Evaluation of the hyperspectral radiometer (HSR1) at the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site

<p>The Peak Design Ltd hyperspectral radiometer (HSR1) was tested at the Atmospheric Radiation Measurement (ARM) user facility Southern Great Plains (SGP) site in Lamont, Oklahoma, for 2 months from May to July 2022. The HSR1 is a prototype instrument that measures total (<span class="inline-formula"><i>F</i>_total</span>) and diffuse (<span class="inline-formula"><i>F</i>_diffuse</span>) 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 (MFRSRs) and the Shortwave Array Spectroradiometer–Hemispheric (SASHe) radiometer. The <span class="inline-formula"><i>F</i>_total</span> at 500 nm for the HSR1 compared to the MFRSRs has a mean (relative) difference of 0.01 W m<span class="inline-formula">⁻²</span> nm<span class="inline-formula">⁻¹</span> (1 %–2 %). The HSR1 mean <span class="inline-formula"><i>F</i>_diffuse</span> at 500 nm is smaller than the MFRSRs' by 0.03–0.04 (10 %) W m<span class="inline-formula">⁻²</span> nm<span class="inline-formula">⁻¹</span>. 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 AOD at 500 nm is larger than the CSPHOT's 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 <span class="inline-formula"><i>F</i>_total</span>, <span class="inline-formula"><i>F</i>_diffuse</span>, and AODs at 500 nm. The HSR1 quantities are also compared at other wavelengths to the collocated instruments. The comparisons are within <span class="inline-formula">∼</span> 10 % for the <span class="inline-formula"><i>F</i>_total</span> and <span class="inline-formula"><i>F</i>_diffuse</span>, except for 940 nm, where there is relatively larger disagreement. The AOD comparisons are within <span class="inline-formula">∼</span> 10 % at 415 and 440 nm; however, a relatively larger disagreement in the AOD comparison is found for higher wavelengths.</p>