Measurements from three spectral instruments, the Solar Spectral Flux Radiometer (SSFR), the Rotating Shadowband Spectrometer (RSS), and the Solar Ultraviolet Spectroradiometer (SUV), are compared to results from the Santa Barbara Moderate Resolution Radiative Transfer Model (SBMOD). SSFR data are from the SHEBA experiment of May--June 1998. RSS and SUV data are from Barrow, Alaska, April 1999. SBMOD is a recently developed model utilizing the correlated-k method of computing gaseous absorption and convolves the solar source function and the instrument's filter function during computations. Comparisons indicate that absorption of ozone, water vapor, oxygen, and the O2-O2 absorption complexes are well characterized by the model. There does not appear to be any significant unexplained absorption between 0.4 and 1.0 microns, as evidenced by comparisons between SBMOD and both SSFR and RSS data. However, a more absorptive aerosol was required to reach agreement between SBMOD and RSS diffuse fields than we anticipated. Data from the RSS and SUV possess similar structure over their entire shared spectral range from 400 to 600 nm, and the RSS and SSFR possess similar structure between 500 and 1000 nm. However, below 500 nanometers, measurements from all three instruments diverge noticeably from model results. The residual between the SUV and RSS measurements and SBMOD are similar to those presented in prior studies, suggesting that there may be errors in several widely used representations of the solar spectrum between 400 and 500 nm. The shape of the SSFR's data in this region has yet to be fully explained; aspects of its calibration and operation may be the main source of uncertainty.