometer that measures for retrieval AOD has been characterized and calibrated at state-of-the-art calibration facilities Physikalisch-Technische Bundesanstalt. measured irradiances together with three top-of-the-atmosphere (TOA) spectra have used retrieving AODs, which were validated against reference instruments World Aerosol Optical Depth Calibration Centre Meteorological Organization (WMO). factors agreed within ±0.57% (3 ? ) all TOA except 368 nm (?1.1%) 862 (1.8%) channels one out spectra. Application these results showed differences current methods/instruments well recommended WMO limits. work provides a first step opening new era measurements traceability, providing link SI through laboratory-based approach, main advantages being low uncertainty, possibility enhancing global homogenization efforts chance avoid activities based on instrument relocations.