Ground-based radiometers with extended spectral coverage: evaluation and expected applications

Airborne and satellite observations have successfully extracted a wealth of information about clouds, aerosols, and the Earth’s surface. These observations can be significantly complemented by the long-term ground-based radiation data provided by the Multi-Filter Rotating Shadowband Radiometers (MFRSRs) supported by the U.S. Department of Energy’s (DOE) Atmospheric Radiation Measurement (ARM) Program. Until recently, ARM-supported MFRSRs measured total irradiance and its direct and diffuse components at six wavelengths (415, 500, 615, 675, 870, and 940 nm). The limited number of wavelengths and the narrow spectral range of these MFRSRs prevent improved retrievals of aerosol, cloud, and surface characteristics. For example, spectrally resolved aerosol optical depth derived from the direct irradiance measured across a wide spectral range offer a valuable avenue for improved estimations of aerosol size distributions, especially for large particles. To address these limitations, ARM has supported the development of two successors to the MFRSR. The first, the MFRSR-7nch, includes a seventh narrowband channel at a 1625 nm wavelength, while the second, the Shortwave Array Spectroradiometer-Hemispheric (SAS-He), features increased spectral coverage (350-1700 nm) and hyperspectral capabilities. The performance of these successors is thoroughly evaluated under a wide range of atmospheric conditions, including different aerosol and cloud types and significant variability in aerosol loading. Our presentation will highlight the design, evaluation, and anticipated applications of these advanced radiometers.