Evaluation of the hyperspectral radiometer (HSR1) at the ARM SGP site

Abstract. The Peak Design Ltd hyperspectral radiometer (HSR1) was tested at the Atmospheric Radiation Measurement User Facility (ARM) Southern Great Plains (SGP) site in Lamont, Oklahoma for two months from May to July 2022. The HSR1 is a prototype instrument that measures total and diffuse spectral irradiance from 360 to 1100 nm with a spectral resolution of 3 nm. The HSR1 spectral irradiance measurements are compared to nearby collocated spectral radiometers including two multifilter rotating shadowband radiometers (MFRSR) and a shortwave array spectroradiometer—hemispheric (SASHe). The total spectral irradiances at 500 nm for the HSR1 compared to the MFRSRs have a mean (relative) difference of 0.01 W m^-2 nm^-1 (1–2 %). The HSR1 mean diffuse spectral irradiance at 500 nm is smaller than the MFRSRs by 0.03–0.04 (10 %) W m^-2 nm^-1. The HSR1 clear-sky aerosol optical depth (AOD) is also retrieved by considering Langley regressions and compared to collocated instruments such as the Cimel sunphotometer (CSPHOT), MFRSRs, and SASHe. The mean HSR1 spectral AOD at 500 nm is larger than the CSPHOT by 0.010 (8 %) and larger than the MFRSRs by 0.007–0.017 (6–18 %). In general, good agreement between the HSR1 and other instruments is found in terms of the spectral total irradiance, diffuse irradiance, and AODs at 500 nm. The HSR1 quantities are also compared at other wavelengths to the collocated instruments, where similar agreement is found for the spectral irradiances, although relatively larger disagreement is found at higher wavelengths, especially for spectral AODs.