Multi-spectral automated rotating shadowband radiometry in the Atmospheric Radiation Measurement (ARM) Program

This paper discusses the work in progress to develop two RSR variants that extend this measurement technique to make measurements at multiple wavelengths. One of these instruments uses independent interference-filter/photodiode detectors to measure any seven wavelength bands chosen between 350 nm and 2.5 {micro}m, and the other uses a prism spectrograph coupled to a Charge-Coupled Device (CCD) array to measure 256 wavelength intervals from 370 nm to 1 {micro}m. These instruments provide spectrally resolved measurements of the direct-normal, total horizontal, and diffuse horizontal irradiances. These parameters of the sky-radiance function are measured using the same detector (for a given wavelength), eliminating the difficulties inherent in comparing these data when they are taken by independent detectors. The data are measured synchronously, and can be measured at intervals as short as 10 seconds if desired, though more normally data are taken at 15 second intervals and averaged over 1 to 5 minutes. Field deployment of the multiple filter instruments has begun, and twelve of these instruments will be deployed this year as part of the United States Department of Energy (DOE) Quantitative Links measurement program. In addition, further development and testing of these instruments is underway as part of the Atmospheric Radiation Measurement Program also sponsored by DOE