A new multispectral photometer for monitoring aerosol microphysical, optical, and radiative properties

Abstract

Abstract. A new multispectral photometer, named CW193, was proposed in this study for monitoring aerosol microphysical, optical, and radiative properties. The instrument has a highly integrated design, smart control performance, and is composed of three parts (an optical head, a robotic drive platform, and a stents system). Because of its low maintenance requirements, this instrument is appropriate for the deployment in remote and unpopulated regions. Based on the synchronous measurements, the CW193 products was validated using reference data from the AERONET CE318 photometer. The results show that the raw digital counts from CW193 agree well the counts from AERONET (R2 > 0.97), with daily average triplets of around 1.2 % to 3.0 % for the ultraviolet band and less than 2.0 % for the visible and infrared bands. A good aerosol optical depth agreement (R > 0.99, 100 % within expected error) and root mean square error (RMSE) values ranging from 0.006 (for the 870 nm band) to 0.016 (for 440 nm the band) are obtained, with a relative mean bias (RMB) ranging from 0.922 to 1.112 and an aerosol optical depth bias within ±0.04. The maximum deviations for fine-mode particles varied from about 8.9 % to 77.6 %, whereas the variation for coarse-mode particles was about 13.1 % to 29.1 %. The deviation variations of the single scattering albedo were approximately 0.1–1.8 %, 0.6–1.9 %, 0.1–2.6 %, and 0.8–3.5 % for the 440 nm, 675 nm, 870 nm, and 1020 nm bands, respectively. For the aerosol direct radiative forcing, deviations of approximately 4.8–12.3 % was obtained at the Earth’s surface and 5.4–15.9 % for the top of the atmosphere. In addition, the water vapor retrievals showed a satisfactory accuracy, characterized by a high R value (~0.997), a small RMSE (~0.020), and good expected error distribution (100 % within expected error). The water vapor RMB was about 0.979 and the biases mostly varied within ±0.04, whereas the mean values were concentrated within ±0.02.